BEE POISONING from Pesticides
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How to Reduce BEE POISONING From Pesticides PNW518 A Pacific Northwest Extension Publication Washington • Oregon • Idaho How to Reduce Bee Poisoning from Pesticides By D.F. Mayer, Ph.D., Washington State University Cooperative Extension entomologist, Prosser; C.A. Johansen, Ph.D., Washington State University Cooperative Extension entomologist, retired and C.R. Baird, Extension entomologist, University of Idaho CAUSES OF BEE POISONING such bees may take two to three days to die. Bee- keepers familiar with Sevin poisoning quickly Most bee poisoning occurs when insecticides are learn to recognize the “crawlers” that move about applied to crops during the blooming period. in front of the hive but are unable to fly. Dead brood Other hazards are in or in front of the hive is typical of Sevin, micro- encapsulated methyl parathion (Penncap-M), or • Drift of toxic pesticides onto adjoining crops or arsenical poisoning. When not enough hive bees weeds that are in bloom. are left to cover the brood frames or care for the • Contamination of flowering cover crops when brood, desiccation or starvation kills the larvae. In orchards are sprayed. severe cases, few bees in the hives survive, or the • Insecticidal dusts adhere to foraging bees and entire colony may be dead. ultimately become packed with the pollen onto the hind legs. Penncap-M and Sevin are espe- One forager returning to the hive with a load of cially dangerous because they may be stored contaminated pollen or nectar can cause extreme with pollen and kill newly emerged workers the agitation and death of a number of bees. Several following season. such foragers can seriously disrupt and damage • Bees drinking or touching contaminated water the colony. Often, the queen is superseded because on foliage or flowers. of the agitation of the workers, possibly aggravated • Bees collecting contaminated pollen or nectar. by a reduction in the secretion of queen substance. Queens may be affected, especially by slow-acting BEE POISONING SYMPTOMS materials such as arsenicals, Sevin, and micro- encapsulated methyl parathion (Penncap-M), The most common symptom of bee poisoning is which may be taken into the hive with pollen. the appearance of excessive numbers of dead bees Queens may behave abnormally: for instance, lay in front of the hives. Another common symptom eggs in a poor pattern. Severely weakened or is lack of foraging bees. Aggressiveness in bees queenless colonies will not live through the follow- may be caused by most pesticides. Stupefaction, ing winter. Queenlessness the following fall have paralysis, and abnormal activities of bees are com- been associated with the use of a wide variety of monly caused by chlorinated hydrocarbons and insecticides including arsenicals, Penncap-M, Sevin, organophosphorus insecticides. Regurgitation of and parathion. Typically, severe Sevin or Penncap- the honey stomach contents is often caused by poi- M poisoning makes at least half of the colonies soning with organophosphorus insecticides. Bees queenless within 30 days. may perform abnormal communication dances on the horizontal landing board at the hive entrance while under the influence of insecticide poison- BEEKEEPER-GROWER ing. Disorganized behavior patterns may lead to COOPERATION lack of recognition of affected field bees by guard bees. A major consideration for the reduction of bee poisoning is beekeeper-grower cooperation. Many Many bees poisoned with Sevin or dieldrin slow cases could be cited where a grower, simply down and appear as though they had been chilled; through ignorance of the hazard to bees, has 3 caused tremendous damage to a large number of less hazardous than aerial application because colonies. The timing or materials of the pest con- less drift of the pesticides occurs, and smaller trol program could have been modified so that little acreages are treated at one time. or no poisoning occurred. In many cases this can be done without unduly increasing the control cost • Apply certain chemicals only in late evening, or inconveniencing the grower. night, or early morning while bees are not actively foraging (generally between 6 p.m. and Beekeepers should get acquainted with the farmer 7 a.m. in the north and 8:30 p.m. to 4 a.m. in the on whose land they place hives. They should know south). Evening applications are generally less about pest-control practices and other special prob- hazardous to bees than early morning applica- lems that might occur. tions. When high temperatures cause bees to start foraging earlier or continue later than usual When the grower rents colonies for crop pollina- (5:30 a.m. to 8:00 p.m.) shift time accordingly. tion, definite verbal or written agreements can be made. One type of written contract emphasizes • Do not apply insecticides when temperatures are crop production and has the desirable effect of expected to be unusually low following treat- encouraging closer cooperation between the ment or on nights when dews occur. Residues grower and the beekeeper. Such contracts should will remain toxic to bees for a much longer time include details of the responsibility of the bee- under such conditions. keeper in providing strong and effective colonies and of the farmer in safeguarding the bees from • Do not dump unused dusts or sprays where they poisoning. In modern agriculture, the beekeeper might become a bee poisoning hazard. Some- often depends on the grower for bee forage and times bees collect any type of fine dust material the grower depends on the beekeeper for pollina- when pollen is not readily available. Under such tion. Cooperation and understanding of each conditions, they may actually carry pesticide other’s problems are essential. dusts back to the colony. • Use insecticides that are relatively nonhazardous REGULATIONS to bees whenever such choices are consistent with other pest control considerations. Many states have regulations that attempt to reduce the hazard of insecticide applications to bees. These • Choose the less hazardous insecticide formula- are based on the safest timing and bloom conditions tions. Our tests have consistently indicated dusts for given chemicals on given crops. Note: Some of are more hazardous than sprays of the same the listed pesticides have been discontinued and insecticide. Emulsifiable (liquid) formulations are no longer available or legal to use. usually have a shorter residual toxicity to bees than do wettable powders. Granular formula- tions are low in hazard to bees. REDUCTION OF BEE POISONING • Contact and ask the beekeeper to remove colo- Following are some of the ways to help reduce bee nies from the area (or keep the bees confined poisoning: during the application period) before applying hazardous pesticides when such measures are What the Pesticide Applicator Can Do feasible and of value. • Do not apply insecticides that are toxic to bees • When roadside and other weed control opera- on crops in bloom, including cover crops in tions involve 2,4-D and similar compounds on orchards and adjacent crops or interplants. With blooming plants, select the formulations or aerial application, do not turn the aircraft or derivatives known to be least harmful to bees. transport materials back and forth across blos- Our tests have shown that at maximum dosage, soming fields. Ground application is generally alkanolamine salts and isopropyl esters are more 4 toxic than other forms. Oily formulations seem phone number in printing large enough to be to be more hazardous to bees. Spraying in late read at some distance in all apiaries so you can afternoon or evening will also lessen the hazard, be contacted readily to move the colonies when since bees will not visit the blooms after they hazardous sprays are to be applied. Several regu- become curled. The only highly toxic herbicides lations concerning such marking of apiaries are are arsenicals and DNOSBP. in effect in the Pacific Northwest. • Observe State Department of Agriculture regu- • Do not move hives back into fields treated with lations aimed at reducing bee poisoning. hazardous insecticides until at least 48 to 72 hours after the application. Our tests have shown What the Grower Can Do that 50% to 90% percent of the killing of bees by insecticides occurs during the first 24 hours • Mow or beat down orchard cover crops before after application. applying sprays hazardous to bees. Treatment with 2,4-D is the best way to remove dandelion • Choose apiary sites that are relatively isolated blooms. This is especially important in relation from intensive insecticide applications and not to the first cover spray on apples, applied dur- normally subjected to drift of chemicals. Estab- ing a critical foraging period when bees will fly lish holding yards of honey bee colonies at least several miles to obtain pollen and nectar from 4 miles from orchards being treated with toxic even a few blooms of dandelion, or mustard. materials. • Blossom-thinning sprays have not been hazard- • Learn about pest control problems and programs ous to bees in Washington orchards. However, so you can develop mutually beneficial agree- Sevin used as a fruit thinner can be hazardous if ments with growers concerning pollination ser- cover crop blooms become contaminated. vice and prudent use of pesticides. • Learn the pollination requirements of the crops • Be careful how you control insect pests around you raise. Such information is not generally beekeeping storage facilities or apiaries. Vapona known for some insect-pollinated crops, such as “No Pest Strips” will also contaminate beeswax lima beans. Application of insecticides hazardous and kill bees when the combs are put in colonies to bees on these crops, or driving beekeepers out later. Use relatively low-hazard materials, such of your area by the use of insecticides on other as Sevin bait granules for ant control and pyre- blossoming crops will likely cause poor yields. thrum aerosols for fly control.