Polyvinyl Chloride-Insecticide Pellets Fed to Cattle to Control Face Fly Larvae in Manure123

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Polyvinyl chloride (PVC) pellets containing diazinon, dichlorvos, dimethoate, and dimetilan, and acetone solutions of these insecticides were added directly to cattle manure and fed to cattle to determine effectiveness against larvae of Musca autumnalis De Geer in manure. All insecticides in PVC or in acetone solution were very effective when added directly to manure, producing 100% mortality at 0.0003% in manure. Dimetilan in acetone solution produced 95% mortality at 0.000003%, and diazinon and dichlorvos produced 92 and 100% mortality, respectively, at 0.00003%. Insecticides in acetone solution, fed at 5 mg/kg per day, were not effective larvicides in manure. However, at the same dosage in PVC pellets, these insecticides except dimethoate + fenthion and trichlorfon produced 100% mortality through 4 days after termination of treatment. Diazinon and dichlorvos in PVC, the most promising materials, were effective through the last feeding day at 0.5 mg/kg per day. In further feeding trials with PVC-diazinon and PVC-dimetilan, reduction of pellet size, simultaneous with increasing the number of pellets fed, improved the larvicidal effectiveness of diazinon, but not of dimetilan. Increasing the number of pellets fed, by decreasing the concentration of insecticide in PVC, increased the effectiveness of dimetilan but did not alter the effectiveness of diazinon. Rate of passage of PVC-insecticide pellets through the bovine digestive tract increased with decreasing specific gravity. One-eighth-inch cubes and 1/16-inch cubes, which had almost identical passage rates, were found to pass through more rapidly than 1/32-inchcubes. Time of maximum excretion of PVC-insecticide pellets in manure was not necessarily the time of greatest mortality because of loss of insectide from the PVC pellets and subsequent degradation while in the digestive tract. Shell Chemical Company Animal Health Product V-13 dichlorvos-PVC, fed to a dairy herd for an entire summer at ¼ mg/kg per day, did not control face fly larval development in manure. There was no detectable toxicity to the catlle or residues of dichlorvos in milk.