PESTIGIDES VS. HOMY BEES 



It is recognized that pesticides are necessary for the production of a 

 crop of saleable fruit. To obtain a fi-uit set, bees are necessary to trans- 

 fer pollen from the anthers to the stigmas. Consequently it is to the advan- 

 tage of both the fruit grower and the beekeeper to minimize the chances for 

 bee losses through exposure to pesticides toxic to bees. 



Honey bees may be poisoned by contact with sprays or dusts at the time of 

 application, by exposure to residues of pesticides and possibly in a few 

 instances, from a fumigating action. For example, parathion has been reported 

 to have fumigating effects on bees even under field conditions. Since bees 

 collect nectar, pollen and water and carry them to the hive, these materials, 

 if contaminated, are capable of causing loss of brood (immature bees), "nurse 

 bees" and the queen. The extent of damage from poisoned pollen, water and 

 nectar may range from slight (often imperceptible) to loss of the entire colony 

 depending primarily on the toxicity of the pesticide and its peraistance in pollen. 



To obtain information on the effects of pesticides on honey bees in 

 Massachusetts, we established a research project to investigate, among other 

 problems, the effects of these materials on honey bees. We have exposed bees to 

 direct applications and also to deposits and residues of a number of pesticides. 

 Among these were DDT, carbaryl (alone and in combination with certain fungicides), 

 Dylox, Eastern States Garden & Orchard Spray, endosulfan, Guthion, malathion, 

 dieldrin, naled, Imidan, Zectran, dodine, endrin and the microbial formulation 

 Thuricide. 



In these experiments, where bees were sprayed directly, the organic phosphates 

 (including Guthion, naled, Dylox and Imidan) were more toxic than the other 

 materials tested. Carbaryl and endosulfan, while somewhat less hazardous, were 

 not sufficiently so to warrant their substitution for the phosphates. DDT and 

 Thuricide exhibited the least toxicity with the latter causing no discernible 

 mortality. It is of interest to note that some honey bees are becoming resistant 

 to DDT. 



Exposure to dried pesticide residues on foliage yielded variable results 

 depending on materials and dosage. In most instances, bees exposed to deposits 

 on the day of application had an appreciable reduction in length of life. However, 

 deposits of DDT or Thuricide did not cause appreciable reductions in length of 

 life. 



Exposures of honey bees to residues four to five days after application also 

 produced results which varied with the treatment. For example, carbaryl in 

 combination with thirara was more toxic than in similar combination with ferbam 

 or glyodin. Both dieldrin and Guthion residues were highly toxic after four days 

 producing 50 per cent mortality within 36 and 24 hours respectively. The remainder 

 of the pesticide residues did not cause appreciable mortalities after four or five 

 days. 



