PESTICIDE POISONING IN HONEY BEES
The use of pesticides has become inevitable in modern agriculture. During the last four decades, the consumption of pesticides in India has increased several folds. Pesticides used on field crops for the control of pests have their side effects, one of which is toxicity to ho ney bees. Honey bees are susceptible to many pesticides. Three types of harmful effects evident in agriculture are loss in production of honey,
contamination of bee products, reduction in the yield of cross pollinated crops.
The harmful effects may be due to the direct exposure of honey bees to pesticides or through indirect contact with their residues. Direct exposure occurs from treatment of bee hives for disinfestation purpose or bees visiting the field at the time of spray. While the indirect exposure occurs from the spray drift or bee foraging in sprayed crops.
Symptoms of bee poisoning
- Dead bees near the entrance of hive or colonies
- Dead bees on the top of frames or bottom board
- Lack of recognition of guard bees
- Aggressiveness
- Fighting among bees
- Paralyzed bees crawling on nearby objects
- Sudden decline in food storage and brood rearing
- Dead and deserted brood in the hive
- Poor recognition of pollen and nectar by bees
- Depleted population of the colony
- Finally results in contamination of bee products
Causes of poisoning
- Pesticide application during crop bloom
- Drift of toxic chemicals on to flower, pollen and nectar
- Bee feeding on contaminated food and water sources
- Use of broad spectrum insecticides (chlorinated hydrocarbons, synthetic pyrethroids)
- Type of formulation used like dust, EC which are more harmful than WP and granules
- Types of spray, fineness of spray, stage of crop, weather condition and age of the colony
- Use of insect growth regulators may inhibit brood production
- Herbicides indirectly affect through damage to the foliage
- Use of diesel oil as a carrier in insecticide formulations
Management of bee poisoning
The basic principle in the management of bee poisoning is to avoid the exposure of honey bees to toxic effects. This could be achieved with the help of both bee keepers and the farmers. The practices to be followed by bee keepers include the following.
- Bee colonies should be maintained where use and drift of pesticide is minimum
- Close co-operation with farmers to avoid irrational use of pesticides
- Feeding of colonies with sugar syrup at the time of pesticide application to reduce bee foraging
Management practices to be followed by the farmers includes the following
- Need based use of pesticides
- Informing the bee keepers in advance about the spray programme
- Use of less hazardous, selective and repellent (methyl Salicylate, R-874) insecticides
- Spraying in the evening when the bee activity subsides
- Granules, EC are preferred compared to dusts
- Avoid formulations with attractants like Sevimol during crop bloom period
- Development of bee strain resistant to toxic effects of pesticides
- Addition of adjuvant Sylgard 309 silicone surfactant to reduce the bee mortality.
Less hazardous insecticides
- Granules: Fenthion, phorate, aldicarb and lindane
- EC: Endosulphan, phosalone, fluvalinate, menazon and lindane
Highly hazardous insecticides
- Dust: Carbaryl, diazinon and fenvalerate
- WP: Carbaryl
- EC: Chlorpyriphos, cypermethrin, deltamethrin, diazinin, diChlorvos, dimethoate, ethion, fenitrothion, fenthion and fenvalerate.
- SL: Imideacloprid
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