Comparative Effectiveness and Persistence of Certain Insecticides in Poultry Droppings Against Larvae of the Little House Fly1

A method was developed for testing insecticides against newly hatched larvae of the little house fly, Fannia canicularis (L.), which were exposed continuously to a toxicant mixed in poultry droppings as a culture medium. In screening tests, 13 insecticides were mixed with poultry droppings prior to insertion of the larvae. These materials were: Bacillus thuringiensis, fenthion, coumaphos, dimethoate, Ciodrin® (α-methylbenzyl 3-hydroxycrotonate dimethyl phosphate), diazinon, dicapthon, dimetilan, ronnel, malathion, trichlorfon, carbaryl, and Zytron® (0-2,4-dichIorophenyl O-methyl isopropylphosphoramidothioate). Of these, B. thuringiensis, dicapthon, malathion, and carbaryl were eliminated in the preliminary tests. The remaining materials were compared for initial effectiveness and for persistence in poultry droppings after 48 hr. The toxicants differed in their stabilities in droppings as well as in their initial toxicities. Dimethoate was substantially more effective than any of the other materials tested and it maintained its toxicity well up to 48 hr in the manure. Next to dimethoate, coumaphos and diazinon were about equal in effectiveness as larvicides. In initial effectiveness, the concentrations of toxicants (milligrams of active ingredient per kilogram of droppings) that produced 90% or greater mortalities were: 0.5 dimethoate; 1.0 diazinon and coumaphos; 2.0 trichlorfon, ronnel, fenthion, and dimetilan; 4.0 Zytron and Ciodrin. Forty-eight hours after the toxicants had been mixed with poultry droppings, greater than 90% mortalities to newly hatched larvae added to the droppings were produced by the following levels: 1.0 dimethoate; 2.0 diazinon and coumaphos; 4.0 Zytron, ronnel, fenthion, and dimetilan. Ciodrin and trichlorfon showed poor persistence.