maarec/penn state extension materials

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ISSN1814-1137

AGRICULTURALAND FOOD

ENGINEERINGTECHNICAL REPORT

Honey bee diseases and pests:a practical guide

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iii

Contents

Foreword vii

Acknowledgements viii

1. Introduction 1

2. Microbial diseases 3

2.1 Bacterial diseases 3

American foulbrood disease (AFB) 3

European foulbrood disease (EFB) 5

2.2 Fungal disease 6

Chalkbrood disease (Ascosphaerosis) 6

2.3 Viral diseases 7

Sacbrood disease 7

2.4 Protozoan disease 8

Nosema disease (Nosemosis) 8

3. Parasitic bee mites 11

3.1 Varroa mite (Varroasis) 11

Cause 11

Symptoms 12

Chemical control 13

Etheric oils 14

Synthetic chemicals 14

Control by hive manipulation 15

3.2 Tropilaelaps mite 15

Cause 15

Symptoms 15

Control 16

Chemical control 16

Colony manipulation techniques 16

3.3 Tracheal mite (Acarapidosis) 17

Cause 17

Symptoms 17

Control 17

4. Insects 19

4.1 Beetle 19

Small hive beetle (SHB) 19

4.2 Ants 20

Control 20

4.3 Wasps and hornets 20

Control 21

4.4 Wax moths and other Lepidoptera 21

The greater wax moth (Galleria mellonella) 21


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iv

The lesser wax moth (Achroia grisella) 22

Other Lepidoptera 23

5. Vertebrates 25

5.1 Amphibians 25Control 25

5.2 Reptiles 25

Control 26

5.3 Birds 26

Control 26

5.4 Mammals 26

6. Honey bee introduction and quarantine 29

7. General measures for bee protection 31Other measures 31

References 33


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v

List of plates

1. Irregular pattern of sealed brood with sunken and punctured caps,typifying American foulbrood infestation. 3

2. Stretch test for American foulbrood disease. 4

3. Larvae in coiled stage, killed by European foulbrood disease. 5

4. Brood killed by chalkbrood: white and black mummies. 6

5. Honey bee larvae killed by sacbrood disease. 7

6. Nosema apis spores (magnification factor 400 x). 8

7. Varroa mite showing nymphal stages and male. 12

8. Bee larvae with varroa mites. 139. Adult female of Tropilaelaps spp. 14

10. Adult female of Tropilaelaps spp. onA. mellifera pupa. 15

11. Parasitism by Varroa jacobsoniior Tropilaelaps clareae usuallyresults in deformation of the bees wings. 16

12. Tracheal mite,Acarapis woodi. 17

13. Small hive beetle. 19

14. Small hive beetle larvae. 19

15. Apis millifera colony invaded by Vespa tropica. 21

16. Comparative body sizes of (left) Vespa tropicaand (right, top to bottom)Apis florea,A. cerana andA. dorsata. 21

17. Best prevention of wax moths: keeping the apiary clean. 22

18. Brood surface (open cells with immature pupae) changed by wax moth. 23


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vi

List of boxes

1. Stretch test 4

2. Heat treatment and fumigation 9

3. Organic acids 13

List of figures

1. Predation by toads on a honey bee colony 25

2. Predation on honey bees by a lizard 26

List of tables

1. Bee mites and their hosts 11

2. Wasps and hornets that attack bees in Asia 20


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vii

Foreword

Honey bees play a vital role in the environment by pollinating both wild flowers andmany agricultural crops as they forage for nectar and pollen, in addition to producinghoney and beeswax. The essential and valuable activities of bees depend uponbeekeepers maintaining a healthy population of honey bees, because like other insectsand livestock, honey bees are subject to many diseases and pests.

The apiculture industry plays an important role in generating employment and inincreasing family income in the rural areas of the world. Many developing countriesare trying to improve the quality of their honey products but they frequentlyencounter the main obstacle in apiculture; control of diseases and pests of honey bees.

Therefore, it is very important to publish a practical guide for beekeepers andtechnicians of apiculture in order to control and prevent the diseases and pests ofhoney bees. This report provides the basic and practical technology applicable tobeekeepers in the world on the importance of various pests and diseases of honey bee.

This practical guide to honey bee diseases and pests by Wolfgang Ritter andPongthep Akratanakul is the revised edition of Honey bee diseases and enemies inAsia, published by FAO in 1987 as Agricultural Services Bulletin No. 68/5, and hasbeen prepared under the auspices of the FAO programme on Enhancing Food Qualityand Safety by Strengthening Handling, Processing and Marketing in the Food Chain.

The publication is further evidence of the continuing endeavours of FAO to promotebeekeeping in developing countries as a low-cost means of improving local diets, increasingrural industry and purchasing power and diversifying sources of foreign exchange.


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viii

Acknowledgements

Special thanks go to FAO for giving us the opportunity to share our knowledgeand experience in apiculture industry development in the world. We particularlywish to express our sincere gratitude to the technical officers of the Agricultural andFood Engineering Technologies Service (FAO) for their valuable contributions andsuggestions to improve and enrich this work.

Special thanks go to David Ryde for editing the report, and Larissa DAquilio forthe desktop publishing.


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1

Chapter 1

Introduction

All living organisms are subject to infestation orattack by their natural enemies, and honey beesof the genusApis are no exception. Through theirlong history of evolution and natural selection,they have achieved a high level of eusociality,many thousands of individual bees living

together in a tightly knit social organization.Since individual bees have more than frequentcontact among themselves, and since trophyllaxis(the sharing and orally passing of food amongmembers of the nest) is one of the most importantand frequent aspects of the bees' social behaviour-- in that it allows hormones and pheromones tobe widely distributed throughout the colony--whenever a pathogenic organism is present in thecolony it will be spread with great ease.

The effective defense against disease is one ofthe most essential achievements of the bee colony.

The individual bees immune system functions in asimilar way to that of vertebrate animals, althoughthe most effective defense mechanism that canlead to self-healing of the bee colony is the socialbehaviour of removing as many pathogen agentsor parasites as possible from the bee colony.

This behavioural defence (entrance reductionand/or stinging) prevents parasites frompenetrating the bee colonies, or their killing orremoval. If the dead organism is too large toremove, as with mice, the bees completely cover

it with propolis. This prevents release of thepathogens during decomposition of the body.Propolis is also applied inside the brood cellsbefore new brood is reared. Disinfection of theinside of the cell is effected by covering withsecretion from the mandible and propolis.

The most important defence against disease,however, is the bees hygiene behaviour. Thedefence against brood diseases comprisesidentification and removal of affected brood. Tothis end the bees inspect every single brood cell.On finding an infected larva in a sealed cell, thecell capping is removed, and any sick brood isremoved and finally eliminated from the colony.The beekeeper recognises defence activities against

brood diseases from the scattered brood surface.If adult bees fall ill they are either forced to leave

the colony or are lost during the first foraging flight.Self-healing is therefore frequently possible byincreasing flight activity. This may be initiated byforaging flights or during hibernation by cleansing

flights, although it is only possible if the colony issufficiently provided with pollen and nectar.Despite these very effective defence

mechanisms, diseases, parasites and destructiveinsects may represent a problem for bee colonies.Diseases may be spread by migration and sale ofcolonies, equipment and/or bees. With increasingglobalization, bee colonies are transported overgreat distances and even between continents, in thisway foreign species and their diseases are spread.

While the question of exactly how manyspecies of honey bees of the genusApis exist

continues to be a subject of debate amongtaxonomists, there are at least three commonlyrecognized groups native to Asia. These aretheApis dorsata group (commonly called rockbees or giant honey bees), theApis florea group(commonly called dwarf or midget honey bees)and theApis cerana group (commonly calledoriental honey bees. This group includes theIndian honey bee, Chinese bee, Japanese bee).

The introduction of the common or Europeanhoney bee (Apis mellifera) into Asia increases

the total number of distinct species on thecontinent. However, new pathogen agents suchasAcarapis woodi have been imported into Asiawith the introduction of the European bee. Onthe other hand, parasites like Varroa destructoror Tropilaelaps spp. have managed to transitfrom their original hosts to the new bee species.This has completely changed the scenario of beediseases forApis mellifera in Asia and throughoutthe rest of the world. Viruses have been spread byApis mellifera beekeepers migrating or shippingbees to new areas and infecting and sometimesdecimatingApis cerana colonies. In view of thefact that all bee species in Asia often occupy thesame areas the problem of disease has become


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especially urgent. A number of serious outbreaksof native diseases have already been caused in newareas resulting in immeasurable economic costs tosmall and large beekeepers alike.


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3

Chapter 2

Microbial diseases

2.1 BACTERIAL DISEASES

American foulbrood disease (AFB)Beekeepers in temperate and sub-tropical regionsaround the world generally regard Americanfoulbrood (AFB) as possibly the most destructive

microbial disease affecting bee brood. Thedisease did not originate in, nor is it confinedto, the Americas. It is widely distributedwherever colonies ofApis mellifera are kept. Intropical Asia, where sunlight is abundant andtemperatures are relatively high throughout theyear, the disease seldom causes severe damage tobeekeeping operations. The disease is contagiousand the pathogenic bacterium can remaindormant for as much as and more than 50 years.Therefore, beekeepers and extension specialiststhroughout Asia should be acquainted with the

symptoms of this disease and know how to copewith it should the need arise.

CauseAmerican foulbrood disease is caused by aspore-forming bacterium, Paenibacilluslarvae,which only affects bee brood; adult bees are safefrom infection. At the initial stage of colonyinfection, only a few dead older larvae or pupaewill be observed. Subsequently, if remedialaction is not taken, the disease will spread within

the colony and can quickly spread to othercolonies in the apiary as a result of robbing,drifting workers, or contamination caused by thebeekeeper's hive manipulations.

In the same way the pathogen agent can spreadto other apiaries. Natural transfer mainly takes

place within a radius of 1 km around the apiary.Often spores enter the bee colonies via foreignhoney. Commercially available honey may behighly contaminated; therefore, special attentionshould be paid near honey processing enterprisesand waste disposal sites.

SymptomsAt the initial stage of AFB infection, isolatedcapped cells from which brood has not emergedcan be seen on the comb. The caps of these deadbrood cells are usually darker than the caps of

healthy cells, sunken, and often punctured. Onthe other hand the caps of healthy brood cellsare slightly protruding and fully closed. As thedisease spreads within the colony, a scattered,irregular pattern of sealed and unsealed broodcells (see Plate 1) can be easily distinguished fromthe normal, compact pattern of healthy broodcells observed in healthy colonies.

The bee brood affected by AFB is usuallyat the stage of older sealed larvae or youngpupae, upright in the cells. Often therefore,

a protruding tongue can be found with therest of the body already decayed. At firstthe dead brood is dull white in colour, but itgradually changes to light brown, coffee brown,and finally dark brown or almost black. Theconsistency of the decaying brood is soft.

Once the dead brood have dried into scales,the test cannot be used. The dry brood lies flat onthe lower side of the cell wall, adhering closely toit in contrast to sacbrood. This scale is usuallyblack or dark brown and brittle. Often, a fine,threadlike proboscis or tongue of the dead pupacan be seen protruding from the scale, anglingtoward the upper cell wall.

The pathogen bacteria may be identified using

Plate 1Irregular pattern of sealed brood with sunken andpunctured caps, typifying American foulbrood infestation.

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Honey bee diseases and pests: a practical guide4

a microscopic preparation or, more frequently,by cultivation on selective culture media. TheColumbia slant culture has proved to be mosteffective for this purpose. The result is controlledby biochemical or serological tests and moreoften by means of the Polymerase Chain Reaction(PCR). As PCR is very sensitive its suitability isrestricted regarding the direct evidence in combsamples (see OIE Manual of Diagnostics, 2004).

Commercially available AFB diagnosing kitsare based on serological evidence of the pathogen

agent. In general, they are appropriate for fielduse. But if there are clinically indifferent cases,misinterpretations may occur.

The examination of samples from stored foodof sealed brood combs has become importantin diagnosing AFB, although it is not effectivein detecting evidence of an outbreak of AFB.However, it is suitable for population screenings inapiaries and in determining the pathogen pressurein the individual colonies. The diagnostic reliabilityof the samples from the food wreath depends on the

quality of sample extraction. If samples are takenfrom newly gathered food or from other areas thanthe sealed brood combs, wrong diagnoses might bemade resulting in false negative results.

ControlIn several countries, where apiculture includeslarge commercial operations, frequent, efficientinspection services are particularly advancedand a search and destroy strategy may beadopted in an attempt to minimize damage toapiaries caused by this serious honey bee disease.The procedure involves hive inspections byqualified apiary inspectors. The entire honeybee population that is infected by American

foulbrood is killed and hive materials belongingto the colony, are disinfected or destroyed byburning. The bees are usually killed by poisonousgas such as the burning of sulphur powder. All

the dead bees, the frames, the supers, the honeyand the contaminated equipment are thrown intoa 1m x 1m x 1m hole in the ground. Keroseneis poured over the pile and set alight. When allthe material has been completely burned, thehole is carefully filled in, to prevent worker beesbelonging to healthy colonies from robbing anyremaining contaminated honey.

Although the above-mentioned methodhas proven effective, the practice of burningAFB infected colonies and equipment is costly,

especially taking into account the high cost ofbeekeeping equipment. The destruction of broodcombs and food combs is absolutely necessaryas, apart from the bees, they are the main carriersof spores. Dry combs, without brood, can bepreserved if an examination of wax samples in thelaboratory does not reveal Paenibacillus spores.Inwhich case the dry combs must also be destroyed.Old hives should be burned. Well conserved hives,however, should be disinfected. The inner part of ahive, once carefully cleaned, can quickly be singedout with the flame of a gas burner. The wooden

surface should look slightly brownish. When thisis not possible, e.g. if the hive is made from plastic,they should be cleaned and brushed with 3 to5 percent sodium hydroxide. Before using othersubstances for disinfection you should make surethat no residues remain that could be dangerous tobees or the consumer of the processed honey.

The killing of the bees can be avoided if the

BOX 1

Stretch test

A simple way of determining whether AFB

caused the death of the brood is the stretch test

(see Plate 2). A small stick, match or toothpick

is inserted into the body of the decayed larva

and then gently and slowly, withdrawn. If the

disease is present, the dead larva will adhere to

the tip of the stick, stretching for up to 2.5 cm

before breaking and snapping back in a somewhat

elastic way. This symptom called ropiness,

typifies American foulbrood disease, but it can be

observed in decaying brood only.

Plate 2Stretch test for American foulbrood disease.* Irregular pattern of sealed brood with sunken andpunctured caps, typifying American Foulbrood infestation.

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Chapter 2 - Microbial diseases 5

artificial swarm method is applied. A traditionalmethod is to keep the bee colony in a darkenvironment for several days. The bees are pushedinto a decontaminated hive with new combs, the

bee entrance is closed and they are placed in adark preferably quite cool room. Within two days,the bees have used up the contaminated food. Thecolonies can then be placed either at their formerstand or within a distance of at least 3 km away. Ifthe bees are kept in the dark for three days theyforget their old stand and can be placed anywhere.On the third day, however, some food shortagemay occur. Therefore, the colonies should be fed.

The direct artificial swarm method is lesscomplicated. First, a clean, decontaminated hive is

prepared. Instead of combs it contains three to sixwooden bars, depending on the colonys strength,provided with a wax strip as a starter for furthercomb construction. Using a queen excluder fixedat the entrance or above the bottom of the hiveshould prevent disappearance of the queen. Theprepared hive is placed at the colonys old standsubject to sanitation. Now the bees are pushedor brushed into the empty hive. Three days later,the combs that have been partially constructed bythe bees are removed again and burned. Combswith midribs later replace these. Now sanitation

is finished. The combs and the hive of the oldcolony are burned or decontaminated.

In some countries, beekeepers who destroytheir AFB-infected colonies receive compensation,either directly from the government or frombeekeepers organizations.

Chemotherapeutic methods of controllingAFB involve the administration of antibiotics orsodium sulfathiazole, in various formulations, fedmixed with powdered sugar or sugar syrup.

Antibiotics and sulfonamides prevent

multiplication of the agent, though it will notkill the spores. Therefore, multiplication maybegin again shortly after treatment, which is whytreatment must be repeated in shorter and shorterintervals. Over time the inner part of the hive,the food and honey become increasinglycontaminated by spores. Stopping treatmentwithout simultaneous disinfection leadsirrevocably to a relapse. However, detectableresidues remain even after a period of time haselapsed between treatment and honey extraction.

European foulbrood disease (EFB)As with American foulbrood disease, the name ofthis bacterial bee brood disease is inappropriate.

The range of distribution of European foulbrooddisease is not confined to Europe alone and thedisease is found in all continents whereApismellifera colonies are kept. Reports from India

indicate thatA. cerana colonies are also subject toEFB infection. The damage inflicted on honey beecolonies by the disease is variable. EFB is generallyconsidered less virulent than AFB; althoughgreater losses in commercial colonies have beenrecorded in some areas resulting from EFB.

CauseThe pathogenic bacterium of EFB isMellissococcus pluton. It is lanceolate in shape andoccurs singly, in chains of varying lengths, or in

clusters. The bacterium is Gram-positive and doesnot form spores. While many strains ofM. plutonare known, all are closely related.

SymptomsHoney bee larvae killed by EFB are youngerthan those killed by AFB. Generally speaking,the diseased larvae die when they are four to fivedays old, or in the coiled stage. The colour of thelarva changes at it decays from shiny white to paleyellow and then to brown. When dry, the scales oflarvae killed by EFB, in contrast to AFB scales, do

not adhere to the cell walls and can be removedwith ease. The texture of the scales is rubberyrather than brittle, as with AFB. A sour odour canbe detected from the decayed larvae. The clinicalpicture and the odour can vary depending on thekind of other bacteria involved (Bacillus alvei,Streptococcus faecalis, Achromobacter eurydice).Another symptom that is characteristic of EFBis that most of the affected larvae die before theircells are capped. The sick larvae appear somewhatdisplaced in the cells (see Plate 3).

Plate 3Larvae in coiled stage, killed by Europeanfoulbrood disease.

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When a scattered pattern of sealed and unsealedbrood is observed in a diseased colony, this isnormally an indication that the colony has reached

a serious stage of infection and may be significantlyweakened. However, this is the case with all brooddiseases. EFB is transferred in the same way asAFB. Melissococcus pluton as a permanent form,does not form spores but capsules which are lessresistant than the spores ofP. larvae.

The detection ofM.pluton is normally carriedout microbiologically. Selective culture media (OIE,2004; Bailey and Ball, 1991) are most appropriate.For further verification biochemical tests or thePCR can be applied. The gene technological test

is very sensitive and is therefore less suitable forthe detection ofM. pluton in suspicious brood. Asingle-use test set is commercially available basedon a serological proof like the AFB test set (seeOIE Manual of Diagnostics, 2004).

ControlThe choice of an EFB control method depends onthe strength of the infection, i.e. how many broodcells and combs are infested. If the infectionis weak, it is often sufficient to stimulate thehygiene behaviour of the bees. Either they areplaced at a good foraging site or they are fedwith honey or sugar water. An even better resultis achieved if the individual combs are sprayed

with a thinned honey solution. If the infestationis stronger it makes sense to reduce the numberof pathogens in the colony by removing the mostinfested brood combs. Empty combs or healthy

brood combs then replace these. Since the beeshygiene behaviour is also genetically determined,replacement of the queen is also possible. Re-queening can strengthen the colony by givingit a better egg-laying queen, thus increasing itsresistance to the disease and interrupting theongoing brood cycle giving the house bees enoughtime to remove infected larvae from the hive. Inserious cases, the same methods can be used asfor AFB. Sometimes chemotherapeutic measuressuch as antibiotics are called for, however, their

application, always risks the danger of residues.

2.2 FUNGAL DISEASE

Chalkbrood disease (Ascosphaerosis)In Asia, chalkbrood is rarely considered tobe a serious honey bee disease, although in

Japan the disease has been reported to causeproblems to beekeepers. In temperate Americaand Europe, however, cases have occurred inwhich chalkbrood has caused serious damage tobeekeeping; therefore, Asian beekeepers should

be aware of this problem.

CauseChalkbrood is a disease caused by the fungusAscosphaera apis. As its name implies, it affectshoney bee brood. This fungus only forms sporesduring sexual reproduction. Infection by sporesof the fungus is usually observed in larvae that isthree to four days old. The spores are absorbedeither via food or the body surface.

SymptomsInitially, the dead larvae swell to the size of the celland are covered with the whitish mycelia of thefungus. Subsequently, the dead larvae mummify,harden, shrink and appear chalklike. The colourof the dead larvae varies with the stage of growthof the mycelia: first white, then grey and finally,when the fruiting bodies are formed, black (seePlate 4). When infestation is heavy, much of thesealed brood dies and dries out within their cells.When such combs are shaken the mummifiedlarvae make a rattling sound. In the laboratory thefungus can be identified by its morphology (seeOIE Manual of Diagnostics, 2004).

Plate 4Brood killed by chalkbrood: white and black mummies.

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ControlAs with other brood diseases, the bees removethe infested brood with their hygiene behaviour(see European foulbrood), which is especially

effective for white mummies. Though as soonas the fruit bodies ofA. apis have developed,cleaning honey bees spread the spores withinthe colony by this behaviour. During the whitemummy stage the fungus continues to develop atthe hive bottom. If the mummies are not removedquickly, the spores may enter the brood cellscarried there by circulating air.

The beekeeper can stimulate the hygienebehaviour of the bees by changing the brood-rearing conditions. In this respect, it is most

important to adapt the size of the hive to thestrength of the bee colony. In this way the bees havea chance to inspect and clean the many brood cells.

Therefore, in most cases, the method ofstimulating hygiene behaviour, already describedunder European foulbrood control, is sufficientfor chalkbrood control. The beekeeper shouldensure that the colony has a strong workerpopulation, and that the hive is well ventilated andfree from accumulated moisture. At early stages ofchalkbrood infection, adding young adult workersand hatching brood, combined with sugar-syrup

feeding, often proves to be helpful.Currently there is no known successful

chemical control against chalkbrood. Itmeans that chemical treatment shows a littleeffect to control chalkbrood.In most cases,commercialised substances only show a positiveeffect because they are sprayed, or fed with sugarwater as described above.

2.3 VIRAL DISEASESOver the past years at least 18 virus types and

strains have been recorded as disease pathogensof adult bees and bee brood, nearly all are RNAviruses. Laboratory examination for virus diseasesis difficult, calling for sophisticated equipment andprocedures, since particles of the virus are too smallto be observed with ordinary light microscopes.However, they can rarely be differentiated withan electron microscope. Apart from serologicalmethods, most of the known viruses can now beidentified by genetic technologies (PCR).

The damage caused to colonies by viral infectionvaries considerably according to a number of factors,which include the type and strain of virus involved,the strength of the colony, weather conditions,the season and food availability. Basically, bees are

well-protected against infection with their chitinbody shell and gut coating. Parasitic mites suckingthe blood of the bees, however, can penetrate thisprotection. Therefore, increased infestation by

parasites is often accompanied by increased virusinfection. Little known viruses such as AcuteParalyses Bee Virus (APBV), and Deformed WingVirus (DWV) may become increasingly destructivein the future. As not much is known about the lifecycle and pathogenity of most virus diseases, thereare only a few ways to control them. Therefore,reflecting this situation, only the most widespreadsacbrood is described.

Sacbrood disease

Sacbrood disease (caused by Morator aetotulas)is perhaps the most common viral disease ofhoney bees. In Asia, at least two major typeshave been recorded. Sacbrood disease that affectsthe common honey beeApis mellifera and thesacbrood disease of the Asian hive beeA. cerana.A new type of sacbrood virus has recently beenreported in Asian colonies ofA.cerana. It ishighly probable that the virus is native to thecontinent and that it has been with the Asian hivebees over the long period of its evolution. Sinceits first discovery in Thailand in 1981, it has been

found in association withA. cerana in India,

Plate 5Honey bee larvae killed by sacbrood disease.

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Pakistan, Nepal, and perhaps all other countries inAsia within the honey bees range of distribution.Several reports indicate that nurse bees are thevectors of the disease. Larvae are infected via

brood-food gland secretions of worker bees.

SymptomsField inspection to determine whether thepathogenic virus has infected a colonycan beeasily carried out following symptomology.

Diseased larvae fail to pupate after fourdays; they remain stretched out on their backswithin their cells (distinct from the mostlytwisted position of larvae affected by Europeanfoulbrood. The anterior section of the larva,

consisting of its head and thorax, is the first partof its body to change colour, changing from whiteto pale yellow and finally to dark brown andblack (see Plate 5). On removing the larvae fromtheir cell the inspector can easily observe thattheir skin is quite tough and that its contents arewatery; the infected larva thus has the appearanceof a small, watery sac. Dead larvae remainingwithin their cells eventually dry out to flat scalesthat adhere loosely to the cell floor.

Control

No chemotherapeutic agent is effective inpreventing or controlling sacbrood disease.Colonies often recover from the infection withoutthe beekeeper's intervention, particularly if theinfection is not new to the geographic area. Thismainly depends on the hygiene behaviour of thebees, which may be stimulated as with other brooddiseases (see European foulbrood). Since the diseaseusually occurs when the colony is under stress(shortage of food, food-storage space, unfavourableclimatic conditions such as damp during the rainy

or cold season, unhygienic hive interior, poorqueen, infestation with other diseases, etc.), thebeekeeper should deal with severe cases by re-queening the colony, removing infected brood

combs and taking other management measures torestore colony strength, such as providing food andadding worker population. If there is an extremelystrong infestation it may be convenient to apply theartificial swarm method as for American foulbrood.

2.4 PROTOZOAN DISEASE

Nosema disease (Nosemosis)Nosema disease is generally regarded as one of themost destructive diseases of adult bees, affecting

workers, queens and drones alike. Seriouslyaffected worker bees are unable to fly and maycrawl about at the hive entrance or stand tremblingon top of the frames. The bees appear to agephysiologically: their life-span is much shortenedand their hypopharyngeal glands deteriorate, theresult is a rapid dwindling of colony strength.Other important effects are abnormally high ratesof winter losses and queen supersedures.

In climates with pronounced long periodsof flight restrictions, i.e. no flight opportunitieseven for a day, the infection easily reaches a

severe stage that visibly affects the strength ofthe colony. Less obvious infection levels in otherclimates often go undetected.

The damage caused by Nosema disease shouldnot be judged by its effect on individual coloniesalone as collectively it can cause great losses inapiary productivity.

CauseThe disease is caused by the protozoanNosemaapis, whose 5 to 7 mm spores infest the bees,

are absorbed with the food and germinate in themidgut. After penetration into the gut wall thecells multiply forming new spores that infect newgut cells or can be defecated. The nutrition of thebees is impaired, particularly protein metabolism.

SymptomsUnfortunately, there is no reliable field diagnosticsymptom enabling a diseased worker bee to beidentified without killing it, nor can the beekeeperrecognize an infected queen. However, in severecases of infection, it is sometimes possible toseparate healthy from diseased bees, the abdomenof an infected worker often being swollen andshiny in appearance. On dissection, the individual

Plate 6Nosema apis spores (magnification factor 400 x).

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circular constrictions in the alimentary canalsof uninfected bees are clearly visible, while theconstrictions cannot be seen clearly in diseasedbees. Easy separation, after killing, of firstabdominal segments with intestines attached,which shows white if strongly infected, versus anormal transparent, darker grey/ochre colour ifthere is no or only a low infection.

The most reliable method of detecting Nosemadisease involves laboratory procedures using amicroscope for diagnosis. A simple diagnosticmethod used for adult workers is to use a sampleof 20 suspected workers. The bees are killed, andtheir abdomens are removed and ground in water(2 to 3 ml per sample). A drop of the suspensionof pulverized bee abdomens is then viewed undera microscope. If the disease is present, reasonablylarge individual bacilliform spores with bright,queens egg-laying capacity fluorescent edges (seePlate 6) will be observed. In the visual field of themicroscope, at a 400 fold magnification, up to 20spores indicate a weak, 20 to 100 a medium and100 and more a severe infestation.

In productive beekeeping, a healthy queen witha good egg-laying capability is always required,and Nosema disease in queens is therefore critical.The queens egg laying ability can be reduced

possibly inducing her supersedure. She may alsobecome the major cause of spreading the diseasewithin the colony. On the other hand, beekeepersare naturally reluctant to destroy queens in theuncertain possibility that they are infected. Themicroscopic inspection of her faeces makes itpossible to verify the presence or absence of thedisease in the queen. Placed alone in aPetri dish,the queen will defecate in about an hour, the faecesappearing as colourless drops of clear liquid. Thisliquid can be examined under the microscope for

the presence of spores, without further preparation(see OIE Manual of Diagnostics, 2004).

ControlNosema can best be controlled by keepingcolonies as strong as possible and removingpossible causes of stress. Colonies and apiariesshould receive adequate ventilation andprotection from the cold and from humidity.The bees should have the possibility of foragingregularly in order to defecate. This preventsspreading of the spores within the colony.

Beekeepers should also ensure that their coloniesand queens come from disease-free stock.

Hive equipment that is suspected of beingcontaminated byNosema apis spores should bethoroughly decontaminated, preferably by heatand fumigation.

The best prevention is to change the combsonce every two years. During normal waxprocessing the Nosema spores are killed.

The only effective chemotherapeutic methodcurrently available for treating Nosema is to

feed the colony with fumagillin (25 mg activeingredient per litre of sugar syrup), preferablyat a time when the colony is likely to encounterstress conditions, such as during a long winter orrainy season. Fumagillin can repress and preventinfection in bee packages, in queens in matingnuclei and in wintering colonies. The activeingredient of fumagillin is an antibiotic. It is ofthe utmost importance that no medication beadministered to colonies when there is a chance ofcontaminating the honey crop.

BOX 2

Heat treatment and fumigation

Heat treatment

Infected equipment is maintained at 49C (120F)

for 24-hours, ensuring that hot air passes through

all stacked combs during the entire period of treat-

ment. The temperature must however be carefully

regulated, because heat at levels higher than that

specified will melt wax.

Fumigation

A pad of cotton or other absorbent material,

soaked with 80 percent acetic acid, is placed overthe top-bars of the comb in each hive. The hive

bodies are stacked together, the entrance is closed,

all cracks are sealed, and the stacks are placed in

an open shed for about a week. After this period,

the hives are opened and the pads of acetic acid are

removed. The combs must then be allowed to air

for 48 hours to rid them of acetic acid residue so

that they can be used again. The spores in the food

cannot be killed. Therefore, the food combs have

to be centrifuged before decontamination. The

food should not be used anymore for bees.


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11

Chapter 3

Parasitic bee mites

Beekeepers throughout Asia generally agreethat parasitic mites are among the most seriousenemies of honey bees with which they haveto cope. In tropical Asia, the success or failureof beekeeping operations withApis melliferadepends largely on mite control.

Several major factors exacerbate bee-miteproblems on the continent. First, all knownmajor species of parasitic honey bee mites arecurrently present in Asia, most being native to thecontinent. Second, the complete eradication of themites from an apiary is impossible, because theferal nests of native bees infested by the parasitesserve as reservoirs of mite re-infestation ofdomesticated honey bee colonies. Moreover, somemite species are able to survive, or even thrive, onmore than a single species of host bee.

Several species of mites have been reported

as causing devastation to bothA.mellifera andA. cerana beekeeping operations throughoutAsia, though not all mite species found withinthe hives or in association with the bees aretrue parasites. Several species of pollen-feedingmites are occasionally found in hives or attachedto foragers. These phoretic mites are mostlyinnocuous to beekeeping. Table 1 contains a list ofparasitic and phoretic mites reportedly found inassociation with honey bees in Asia.

3.1 VARROA MITE (VARROASIS)This mite is a native parasite ofA. ceranathroughout Asia. Since the initiation of beekeepingdevelopment projects withA. mellifera on the

continent, it has been reported as causing damagein both temperate and tropical Asia. The overalleffect of varroa infestation is to weaken the honeybee colonies and thus decrease honey production,often seriously. Occasionally inA. melllfera, andmore frequently inA. cerana, heavy infestation

may cause absconding. Today this parasite is foundthroughout the world, except for Australia andNew Zealand South Island.

In temperate Asia, most beekeepers agree thatvarroa damage is a constraint to the success ofbeekeeping operations withA. mellifera, while intropical Asia success is limited by the loss ofA.cerana colonies through absconding, which is far lessserious and frequent than damage to A. mellifera.Most treatment descriptions are forA. mellifera.Occasional removal ofA. cerana male brood combsand keeping the hive in healthy condition are the

way of prevention of varroosis forA. cerana.

Cause

Varroa destructor(previously confused withVarroa jacobsonii) is quite large, as comparedwith other mite species, and can be seen withthe unaided eye. The shape of the adult femaleis distinctive: observed from above, the widthof the body is clearly seen to be greater than thelength, i.e. about 1.6 x 1.1 mm. The mite is reddishbrown in colour and shiny and the body is dorso-

ventrally flattened covered with short hairs (setae).Adult females ofV. destructorare found insidebrood cells or walking rapidly on comb surfaces.Individual mites are often seen clinging tightly to

TABLE 1

Bee mites and their hosts

Mite Mode of living Host Habitat

Varroa destructor Parasite A. cerana* Brood cell, adult bee

A. mellifera Brood cell, adult bee

Euvarroa sinhai Parasite A. florae* Brood cell, adult bee

Tropilaelaps spp. Parasite A. dorsata* Brood cell, adult bee

A. mellifera Brood cell, adult bee

Acarapis woodi Parasite A. mellifera * Trachea of the adult beeA. cerana Trachea of the adult bee

Neocypholaelaps spp. Phoretic Apis spp. * Adult bee, pollen- storage cell

* Native host of the mite


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the body of adult bees, mostly on the abdomen,where the segments overlap, between the thorax

and the abdomen and at the ventral entry. Adultmales, and the immature stages of both sexes(egg, protonymph and deuteronymph), are notcommonly seen outside the brood cells (seePlate 7). All immature stages of the parasite liveinside the brood cells. They can be observed wheninfested cells are opened and the brood is carefullyremoved. The immature mites are bright whiteand the adult females are brown, while male mitesare smaller than females and are rarely seen sincethey are only found inside brood cells.

SymptomsVarroa causes injuries to honey bees by directfeeding. The adult female pierces the bees softintersegmental membrane with their pointedchelicera and sucks the bees` haemolymph(blood). The adult bee, however, is onlydamaged if the infestation is severe. Varroasis is abrood disease. If more than one parasitic femalemite infests the brood cell the brood decays ordeformations occur including shortened abdomenor deformed wings. If only one mite infests acell symptoms may not be visible, althoughthe bees life-span is considerably shortened.Moreover, the bees behaviour may be disturbed,

e.g. in orientation or gathering food. Infestedbees often have a reduced fat body that hampersthe functioning of their glands or increases theirsusceptibility to pesticides. The semen production

of drones may be considerably reduced.Varroasis is a multi-factorial disease. Virus

diseases that may have caused little damage beforeinfestation by varroa mites often accompanyit. Normally, the exoskeleton protects the beesfrom many virus infections. However, the mitepenetrates this natural barrier transferring virusesor stimulating the multiplication of viruseswith its saliva. In turn viruses seem to speed thedevelopment ofvarroasis enhancing the parasitesvirulence. Other diseases such as nosema and

sacbrood have similar effects.Moreover, unfavourable climatic conditionsor insufficient stocks of pollen and nectar canincrease the process of disintegration. Withouttreatment the colonies normally die after two tothree years, management errors may also causethe collapse of colonies. Colonies destroyed bythe varroa mite are often left with only a handfulof bees and the queen, the other bees having diedduring foraging or having drifted to neighbouringcolonies, where the mite population can increasebefore killing these colonies also. In this way

mites may cause colonies to die, as in some kindof domino effect, over wide areas.

The presence of adult bees with deformedwings, crawling on comb surfaces or near the hiveentrance, usually indicates a late stage of heavymite infestation. Several other methods may beused to detect mites. The most reliable, perhapsthe most time-consuming, is direct sampling bythe random opening of brood cells, particularlydrone cells. The older the larvae/pupae the easierthis procedure becomes. The brood is removed

from the cell with a fine forceps and the cellis inspected for the presence of the mites (seePlate 8). Between 100 and 200 cells must beopened before an assessment of the level of miteinfestation can be made.

To inspect adult bees, the bees are capturedfrom the brood combs and placed in jars, intowhich chloroform, ether or alcohol is introducedon a piece of cotton wool. The bees are intoxicatedand the mites crawl on the glass wall. Returningforagers may also be captured by hand at the hiveentrance and held up against the sunlight; anymites attached to the bees abdomens may be seen.Another method is to use specially constructedzinc, plastic or wood trays, built to the size of

Plate 7Varroa mite showing nymphal stages and male.

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Chapter 3 - Parasitic bee mites 13

with sealed brood for at least two to three weeks.

In this way, mites emerging from the brood willalso be killed. Various applicators have provedeffective for this purpose. A small containerequipped with a wick or paper felt is filled with200 ml of 85 percent formic acid to evaporate forat least 14 days. The quantity to evaporate can beregulated by means of the length of the wick orthe size of the paper felt. The container is eitherplaced on top of the combs, in an empty uppersection or after some combs have been taken out,in the empty space. The external temperatureshould not be less than 12C (54F) and not

BOX 3

Organic acids

Most organic acids are natural components of

honey. In most countries, no fixed maximum resi-

due limits have been fixed for them. Obviously,

overdosing can over acid the honey and change

its taste. Overdosing should also be avoided to

avoid damage to the bees.

Those handling acid must be aware of the risksand wear protective clothing. Formic acid is the

strongest organic acid and can cause extremely

severe skin burns if it comes in contact with the

skin. Skin and eyes must be sufficient protected

while the acid is being prepared and during its

application. In addition, a bucket of water should

be kept close by to serve as a fire extinguisher.

Having to search for water when acid is already

on the clothing or the skin may result in deep

wounds. The same is true for oxalic acid. Here

special precaution is necessary when preparing the

solution with the crystal form. To avoid inhala-

tion, a special mouth protector must be worn.

the bottom board, with a white or light-colouredfloor. The trays, equipped with a screen of a meshless than 2 mm fixed at about 1 cm above the trayfloor, are placed on the bottom boards of the hives

and are inspected one to three days later for thepresence of dead mites. The screen prevents thebees from removing the dead parasites from thehive (see OIE Manual of Diagnostics, 2004).

The control ofV. destructoris one of the mostdifficult tasks facing apiculturists and beekeepersthroughout the world. The mite is a highlysuccessful parasite, whose life history is wellsynchronized with that of its host. Two principalapproaches to its control are currently available:chemical control and hive manipulation techniques,

sometimes referred to as biological control.

Chemical controlChemical control is by far the most popularmethod of varroa control among Asian beekeepersand elsewhere. Although it creates the riskof honey contamination, the accumulation ofresidues within the hive and toxic effects to thebees, beekeepers claim that chemotherapeutictreatment is the quickest and most reliable methodof mite suppression. Among the commonly-usedmite-control agents are organic acids, ethereal oils,

synthetic pyrethroids and amitraz.The application of chemical substances can

only be started after honey harvest, i.e. afterextraction of the honey chamber, respectivelythe honey combs. This is the only way to avoidresidues. A variety of convenient substances areavailable to the beekeeper for varroa mite control.Beekeepers must verify which substance isapproved for use in their countries.

Some preparations have to be excluded becauseof their low effectiveness in colonies with brood.

Among these are Perizin Bayer as well asthe organic acids, lactic acid and oxalic acid.Resistance has developed in certain countries toa few systemic pyrethroids such as fluvalinateand flumethrin, contained in Bayvarol , Apistanand Klartan. Effectiveness must be verified inthe country or region. The organic acids: formicacid, the ethereal oil thymol and the syntheticpyrethroids and amitraz may still be chosen totreat colonies with brood.

Formic acidFormic acid can kill some of the mites in thesealed brood cells. It is recommended that theformic acid be allowed to evaporate in colonies

Plate 8Bee larvae with varroa mites.

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more than 25C (77F). The formic acid shouldbe introduced into the colony only in the lateafternoon to avoid damage to bees and brood. Inaddition, physiological tolerance is improved if

the entrance hole is wide open.An easier way to introduce formic acid is to

use a sponge or a similarly absorbent material. Asolution of 3 ml of 60 percent formic acid is appliedonto the sponge tissue per comb (Langstroh size).The quantity must be reduced accordingly forsmaller comb sizes. A grid fixed above the tissueson the bottom of the hive, will prevent the beesfrom burning themselves with the acid. The gridshould be as far away from the brood as possible.The application can be repeated three to four times

at intervals of at least seven days

Oxalic acidContrary to formic acid oxalic acid does not actvia evaporation but through contact with the bees.Thirty five grams of crystal oxalic acid (dihydrate)is thinned in one litre of sugar water (1:1). Whenhandling crystal acid special precautions mustbe taken because of the health risks. Protectivespectacles and acid-proof gloves must be worktogether with an adequate mouth protector.Depending on the size of the colony 20 to 30 ml

of the suspension per chamber are dropped intothe bee-ways. A repetition of the treatmentcan lead to damage to the bees. Applicators areavailable by which the acid can be evaporated.

Lactic acidLactic acid is clearly better tolerated by beesand does not cause problems in warmer climaticzones. The disadvantage is that every single combmust be extracted to spray the bees with theacid. The dosage applied per comb side is 8 ml of

15 percent acid. This treatment can be repeatedseveral times at intervals of seven days

Etheric oilsThe only etheric oil that is sufficiently affectiveagainst varroa mites is thymol.

ThymolThymol can be applied as a commercially availableready-made preparation or in crystal form. Forthis purpose, 0.5 mg thymol per bee-way are putinto a gauze bag and deposited onto the combs forsome weeks. In this way mites emerging from thebrood will be covered.

Synthetic chemicals

PyrethroidsSynthetic pyrethroids are contained in Apistanand Bayvarol, which have been developed forapplication to bees. The plastic strips are fixedin bee-ways in the brood nest. When the beescome into contact with them they transportthe substance to the other bees, thus killingthe parasitic mites on the bees. As the stripsremain for several weeks in the colony mitesemerging from the brood are affected. Syntheticpyrethroids are highly effective, although there is

the disadvantage that mites may rapidly developresistance to them. Therefore, their effectivenessshould be controlled regularly. Syntheticpyrethroids are also available in formulations notspecifically intended for use on bees.

AmitrazTaktic and Mitac are trade names of productscontaining amitraz at different concentrations.The recommended dosage for use on honeybee colonies is 1 ml of 12.5 percent amitraz to

10 litres of water, sprayed lightly on bees, thecomb surface of brood frames and hive walls.The amount of the solution to be sprayed at eachapplication depends on the size of the colony, butis usually within the range of 80 to 250 ml.

Amitraz can also be used as a hive fumigant.Strips of filter paper 2.5 x 9 cm are soaked in a

Note that amitraz can kill bees. A major disadvantage

of amitraz is that it has an ovicidal effect: when used

as a hive spray it will kill eggs. It must therefore not

be sprayed directly on frames containing a considerable

number of eggs or newly-hatched larvae.

Plate 9Adult female of Tropilaelaps spp.

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saturated solution of potassium or sodium nitrateand allowed to dry, then 0.1 ml of the product isapplied onto each paper strip. Fumigation shouldtake place in the evening, when the foragers have

returned to the hive. The technique is simple:an impregnated strip of paper is fastened to anempty frame, lit and allowed to smoulder fromthe bottom end upward. The frame is insertedinto the hive, supported by an empty super placedabove the brood chamber. The hive entrance isclosed, and all cracks are sealed with maskingtape. The entrance can be reopened after 20 to 30minutes. If sealed brood is abundantly presentin the infested colony, the treatment must berepeated two to three times at four-day intervals.

Control by hive manipulationThe varroa mite depends on bee brood tocomplete its development cycle. Since the miteprefers drone brood to worker brood, emptyframes are given to the colonies, which will reardrone brood in them. When the cells are sealed,the frames, containing the mites trapped inside thecells, can be removed and destroyed.

The mites can also be trapped in worker-broodframes by using vertical queen-excluders in single-storey hives. The queen is confined between two

excluders and allowed to lay eggs in one frameonly. Female mites in the colony will be attracted tothis brood frame which, when the cells are sealed,is removed from the colony so that the brood cellsinfested by the parasites can be destroyed

3.2 TROPILAELAPS MITEModern beekeeping withApis mellifera intropical and sub-tropical Asia frequentlyencounters problems caused by infestation withTropilaelaps spp. The mite is a native parasite

of the giant honey beeA. dorsata, widelydistributed throughout tropical Asia, andwheneverA. mellifera is kept within the range ofdistribution ofA.dorsata, mite infestation of thecolonies cannot be avoided. Thus, in Thailandbeekeepers consider Tropilaelaps to be a moreserious pest than varroa-mites, even thoughit may be easier to control. Dual parasitismofA. mellifera colonies by both parasitessometimes occurs, the population ofTropilaelapsoften being greater than that of varroa, as theTropilaelaps mite can almost completely preventmultiplication of the varroa mite.

CauseTropilaelaps mites are much smaller than varroamites, although the trained unaided eye can stillsee them. The adult female mite (see Plate 9) is

light reddish-brown in colour, with an oval-shapedbody about 0.96 mm in length and 0.55 mm inwidth. The mites entire body is covered withshort setae. A red streak running longitudinally onthe ventral surface of the adult female, the fusionof her epigynial and anal shields may be perceivedthrough a strong magnifying glass.

When the mites are present in a honey beecolony in large numbers, they can be observedwalking rapidly on the surface of the comb. Theyare rarely found on adult bees.

In all its immature stages, the mite lives withinthe brood cells of the bees, feeding on the broodshaemolymph (Plate 10). Fertilized adult femalesenter the cells before they are capped to lay theireggs. The stages of development of the mite areas follows: egg, six-legged larva, protonymph,deutonymph, adult. Adult males ofTropilaelapsdo not feed, their chelicerae (the organs originallyused for piercing the bees integument) havingbeen modified to transfer sperm as with thevarroa mite. The life cycle of the mite is wellsynchronized with that of the host bee.

SymptomsThe damage caused to colonies by Tropilaelapsinfestation is similar to that brought about byvarroa and the injuries inflicted on individualbees and bee brood are essentially the same. Theabdomen of bees surviving mite attacks is reducedin size, and they have a shorter life-span thanhealthy bees (see Plate 11). In heavily infestedcolonies, bees with deformed wings can beobserved crawling about the vicinity of the hive

entrance and on the comb surfaces, while pieces

Plate 10Adult female of Tropilaelaps spp. on A. mellifera pupa.

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of dead bee brood evacuated from the hive by thehouse bees can be seen in front of the entrance.

Inspection of hives severely infested byTropilaelaps reveals an irregular pattern of sealed

and unsealed brood as found with all brooddiseases. Since this symptom can be taken as asign of a poor-laying queen, the position mustbe verified. The best means is to open sealedcells gently and inspect them for the presenceof the mite. If mites are present, adult femaleswill be seen walking rapidly out of the cells. Toobtain a reasonably accurate estimate of the levelof infestation, 100--200 cells should be openedand the brood removed with forceps for closeinspection (see OIE Manual of Diagnostics, 2004).

ControlPreventing infestation by the Tropilaelaps miteis nearly impossible. It has been discussed if thevicinity ofApis dorsana colonies might contributeto the transfer of the mite. As is applicable toother bee diseases, robbery or a too large beedensity should be avoided.

Since it is almost impossible to avoidTropilaelaps infestation ofA. mellifera colonieskept commercially on the tropical and sub-tropical Asian mainland, the key question is

how to cope with the problem. In recent years,apiculturists and beekeepers have learned how topartly solve it. Owing to the fact that the adultfemale of the mite can survive without bee broodas food for only up to seven days, its control issomewhat less complicated than that ofvarroa,although this should not be taken as meaning thatTropilaelaps is not a serious pest.

Chemical controlThe chemotherapeutic measures described abovefor the control ofvarroa are also effective inthe control ofTropilaelaps. Not all preparations

used for varroa control have been tested onthe Tropilaelaps mite. Formic acid can be usedsuccessfully in its treatment. However, specialattention must be paid in tropical areas regardingits dosage to avoid damage to the bees. Thedosage per comb should not exceed 2 ml in a one-storey Langstroth-hive.

The formic acid is placed onto a clothdeposited in the rear section of the hive. Formicacid is strongly caustic; therefore, the user shouldwear acid-proof gloves and protective goggles.

Applications of amitraz are very effective either asa liquid spray on the surface of the brood comband hive walls, or as a hive fumigant, in the samedosages. The treatment requires three to fourapplications at four-day intervals. The precautionsto be taken in treating Tropilaelaps are the sameas for varroa; all chemical treatments must besuspended at least eight weeks before the honey-flow season arrives, and amitraz must not be usedin spray form in the presence of large numbers ofhoney bee eggs and newly-hatched larvae.

Colony manipulation techniquesMany beekeepers prefer not to use chemicals tocontrol Tropilaelaps, but to manipulate the brood-rearing cycle of their infested colonies in sucha way that the mites are deprived of sealed andunsealed brood, their food, for at least three days.During this period, a large proportion of the mitepopulation will starve to death.

There are several means of creating this brood-less situation in infested colonies. In smallerapiaries, the beekeeper can simply remove the

brood-comb frames -- both sealed and unsealed-- from the infested colonies and put them innew hives. Before the new larvae hatch, the hivesmanipulated in this way will be short of broodfor two to three days, time enough to starve mostof the mites. The new hives with the removedbrood frames are given mated queens, which arecaged for 14 days, a period that allows most of thebrood to emerge, while no new brood has beenreared because the queen has been confined.

When the drone population in the coloniesis high, and the beekeeper wishes to increasethe number of colonies, the new ones may begiven newly-reared, capped queen cells insteadof mated queens. By the time the virgin queens

Plate 11Parasitism by Varroa jacobsonii or Tropilaelaps clareaeusually results in deformation of the bees wings.

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emerge, mature, mate and are ready to lay, mostof the brood will have emerged; the rest can bedestroyed before egg-laying begins. There willthus be sufficient time to starve most of the mite

population in the colonies.The best time of year to carry out these

colony-manipulation techniques is during a heavypollen-flow season, enabling the colonies to rearbrood after the period of brood deprivation. Insome Asian regions, this season coincides withthe monsoon months, when there is no nectarflow but when pollen is abundant. This is alsothe season in which beekeepers feed sugar syrupto their bees, rear new queens and propagatecolonies. While colony manipulation to control

Tropilaelaps is time-consuming, it causes nonoticeable harm to the colonies, nor does it affectproductivity. The availability of pollen, coupledwith the feeding of sugar, enables both the treatedand the newly-formed colonies to regain their fullstrength before the nectar flow begins.

Some beekeepers prefer to combine chemicaltreatment with the brood-deprivation technique. Inthis approach, all sealed brood is removed from themite-infested colonies, which are then fumigated.The adult female mites, having no capped broodcells in which to hide, are for the most part

killed by the fumigant, so that only one chemicaltreatment is required instead of three or four.Recent examinations have shown that, in specialcases, the Tropilaelaps mite can survive longer thanseven days without bee brood. Despite this, thesebio-technical methods have the advantage that thenumber of mites in the bee colonies is drasticallyreduced and damage is avoided.

3.3 TRACHEAL MITE (ACARAPIDOSIS)This mite,Acarapis woodi, infests the tracheal

system of adult bees, queens, workers and drones,which are all equally susceptible to its attacks. Sinceit was first reported inApis mellifera colonies inEurope in 1921, opinions regarding the extent ofthe damage it can cause to honey bee colonies havevaried. Reports from India and Pakistan indicatethat the tracheal mite caused severe losses ofA.cerana colonies. However, the mites range ofdistribution in Asia has not been firmly established,and many of the reported losses ofA. ceranawere later shown to have been inflicted byApisiridescent virus and not by tracheal mites. Afterthe first appearance of theAcarapis mite in NorthAmerica it has led to increasing damage; therefore,beekeepers in Asia should remain vigilant.

CauseA. woodi is a very small mite (0.1 m) species thatlives and breeds within the thoracic tracheae ofadult bees (see Plate 12). The mite penetratesthrough the stigma (spiracles) into the first tracheapair of the thorax of 10-day old honey bees. Thereit lays eggs at intervals of a few days. After thedeutonymph stage, male offspring emerge afteraround 12 days and females after 13 to 16 days.

SymptomsUnfortunately, there are no reliable typical visible

symptoms of infestation. Indeed, it has beendemonstrated that bees severely infested withthe mite can forage normally. Nevertheless, somedifferences exist with regard to the over-winteringcapability of infested and healthy colonies.Infestation shortens the lifespan of the individualbees, so that severe infestation of colonies causesthem to lose strength and thus increases a colonyssusceptibility to winter losses.

The most reliable diagnostic method islaboratory dissection. Samples of 20 or more bees

found crawling near the hive and unable to flyare killed, their heads and legs removed and theirthoraxes dissected for microscopic examination.If present, the mites are usually found at the endof the first pair of trachea in the thorax (see OIEManual of Diagnostics, 2004).

ControlChemotherapeutic measures are widely adoptedfor mite control. Best results could be achievedwith evaporating substances such as formic acidand ethereal oils.

Plate 12Tracheal mite, Acarapis woodi.

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Formic acidFormic acid produces good results by applyingit onto a cloth (20 ml of 65 percent formic acid)four times at intervals of seven days. The user

must use special protection: acid-proof glovesand protective goggles. Treatment should beconducted during a period of low humidity andthe temperature should not exceed 30C (86F).

Menthol or thymolMenthol has a toxic effect onA.woodi in beecolonies. Crystalline menthol (50 g) or thymol(15 g) is placed in a gauze bag on the top of thebars to be kept there for one to two months.External temperatures should be around 21C

(70F); otherwise the menthol vapours will notreach the mites in the trachea.


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19

Chapter 4

Insects

4.1 BEETLEThere are several different beetles living inhoney bee colonies. Most are harmless and feedon pollen or honey.

Small hive beetle (SHB)

Originally, this beetle (Aethina tumida), wasonly found in Africa, south of the Sahara. Itfirst appeared in the southern United States ofAmerica in 1998 and has continued to spreadnorth as far as Canada. Since 2002 this beetle hasbeen found in parts of Australia.

In Africa, the beetles original range, only weakcolonies or storage combs are affected. However,in America or Australia, colonies of ordinarystrength can be affected. The main reason for thisseems to be the different defence behaviour of theimported European bees. On the other hand, the

beetle also invades a colony during managementactivities, e.g. during honey extraction. There is arisk that the beetle may spread to Asia.

CauseThe beetleAethina tumida (order: Coleoptera,family:Nitidulidae) is called the small hive beetle(see Plate 13). This beetle lives and multiplieswithin and outside bee colonies. The beetledeposits larger deposits of nests of eggs within abee colony, in fissures and recesses out of reach

of the bees. The larvae of this beetle preferably

live on and in pollen and honeycombs. The adultlarvae leave the hive to pupate in the earth in frontof the apiary. The period of development from eggto adult beetle is at least four to five weeks.

SymptomsThe beetles and their larvae can infest bee broodand honeycombs in and outside the apiary. Therethey form eating canals and destroy the cell caps,and the honey starts to ferment. The beetles larvae

and faeces also change the colour and taste of thehoney and the combs appear mucilaginous.

The adult beetle is dark brown to black,around 5 mm long and 3 mm wide. Whereasthe beetle may be found throughout the beehive, the white larvae, around 11 mm longare mainly found in the combs (see Plate 14).They can easily be distinguished from the waxmoths that may also be living in the bee colonybecause their legs are longer and they have arow of spines on their back and do not spin

nets or cocoons. A minor infestation is difficultto recognize because the beetles immediatelyhide in the dark. The most secure diagnosis isachieved after chemical treatment when the deadbeetles can be gathered from the bottom inlay(see OIE Manual of Diagnostics, 2004).

ControlThe best way to protect against an infestation ofthe small hive beetle is to keep strong colonies andto remove those that are weak from an apiary. Theremoved honey combs should be centrifugallyextracted one to two days after harvesting thehoney. These can be stored at less than 10C orin a dry environment having less than 50 percent

Plate 13Small hive beetle.

C

VUAFREIBURG

Plate 14

Small hive beetle larvae.

CVUAFREIBURG


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relative air humidity, which may prove toocomplicated for the individual beekeeper.

Currently, a successful control is made possibleusing a preparation named Checkmate, produced

by Bayer (a.i. Cournaphos). This product hasprovisional market approval in some statesof the United States. More than 90 percent ofadult beetles and larvae may be killed with thispreparation. Other chemical treatments are underdevelopment. However, the problem is that thisbeetle contrary to the varroa mite can liveand multiply outside the bee hive, where it seemsto prefer rotting fruits (e.g. apples and bananas)as nesting sites. This is why reinvasion is alwayspossible. The beetle is extremely quick moving

and can fly, which contributes to its rapid spreadamong bee colonies and apiaries.

4.2 ANTSAnts are among the most common predatorsof honey bees in tropical and subtropical Asia.They are highly social insects and will attackthe hives en masse, taking virtually everythingin them: dead or alive adult bees, the broodand honey. In addition to this destruction, theycan also be a nuisance to beekeepers and maysometimes cause pain from their bites.

Apiaries ofApis mellifera under ant attackbecome aggressive and difficult to manage; weakcolonies will sometimes abscond, which is also thedefence ofA. cerana against frequent ant invasions.

Many ant genera and species are reported to causeproblems to both traditional beekeeping withA.cerana and to modern beekeeping withA. mellifera.Among the most frequently recorded species arethe weaver ant (Oecophylla smaragdina), the blackant (Monomorium indicum), Monomorium destructorand spp., Oligomyrmex spp.,Dorylus spp., the fire

ants (Solenopsis spp.) andFormica spp.

ControlBeekeepers have found that the most effectivemethod of controlling weaver ants is to searchsystematically for the ants nests in the vicinity of

the apiaries and, when found, to destroy them byburning. General recommendations to reduce antnesting sites include eliminating brush and rottenwood from the apiary and cutting the grass.

A good general defence against ants in tropicalapiaries is to place the hives on stands supportedby posts 30-50 cm high and to coat the posts withused engine oil or grease. Frequent inspection andrenewed application of grease are both necessary anda source of soil pollution. A more reliable methodis to place the hive-stand posts in tin or plastic

containers filled with either water or oil. Regularclean up is required to avoid the formation of bridgesof vegetation or earth that can be crossed by ants andliquids need to be replenished frequently.

4.3 WASPS AND HORNETSNearly all countries in Asia report wasps andhornets as common enemies of their honey bees.Among the most frequently reported are socialwasps of the genus Vespa, which are widelydistributed throughout the world. Colonies of bothA. cerana andA.mellifera are frequently attacked.

Hornet invasion ofA. cerana colonies generallycauses the bees to abscond, and similar behaviour isreported of weak colonies ofA. mellifera.

In addition to hornets of the genus Vespa,other wasp species have occasionally beenreported to cause damage to apiaries. Among theseare several species of the genus Vespula, which aredistributed throughout temperate Asia.

Table 2 lists wasps and hornets that havebeen reported as major predators of the twohoney bee species in Asia.

Predation by Vespa spp. on commercial apiariesis generally a seasonal problem. In Japan, and

TABLE 2

Wasps and hornets that attack bees in Asia

Scientific name Recorded distribution

Vespa orientalis India, Pakistan

Vespa mandarina India, Burma, Thailand, Lao, Viet Nam, Democratic Kampuchea,China, Republic of Korea, Japan

Vespa tropica Tropical Asia

Vespa velutina Tropical Asia

Vespa cincta Tropical Asia

Vespa affinis Tropical and sub-tropical Asia

Vespa crabro Japan, and perhaps all temperate AsiaVespa mongolica Japan, and perhaps all temperate Asia

Vespula lewisii Japan

Vespula vulgaris Republic of Korea


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Chapter 4 - Insects 21

probably in the rest of temperate Asia, hornetattacks on apiaries reach their peak of intensityduring September-October, whereas in tropicalcountries the most serious wasp invasions take

place during the monsoon season, particularlyfrom late June to August. Apiaries situated nearthe foothills and tropical forests suffer moreacutely than those on the plains.

Studies of the predation of honey bees byVespa mandarina in Japan and by V. affinis inThailand appear to indicate that the attackingbehaviour of the larger wasps, and perhaps allspecies ofVespa, is similar. Initially, a huntingphase is observed, during which a few hornetscapture and kill slow-flying bees one at a time,

usually near the entrance of a weak colonys hive.Later, a slaughtering phase sets in: some 20 to30 hornets attack a weak colony en masse, usingtheir strong jaws to maul the bees and droppingthe dead and dying bees to the ground. Finally,when this phase has continued long enough forthe colony under attack to have lost most of itsdefender workers, the hornets invade the hiveitself, the honey and brood nest and the waspscarry away any surplus brood to their nest.

Control

Thanks to their reasonably large body size (seePlates 15 and 16) the foraging range ofVespa canbe a comparatively large area around their nests,which may have populations of many thousands ofindividuals. Beekeepers in Japan sometimes adoptmethods such as bait-trapping, trapping at the hiveentrance and using protective screens. Locatinghornet nests by following flight passes of individualwasps back to their nests and then destroying thenests may be very time consuming and, if too manyof these nests are in the area, not very efficient.

Where labour costs are not prohibitive,beekeepers have resorted to capturing and killingindividual hornets foraging in the vicinity of theirapiaries. In Thailand, this approach has proved tobe quite effective, largely because the period ofmost intense hornet attacks is only two to threemonths. It has been seen that the real damageinflicted by hornet attacks on honey bee coloniesoccurs during the slaughter and occupationphases. Killing hornets in the early stage ofpredation has the effect of disrupting the huntingphase and preventing the predation processfrom reaching the more destructive phases. Massdestruction of the colonies is thus prevented or, atthe least, minimized.

As a final, and more general, recommendation

for protective action against hornet attacks whenthe hives cannot be relocated to a safer place,beekeepers should as a minimum preventivemeasure narrow the hive entrance. In this way, thefinal invasion of the hive can generally be avoided.

4.4 WAX MOTHS AND OTHER LEPIDOPTERA

The greater wax moth (Galleria mellonella)The greater wax moth is often reported to causedamage both to honey bee colonies and to bee

products in tropical and sub-tropical Asia. Emptycombs, rendered wax, comb foundation and bee-collected pollen, if not properly stored and leftunattended, almost always suffer considerabledamage from wax-moth infestation (see Plate 17).According to many reports, the wax moth is a majorpest ofA. cerana, often causing colonies to abscond.

In wax-moth attacks on colonies, the adultfemale enters the hive at night, through theentrance or cracks in the walls, deposits her eggsdirectly onto the combs or in narrow crevices thatpermit oviposition and offers protection againstremoval by worker bees. From 50 to 150 eggs arelaid in each batch; they are glued together andadhere firmly to the surface on which they are

Plate 15Apis mellifera colony invaded by Vespa tropica.

Plate 16Comparative body sizes of (left) Vespa tropica and (right,top to bottom) Apis florea, A. cerana and A. dorsata.


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laid. The newly-hatched Galleria larvae feed onhoney and pollen, and then burrow into pollen-storage cells or the outer edge of cell walls, laterextending their tunnels to the midrib of the combas they grow. At this stage the developing larvaeare quite safe from the worker bees. As theyadvance into the combs, they leave behind them amass of webs and debris; the complete destructionof unattended combs usually ensues within 10-15days. In addition to stored pollen and comb wax,larvae of the greater wax moth will also attack bee

brood when short of food.The development time ofGalleria larvaedepends on two factors: food availability andtemperature. Whereas in tropical climates thelarvae require only 18-20 days before spinningcocoons and becoming pupae, in cooler climatesthis period may be extended.

When weak colonies are infested, the symptomof galleriasis is frequently observed: theemerging adult worker and drone bees are unableto leave their cells because their bodies have beentied up by silken threads spun by the Gallerialarvae.

Plate 17Best prevention of wax moths: keeping the apiary clean.

W.RITTER

ControlThere are no easy or inexpensivechemotherapeutic measures for controlling thewax moth in living honey bee colonies once

infestation has set in. The only possibility istreatment with Bacillus thuringiensis, in a waterysuspension, sprayed onto the combs. The effect onthe wax-moths larvae persists for several weeks.

Preventive measures include ensuring that thecolonies, whether ofA. cerana orA. mellifera, arestrong and have adequate food stores; adaptingthe hive space to the strength of the colony;reducing the hive entrance; sealing cracks andcrevices in hive walls; protecting the coloniesagainst pesticide poisoning; controlling pests and

diseases that might otherwise weaken them; andremoving any wax and debris accumulated on thebottom boards of the hives.

Several measures can be taken to prevent orcontrol wax-moth infestation in stored combs andhive products. Products that are vulnerable to waxmoth attack such as empty combs, used hive partsand wax should be properly stored, preferably intight, moth-proof rooms. As preferably formerlyhedged combsare infested they should be storedapart from new ones.

Fumigation is the usual treatment; new combs

should be treated less frequently. Among themost commonly used fumigants are naphthalene,ethylene dibromide and methyl bromide. All,including paradichlorbenzene, are very poisonousto bees and humans and, in addition, lead toresidues in honey. The application of sulphur,however, is inoffensive. Sulphur powder iswrapped in newspaper and burned in a metalcontainer. Liquid sulphur from sprayers can alsobe used. The development of wax moths canbe interrupted for several months if the combs

are heated at 48C (118F) for three hours.All treatments should be repeated at intervalsdepending on the level of infestation. Regularcontrol is therefore recommended.

The lesser wax moth (Achroia grisella)As its name implies, the lesser wax moth isgenerally smaller than the greater wax moth,except when the latter is dwarfed owing to poordiet during its larval stage. AdultAchroia grisellaare silver-grey in colour, with a distinct yellowhead. The insect is quite small, with a slenderbody: normal body lengths of adult female andmale are about 13 and 10 mm respectively. Thelife-span of the adult female is about seven days,


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Chapter 4 - Insects 23

during which she can lay 250 to 300 eggs.Infestation by the lesser wax moth usuallyoccurs in weak honey bee colonies. The larvaeprefer to feed on dark comb, with pollen orbrood cells. They are often found on the bottomboard among the wax debris. As larvae prefer toform small canals between the bottoms of thebrood cells the brood is lifted. The bees continueconstructing cells heading upward leading to thetypical scratched comb surface (see Plate 18).

Control

The methods employed in controlling Galleriamellonella are equally effective for the control ofAchroia grisella.

Other LepidopteraOther moth species are frequently recorded inassociation with bees and bee products. TheIndian meal moth Plodia interpunctella is reportedto feed on bee-collected pollen. Moths found deadon the bottom boards of beehives include deaths-head or hawk moths (Acherontia atropos), which

invade the hives to feed on honey. Beekeepersgenerally consider them to be minor pests.

Plate 18Brood surface (open cells with immature pupae)changed by wax moth.

CVUAFREIBURG


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25

Chapter 5

Vertebrates

5.1 AMPHIBIANSBeekeeping in tropical climates frequentlysuffers from damage caused by amphibians:toads including Bufo melanostictus andKaloulapulchra and frogs including Rana limnocharisand Rana tigrina. The detection of this problem

generally requires close observation: beekeepersare normally unable to observe intense predationby amphibians on honey bees in the daytime,when they are at work in their apiaries, becausethe heaviest attacks occur at night. Often theproblem goes unrecognized until a substantial fallin colony populations is perceived.

One sign indicating that toads and frogs arepreying heavily on the colonies is the presence ofthe predators dark brown droppings, scatteredin front of the hive entrance. If the dry faecaldeposits are spread apart (e.g. with a twig), the

remains of bee parts can be seen.Continuous predation by toads and frogs, if

not prevented, results in a loss of colony strength.While colonies with moderate or larger workerpopulations can withstand the predation and

subsequently recover their full strength, weakercolonies are at considerable risk.

Toads and frogs have similar attacking patterns.On arriving at the colony, the amphibians waitin the vicinity of the hive entrance, preying onpassing bees (see Figure 1). Colonies close to the

ground provide easy access to the predators, forwhich guard bees at the hive entrance are easyprey. If the attackers are small enough to squeezethrough the hive entrance of a weak colony, theoutcome can be devastating.

ControlAlthough in some circumstances predation onhoney bee colonies by amphibians cannot beoverlooked most beekeepers perceive the problemas minor. Placing the hives on stands 40 to 60 cmhigh is usually a sufficient protective measure.

Where large numbers of the predators tend tocongregate near an apiary, it may be necessaryto fence it with fine-mesh chicken wire. Othermethods such as trapping, baiting or poisoninghave not been advocated.

5.2 REPTILESGeckos, skinks and other lizards are among themost commonly found reptiles in tropical Asian

jungles, woods, grasslands and urban areas.Among the reptile species that are regularly

recorded as present in commercial apiaries are thetokay (Gecko gecko), which can be as much as35 cm long, Calotes spp., Acanthosaura spp. andthe skink Sphenomorphus spp.

Arboreal reptiles such as many geckos andskinks can attack bees either near the hiveentrance or on the limbs of flowering trees visitedby forager bees. Smaller lizards, such as the geckoHemidactylus frenatus, often hide in the emptyspace between the outer and inner covers of thehive (see Figure 2). In tropical areas, this type ofpredator frequently causes the sudden loss of thequeen from a weak colony.

FIGURE 1

Predation by toads on a honey bee colony


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ControlThe beekeeper can do little to prevent the loss offoragers to the highly mobile arboreal reptiles,usually well hidden in the trees. Beekeeperscan destroy as many of them as possible whenthey are encountered, though this method is notrecommended nor is it efficient. Hives placed onstands that are about 40-60 cm high are reasonablysafe from reptiles attacking from the ground;coating the legs of the stands with used engine oilor grease may deter the reptiles from climbing upto the hive entrance. A well-kept bee yard that is

frequently mowed, without dense bushes, shrubsand tall grass, that provide safe hiding places to thepredators, has less chance of suffering losses fromreptiles than an untended one. No reliable chemicalcontrol of reptiles is available for use in apiaries.

5.3 BIRDSBirds prey upon many insect species and honeybees are no exception. Once airborne, the beesare virtually defenceless against birds, severalspecies of which can tolerate their venomous

stinging defence. The heavy traffic of beesflying in and out of the hives of commercialapiaries provides an exceptional opportunity forinsectivorous birds, large numbers of which maybe attracted by this situation.

Birds that have been listed as attacking honeybees in Asia include bee-eaters (Merops apiaster,Merops orientalis), swifts (Cypselus spp., Apusspp.), drongos (Dicurus spp.) shrikes (Laniusspp.), woodpeckers (Picus spp.) and honeyguides (Indicatoridae).

The level of damage caused by apivorous birdsvaries. An attack by a single bird or by a fewtogether rarely constitutes a serious problem,but when a large flock descends upon a few

colonies or an apiary, a substantial decline in theworker population in some or all the hives maybe observed. Whereas the degree of damage tocommercial apiaries caused by predatory birds

depends largely on the number of the predatorsand the intensity of the attack, the mere presenceof a few predators in apiaries engaged in queen-rearing can inflict serious losses.

ControlWhile beekeepers regard insectivorous birdsas pests, sometimes serious, other branches ofagriculture generally do not consider them asproblematic. In fact, birds that prey on insects aremostly considered to be beneficial to farming, in

that they help in the control of insect pests. Forthis reason, before any attempt is made to solvethe apiarys bird problems by mass killing of thepredators, whether by chemical or physical meansor by gunshot, the implications of this action on theenvironment must be seriously taken into account.

Where heavy predation by birds on apiarybees tends to occur at fixed periods (e.g. duringthe migration season of swifts), the most practicalmeans of solving the problem is usually to avoidthe birds, through careful site selection and bytemporary relocation of the apiaries, at least until

the migration period is over.

5.4 MAMMALSMany groups of mammals may be considered asenemies of the honey bee. In general, they prey oncolonies for honey and/or brood; some attacks arepurely accidental or the result of animal curiosity.Such cases usually occur

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