Role of light traps

Course: Ag. Ento 510- Integrated Pest Management

Dineshkumar G. Dalvaniya

M.Sc.(Agri) In Entomology

1st Sem.-C.P.College of Agriculture

S.D.A.U

How can a Crop be monitored

• A field crop is monitored to determine a pests economic status or to determine whether a natural enemy is at a level capable of suppressing a pest's population density. So identification of pests and beneficial insects is of prime importance before any control operation is executed.

• Monitoring tools like pheromone, light and sticky traps can be advantageously used. Field scouting adopting fixed plot survey or roving survey should be taken from time to time to monitor the crop in determining whether the pest population attained ETLs.

• Which Products Form Part of The Ipm Strategy

• Different monitoring tools like pheromone traps, light traps, coloured sticky traps

• Preserved specimens of pests, natural enemies, infested plant portions as identification tools

• Bird perches. • Seed dressing chemicals and seed dressing

machines. • Seeds of Resistant varieties. • Ecofriendly insecticides like Neem products and

bio-fungicides like Trichoderma sp. • Natural enemies like Trichogramma egg cards,

and microbial preparations of NPV & Bt. • Soft and target specific pesticides. • Bait preparations. • Good plant protection equipment. • Finally mostly farm based renewable resources

that can enhance the recycling phenomenon of ecosystem should form part of IPM strategy

Light traps

• Light traps are mainly used for attracting moths & other night flying insects which are attracted towards the light. The insects are actively caught or encouraged to enter a trap.

• The simplest light trap consists of a light on a cable handling out side the building. Any bright white or bluish light is suitable although mercury bulb is the best. The effectiveness of the trap can be enhanced if the lamp is positioned beside a white wall or has a white sheet hung next to it.

• If electricity supply is not available then gas lamp or paraffin vapour can be used. Light traps should not be operated during rain because water drops falling on the hot bulb will crack it if it is not protected from rain water.

• Collections of a light trap provide significant clue to the diversity of insects active at night (Southwood and Henderson, 2000), their respective affinity to different wavelengths of light and to understand and predict how populations function (Southwood and Henderson, 2000).

• Such information, if properly documented, could be put to multi-dimensional use by field- researchers, such as, selection of light-traps for attracting specific order of insects. Inspite of the market being flooded with different models of light traps with lightsources varying in their intensity and wavelengths, no scientific data on the trap collection, diversity, number and its efficacy is available for ready use. Such a data could shed light on the insects attracted to specific range of light. In this regard, a comparative analysis of different light trap collections becomes mandatory in order to study the efficacy of different wavelengths of light in attracting insect of specific orders viz., Coleoptera (Sushil et al., 2004),

• Hemiptera (Rai and Khan, 2002; Manimaran and Manickavasagam, 2000), Lepidoptera (Rose et al., 2004), Hymenoptera and Diptera (Nair et al., 2004). Further corelating this data with weather parameters could help to predict the period of maximum insect diversity and activity. In order to make such information available, a complete segregation of the individual trap collection over a period of time on the basis of order and total catch, and simultaneously corelating it with the prevalent weather conditions becomes necessary.

Using Lights to Attract Insects

• A great number of insect species are attracted to light of various wavelength. Although different species respond uniquely to specific portions of the visible and nonvisible spectrum (as perceived by humans), most traps or other devices that rely on light to attract insects use fluorescent bulbs or bulbs that emit ultraviolet wavelengths (black lights).

• Hundreds of species of moths, beetles, flies, and other insects, most of which are not pests, are attracted to artificial light. They may fly to lights throughout the night or only during certain hours. Key pests that are attracted to light include the European corn borer, codling moth, cabbage looper, many cutworms and armyworms, diamondback moth, sod webworm moths, peach twig borer, several leaf roller moths, potato leafhopper, bark beetles, carpet beetles, adults of annual which grubs (Cyclocephala), house fly, stable fly, and several mosquitos.)

• The mosquitoes Ochlerotatus (formerly Aedes) triseriatus, Ochlerotatu (also formerly Aedes) hendersoni, and Aedes albopictus are not attracted to light, however.) Lights and light traps are used with varying degrees of success in monitoring populations and in mass trapping.

• Light traps similar to the one pictured in Figur have been used for several decades to monitor the presence of insects and to determine seasonal patterns of pest density.

• But because pheromone traps are much more specific (they catch only one or a few pest species instead of many) and more convenient, light traps are no longer as widely used. Nonetheless, light traps provide useful information about the timing, relative abundance, or species composition of flights of European corn borer, white grubs, sod webworms, and a few other pests.

• A light trap used to survey nught-flying insects. Most light traps use ultraviolet lamps and capture a wide range of moths, beetles, and other insects.Although numerous companies market devices that use light as a lur for mass trapping or removal trapping, using light to trap out insect infestations is effective in only a few specific situations. One widely used but very ineffective application of light for insect control is the placement of electrocutors or "bug zappers" on lawns or patios. Such uses are ineffective for at least two reasons.

• First, many insects that are attracted to the area around the light traps (sometimes from considerable distances) do not actually fly into the trap. Instead, they remain nearby, actually increasing the total number of insects in the immediate area. Second, these lighted electrocutors attract and kill a wide variety of insects, the overwhelming majority of whi are not pests. The nonpest species killed by such devices include such beneficial insects as the green lacewing, a predator that attacks a variety of plant pests.

• Insect electrocutors can be effective in certain indoor situations, especially in food warehouses, processing plants, and restaurants. In these facilities, electrocutors are placed in otherwise dimly lit areas where their light is not visible from outdoors. In such locations the trap does not lure insects into the building, yet it does attract and kill certain flies, moths, and beetles that are pests of stored products or nuisances in food production areas (see Gilbert, 1984).

• These traps can also be used somewhat effectively in barns and stables to reduce some fly and mosquito infestations. The efficiency of electrocutors in such situations appears to be low, however, and they must be positioned so that they do not attract insects into a building from outdoors.

• Although using electrocutor-light traps outdoors is not efficient, the placement of outdoor lights can be important. Positioning outdoor lights away from entrances, windows, or other openings reduces problems associated with insect activity around the lights.

• Flood lights directed at loading docks, for instance, do not lure insects into food warehouses as so overhead lights mounted just inside the loading dock door. Placing outdoor lights several feet away from doors of homes and apartments also concentrates insect activity away from the sites where they cause the most annoyance. In addition, yellow light bulbs attract fewer insects that white incandescent lights or fluorescent bulbs.

UV – LIGHT TRAP FOR GRAIN STORAGE GODOWNS

• The UV light trap can be placed in food grain storage godowns at 1.5 m above ground level, preferably in places around warehouse corners, as it has been observed that the insect tends to move towards these places during the evening hours. The trap can be operated during the night hours.

• The light trap attracts stored product insects of paddy like lesser grain borer, Rhyzopertha dominica, red flour beetle, Tribolium castaneum and saw toothed beetle, Oryzaephilus surnamensis in large numbers. Psocids which are of great nuisance in godowns are also attracted in large numbers. Normally 2 numbers of UV light trap per 60 x 20 m (L x B) godown with 5 m height is suggested.

• The trap is ideal for use in godowns meant for long term storage of grains, whenever infested stocks arrive in godowns and during post fumigation periods to trap the resistant strains and left over insects to prevent build up of the pest populations. In godowns of frequent transactions the trap can be used for monitoring.

• Management of white grub beetles through light traps

• White grubs are the cosmopolitan insect pests of agriculture, forest and pasture lands. The pest causes severe economic loss in upland paddy, finger millet, barnyard millet, maize, potato and many other vegetables, fruits and fodder crops in the hills of north-western Himalayan region, where nearly 40 species of this phytophagous pest were recorded.

• The beetles emerge from soil from May to October. To combat the problem, VPKAS, Almora, designed a user-friendly low cost (Rs 570), light trap for efficient mass trapping of beetles, to reduce the population of white grubs in soil. Deployment of 61 light traps in different villages of Almora district on community basis led to trapping of beetles 114,000 in Darima, 67,900 in chausali. 46,600 in Tipola-Tunakot, 88,900 in Daulaghat-Govindpur, 76,100 in Manan and 31,400 in Bhagartola village from June to September 2006.

• These light traps have become popular amongst the farmers of this region, as a result of which 250 units of the trap were sold to the farmers and other agencies Black Light for Monitoring Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) in Tomato The use of black light traps to monitor adult tomato fruitworm, Helicouerpa zea (Boddie), night activity is useful for dictating the need for insecticide applications for this insect on tomatoes (Lycopersicon esculentum Miller)

• the need to relate black light trap catches to oviposition for prediction of peak populations in individual fields. They found oviposition by H. zea to be more closely related to the number of males rather than females caught in black light traps.

INSECT ORIENTATION TO VARIOUS COLOR LIGHTS IN

THE AGRICULTURAL

• This experiment was conducted at night from 9.00 to 9.30 hours in the dark during the year In order to cover diversity of crops and forest vegetation All six lights were arranged in line at 6 meter apart from each other to let the insect to orientate toward their most favorite light color.

• All lights were simultaneously kept on for half an hour and each of them was suitably projected on white fabric screen. The fabric screens were placed separately on stands almost one meter high above ground to be visible from distance. Plastic tub containing soapy water was placed under each light to gather the attracted insects. Soft brush was used to push the insects down in tubes. At the end of experiment, insect material of each tub was transferred to properly labeled bottles (with color light, site, date and time etc.) containing 10% alcohol and collection was transferred to laboratory for identification In the laboratory, contents of each collection bottle were added in a large dish separately,

• exact number of insects was counted and each of them was identified for respective insect order. The same procedure was adopted for all six collection bottles containing insect collection gathered at each light color. Most of the insects were identified by naked eye and field lens (10x) was also used where needed to confirm the diagnostic feature of smaller insects.

• Total numbers of insects caught at each colored light. The experiments E1 and E2 were repeated twice at each site. Total collection of insects per light color was added up separately for each experiment and then percentage of insects attracted at each light spectrum was computed to be tabulated in Table 1 .

• Finally the percentage of insects oriented toward different light colors during both experiments E1 and E2 were separately added for respective light colors to compute the cumulative percentage of insect attracted per light color for more comprehensive and precise results.

• According to the cumulative percentages of insect collection gathered per light, the lowest number of insects has been attracted at red color light i.e. 2.3%. Back light attracted the highest figure of 46.5% insects. Blue light was rated to attract the second highest insect numbers of 20.35% during both the light experiments conducted at different sites. The Chi-square calculation of 3814 is greater than the chi-square critical value of 15.1 (d.f= 5, p.=0.01). This is a highly significant difference supporting the hypothesis that different wavelengths of light will attract different number and variety of insects

• Table 1: Percentage of insects attracted at different colored light during night hours in the field

Red 2.20%

Yellow 10.60%

Green 4.70%

White 18.00%

Black 42.10%

Blue 22.40%

Total insects caught

1020