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ForestAwareness

A|Oint reportof the Canadian Pulpand Paper Association and the Forest Pest Management Institute

technical reference

insecticide

BACILLUS THURINGIEIMSISvar. KURSTAKI

• BASIC FACTS

1. Common Name:

2.

B.t.k. (Bacillus thuringiensisvar. kurstakil

Biological Classification:

A rod-shaped spore-forming bacterium Bacillusthuringiensis var. kurstaki

3. Active ingredient:

At sporulation B.t. cells produce spores and proteincrystals. These crystals have a bipyramidal shape (seephoto) and are 1-2 microns in length. In the alkalineenvironment of the insect gut, the crystal dissolves intoprotein subunits. which are then attacked by digestiveenzymes and converted to toxic protein molecules. Threecommercial varieties of B.t. exist, each being specificallypathogenic for limited insect groups. B.t. var. kurstaki isspecific to lepidopterous insects. Other varieties are B.t.var. israeliensis [B.Li.) active against mosquitos andblackflies, and B.t. var. tenebrionis (B.t.t.) effective againstColeoptera.

4. Commercial Forestry Products:

Nine formulations based on Bacillus thuringiensis var.kurstaki'strain HD-1 are presently registered for use inforestry including:

Name Manufacturer Reg. No Guarantee?(PCPAP

RegisteredUse'

Dipel 48AF Abbott Laboratories, Ltd. 20861 12.7 BIU/L For & WId

Dipel 64AF

Dipel 132

Abbott Laboratcies,

Abbott Laboratories

1 id

Ltd.

21526 16.9 BIU/L

17954 12 7 BIU/L

for & WIdFor & WId

Dipel 176 Abbott Laboratories Ltd 20599 16.9 BIU/I For & WId

Dipel 264 Abbott Laboratones, Ltd 23044 25.3 BIU/L For & WId

Foray 48B Novo Nordisk

Biolndustrials, Inc. 21464 12.7 BIU/L For & WId

Fcray 76B Novo Nordisk

Biomdustrials, Inc. 22403 20.0 BIU/L For & WId

Futura XLV-HP Novc Nordisk

Biomdustrials, Inc. 21484 33.0 BIU/L For & WId

Thuncide 48LVSandoz Agro Caradc , Inc 17980 12 7 BIU/L -::• .-. .', :

II PCPA: Pest Control Product Act

2) Guarantee is evaluated in terms of potency which is measured in BillionInternational Units per volume or weight, reflecting the biological activity of theformulation against larvae of the cabbage looper. Tnchoplusta ni. in astandardized bio-assay

3) For=Fo'ests; Wld=Woodlands.

5. Physical and Chemical Properties:

Commercial B.t. products consist of a mixture of sporesand crystals formulated as flowable aqueous liquidconcentrates or oil-based emulsifiable suspensions.Physical and chemical properties vary with eachformulation. Furtner specific information concerning theseaspects can be obtained from the manufacturers.

6. History:

B.: was first discovered as an insect pathogen in 1911.Canada, the first operational aerial applications againstforest insects were carried out in the 1960's with B.t.k.The use of B.t.k. has increased dramatically since the1980s (Morris etal., 1986), due to improvement in

formulation and application technology and also because ofenvironmental concerns. While effective against severalforest defoliators, its mam application at present is thecontrol of the spruce budworm. In most provinces, B.t.k. isthe only product used for spruce budworm control.

7. Herbicide Spectrum and Mode of Action:

B.t. var. kurstaki'strain HD-1 is toxic specifically to larvaeof lepidoptera including many species that are forestryand agricultural pests. B.t.k. is a stomach poison and hasno contact action. After ingestion of a lethal dose, thetoxin destroys the midgut walls and the larvae stopfeeding within hours. Death usually follows within 2 to 5days.

• REGISTERED USES AND

APPLICATION TECHNOLOGY

1. Registered Uses For Forestry:

2.

B.t.k. products are registered for forest management use(>500ha) and woodlands management use (s=500ha) andmay be applied using ground or aerial equipment. Allforestry uses are restricted; consult local pesticideregulatory authorities about use permits which may berequired.

The various B.t.k. products are registered for the controlof a variety of defoliating species of Lepidoptera. Pestscontrolled include eastern and western spruce budworm,jackpine budworm, gypsy moth, eastern hemlock looper,forest tent caterpillar, spring and fall cankerworm, elmspanworm, bagworm, and fall webworm. Product labelsshould be consulted for product specific uses. Dependingon registration, the products can be used in forests,woodlands, woodlots, nurseries and Christmas treeplantations by aerial application or ground spraying. Avariety of dosages are recommended, depending onpurposes and products. They vary from 20 to 50 BlU's/ha,in single or multiple applications. Formulations withrestricted registration for forestry are emulsifiablesuspensions (oil-based) or suspension concentrates(water-based). They range in concentration from 12.7 to33 BIU/L.

Operational Details:

• Usage ratesPotential users are referred to product labels,local/provincial laws and regulations, federal and provincialforestry regulatory officials as well as manufacturer's staffand literature, for details necessary to plan specificprojects.

In forestry applications best results are obtained by aerialapplication of undiluted product in low spray volumes.Volume application rates will depend on productconcentration, dosage applied, type of equipment andtarget pest. When spraying undiluted at 30 BlU/ha sprayvolumes range from 0.9 to 2.4 L/ha (using 12.7-33 BIU/L).At such low spray volumes, rotary atomizers capable ofproducing a droplet spectrum between 30 and 80 micronsshould be used to obtain adequate coverage.

• Target and timingSince B.t.k. is a stomach poison, the direct targets forapplication are the foliage, the buds or the flowers that thelarvae are feeding on. For best impingement of spraydroplets, application should be carried out only whenenough foliage is available and larvae are feeding actively,but before extensive feeding damage has occurred. Thetiming of the applications will depend on the stage ofdevelopment of the insect and the bud or foliagedevelopment. Timing is thus a compromise between hosttree phenology (bud flush) and target insect phenology(instar development).

Target

spruce budworm

lackpine budworm

hemlock looper

gypsy moth

other forest insects

Timing

Soon after bud flush, before 6,h instar.If population density is high, repeat after 3 to 5 days

Soon after needle pairs start escaping from sheath

Soon after onset of egg hatch, between 1='and 3rainstar. Repeat application after 7-14 days will benecessary due to extended egg hatch

When leaf expansion reaches 40-50%, before3"1instar. If egg hatch is prolonged (cool spring),repeated applications within a 5-10 days intervalis recommended.

Generally as soon as larvae feed openly onflushed foliage.

• MixingAlthough all B.t.k. formulations come in a ready-to-sprayundiluted form, it is possible to dilute formulations withwater to increase the volume of the spray. As a rule thelowest dilution rate possible consistent with thorough,well distributed, adequate coverage is preferred. Do notallow diluted spray mixtures to stand in the spray tank fora prolonged period. Follow label directions. Oil-basedproducts should not be mixed in a ratio of less than 60parts of water to 40 parts of product.

• EFFECTS ON BIOTA

1. Insects Controlled:

When applied properly, B.t.k. can provide effective controlof forest defoliating Lepidoptera. Foliage protection is theresult of larval mortality and feeding inhibition insublethally-dosed larvae.

2. Effects on Non-Targets:

B.t.k. is a very safe pesticide. No adverse effects havebeen observed on non-target organisms in extensivelaboratory testing after years of world-wide use. B.t.k.does not affect beneficial arthropods, predators, andparasites. Due to its high specificity, B.t.k. does notinterfere with mortality factors which operate naturally inforest ecosystems; B.t.k is therefore very suitable for usein an Integrated Pest Management (IPM) program. Theonly non-target organisms possibly directly affected areother leaf eating lepidopterans that are present at the timeof application (Miller, 1990). However, even within thisrestricted group, B.t.k exhibits a great deal of specificity.Indirect effects on some song birds feeding on caterpillarsof susceptible species are presently under investigation(Barber 1992, personal communication).

• SAFETY

1. Handling:

B.t.k. poses no threat to human health during handling orapplication, but it must be handled in a proper manner.Short term skin or eye irritation and allergic skin reactionsare possible. Inhalation may result in respiratory tractirritation.• Use local ventilation.

• Use approved respirator for dust or mist (if conditionsrequire).

• Wear rubber gloves and chemical goggles or safetyglasses.

2. Product Precautions:

Keep out of reach of children.Avoid contact with skin, eyes, or clothing.

3. Disposal and Storage:• Avoid excessive storage temperatures (43°C) and directsunlight. Consult label for specific recommendations.• Rinse empty containers with water.• In case of spill or release: if possible, recover productand place into appropriate container for disposal; rinsearea with water or absorb with inert material.

• Rinsed containers as well as rinse water should be

disposed of according to provincial regulations.

4. Emergency and Medical Treatment:

• Remove source of exposure.• In case of contact, flush eyes or skin with clear, cleanwater.

• Get medical attention if irritation persists or signs ofdiscomfort continues.

• QUESTIONS AND ANSWERS

Q. Is B.t.k. as effective as chemical insecticides ?

A. After years of wide scale operational experience withB.t.k. and chemical insecticides, there is generalagreement among users that at low to medium insectpopulation densities, B.t.k. provides results comparable tothose achieved with conventional chemical insecticides.

However, B.t. might not be as effective against highpopulations, it has a narrower window of application, andmight be more susceptible to weather conditions afterspray application. Based on field experience in NewBrunswick, it was found that the use of fenitrothion willlikely provide 60% foliage protection, while the use of B.t.will likely provide 50% foliage protection (Deloitte &Touche, 1992). According to experts, improvement inapplication technology could certainly enhance theefficacy of B.t.k.. Research is presently under way toresolve this question (Davies 1993, personalcommunication).

Q. How does B.t.k. compare with chemicalinsecticides in terms of cost ?

A. In 1992, Forest Protection Limited (New Brunswick)

reported that operational costs for B.t.k. applications wereup to 20% more expensive than for chemical applications(Davies, 1992). This price difference can vary from $2.50to $3.00 per nectare depending on the year. Productprices are about $9/ha for B.t.k. and $6/ha for fenitrothion(Davies 1993, personal communication). Although B.t.k. ismore expensive to use, these calculations do not includepossible long term economic and environmental benefitsarising from the use of this microbial insecticide.

Q. Can insects develop resistance to B.t. just asinsects have developed resistance to chemicalinsecticides ?A. There is less chance for insects found in open field andforest populations to develop resistance to insecticidesthan those found in enclosed spaces such as grain silos.Nevertheless, it is known that with heavy repeated doses,resistance can develop under fieid conditions. The onlyknown case of resistance to B.t.k. in the field is thediamond black moth (Plutella xylostella) in Hawaii. Testswith moderately resistant field populations ofdiamondback moth show significant variation in LCso'sand suggest the potential for resistance developmentthrough natural selection (Tabashnik era/., 1991). Otherstudies on gypsy moth (Lymantna dispar) show significantvariation in resistance among wild population and suggestthat these are based on vigor differences in growth anddevelopmental capability. (Rossiter etal. 1990). Morerecently, researchers at the Forest Pest ManagementInstitute were able to select for B.t.k. resistance in a

laboratory population of the spruce budworm (VanFrankenhuyzen and Milne, 1993, personal communication).Therefore, as with chemical insecticides, B.t. should besprayed judiciously and only as needed.

Q. Can B.t. replace chemical insecticides ?A. No, because a very narrow spectrum of insects aresusceptible to the different B.t. varieties. Bacillusthuringiensis var. kurstaki for example, is effective againsta limited range of forest insects with particular feedinghabits (defoliating lepidopterans). There are many forestinsects pest species that are not susceptible to B.t.k. as aresult of their physiology or feeding habits such as thespruce budmoth (Zeiraphera canadensis), the sprucebeetle (Dentroctonus rufipennis), the white pine weevil(Pissodes strobi), the Swayne jackpine sawfly (Neodiprionswainei), and the black army cutworm (Actebia fennica).B.t.k. is not registered for use against these insects.Chemical insecticides are often the only means availableto combat these species Forest managers need bothchemical and microbial pesticides as options forimplementation of a flexible and effective forestprotection strategy.

Q. Is HD-1 the only strain that is effective againstforest pests ?A. As of December 1993, all registered B.t.k. formulationswere based on the HD-1 strain. However there are

hundreds of different B.t. strains and both industry andgovernment are continuously screening these to findmore effective ones. One such strain is NRD-12.However, diet-incorporation assays show no difference inLC50 between the HD-1 and NRD-12 strains to larvae ofspruce budworm (Chonstoneura fumiferana), gypsy moth(Lymantria dispar), eastern hemlock looper (Lambdinafiscellana fiscellaria), and whitemarked tussock moth(Orgyia leucostigma). (Van Frankenhuyzen et al, 1992).Nevertheless, new strains are discovered frequently andformulations based on different strains are expected toappear on the market. Another promising development isthe enhancement of existing strains by geneticmanipulation.

• REFERENCES

1. Addresses of Manufacturer:

Abbott Laboratories, LtdChemical & AgriculturalProduct Division

P.O. Box 6150, Station AMontreal, Quebec,Canada H4T 1Z1

Tel: (519) 855-4868Fax: (519)855-4197

Emergencies: 1-708-937-6100

Novo Nordisk Bioindustnals, Inc.33 Turner Rd.

PO Box 1907

Danbury, CT06813-1907 USATel: (203) 790-2600Fax: (203) 790-2748

Sandoz Agro Canada, Inc.Suite 302, Plaza 4,2000 Argentia RoadMississauga, OntarioL5N 1W1

Tel: (416)821-7850Fax: (416)821-7846

Canadian representative:Tel: (613)374-1070Fax: (613)374-1069

References in the text:

Davies, David. C, 1992. Forest Protection Limited 1992Spruce budworm aerial treatment program report. Reportof the Twentieth Annual Forest Pest Control Forum.

Forestry Canada.

Deloitte and Touche, 1992. Economic benefitassessment of spruce budworm control in EasternCanada. Prepared for the Forest Pest ManagementCaucus. 109 p.

Miller, J.C., 1990. Field assessment of the effects of amicrobial pest control agent on non target Lepidoptera.American Entomologist 36(2): 135-139.

Morris, O.N. et al., 1986. Microbial insecticides in Canada;their registration and use in agriculture, forestry and publicanimal health. Bull. Ent. Soc. Can. 18:2 (supplement) 43 p.

Rossiter, M., W.G. Yendol, and N.R. Dubois, 1990.Resistance to Bacillus thuringiensis in gypsy moth(Lepidoptera: Lymantriidae): Genetic and environmentalcauses. Journal of Economic Entomology 83(6): 2211-2218.

Tabashnik, B.E., N. Finson, and N.W. Johnson, 1991.Managing resistance to Bacillus thuringiensis: Lessonsfrom the diamondback moth (Lepidoptera: Plutellidae).Journal of Economic Entomology 84(1): 49-55.

Van Frankenhuyzen, K., R. Milne, R. Brousseau,and L. Masson, 1992. Comparative toxicity of the HD-1and NRD-12 strains of Bacillus thuringiensis ssp. kurstakito defoliating forest Lepidoptera. Journal of InvertebratePathology 59(2): 149-154.

3. Other References:

Bryant, J. E. and W.G. Yendol, 1991. Depositioncharacteristics of aerially applied Bacillus thuringiensis to ahardwood forest with hydraulic nozzles. Journal ofEconomic Entomology 84(2): 542-551.

Leung, J.W. and A. Sundaram, 1991. Droplet sizespectra and deposits of Bacillus thuringiensis aerialsprays, following application at two volume rates over anoak forest. Journal of Environmental Science and Health,Part B: Pesticides Food Contaminants and AgriculturalWastes 26(5-6): 653-682.

Van Frankenhuyzen, K., 1990. Effect of temperature andexposure time on toxicity of Bacillus thuringiensis Berlinerspray deposits to spruce budworm, Choristoneurafumiferana Clemens (Lepidoptera: Tortricidae). CanadianEntomologist 122(1-2): 69-76.

Van Frankenhuyzen, K. and P.G. Fast, 1989.Susceptibility of three coniferophagous Choristoneuraspecies (Lepidoptera: Tortricidae) to Bacillus thuringiensisvar. kurstaki. Journal of Economic Entomology 82(1): 193-196.

Van Frankenhuyzen, K., C.J. Wiesner, CM. Riley, C.Nystrom, C.A. Howard, and G.M. Howse, 1991.Distribution and activity of spray deposits in an oakcanopy following aerial application of diluted and undilutedformulations of Bacillus thuringiensis Berliner against theGypsy moth, Lymantria dispar L. (Lepidoptera:Lymantriidae). Pesticide Science 33(2): 159-168.

West, R.J., A.G. Raske and A. Sundaram, 1989. Efficacyof oil-based formulations of Bacillus thuringiensis var.kurstaki against the hemlock looper, Lambdina fiscellariafiscellaria (Guen.) (Lepidoptera: Geometridae). CanadianEntomologist 121(1): 55-64.

ACKNOWLEDGEMENTSWe would like to thank the pesticide companies forproviding product labels and material safety data sheetsand also for their review of the manuscript. We also wantto thank the "Societe de protection des forets contre lesinsectes et les maladies" (SOPFIM) and Forest ProtectionLimited for the review of some of the technical aspects.

While the information in this Technical Reference has beencompiled from source materials available at the time ofpublication, the authors disclaim all liability with respectthereto.

Additionalcopies of this publication are available, in Englishand in French, from the

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Canadian Pulp and Paper AssociationForest Environment SectionSun Life Building, 19th Floor1155 Metcalfe StreetMontreal, QuebecCanada H3B 4T6

Tel: (514) 866-6621Fax:(514)866-3035

or from

Canadian Forest ServiceNatural Resources CanadaForest Pest Management InstituteP.O. Box 490

Sault Ste. Marie, OntarioCanada P6A 5M7Tel: (705) 949-9461Fax: (705) 759-5700 12/93

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