Susceptibility of poultry biting lice (Mallophaga) to Dipel and bacilan (Bacillus thuringiensis)

Dipel (Abbott Laboratories, N. Chicago, U.S.A.) and Bacilan (PPR, Walcz, Poland), commercial preparation of Bacillus thuringiensis var. kurstaki, containing 16,000 IU/mg were tested in vitro on Menopon gallinae (L.) and Eomenacanthus stramineus (Nitzsch). The insects were placed in feathers, in Petri plates, and sprayed with 0.25, 0.5, 0.75, 1, 2, 4 and 10% solutions of insecticides. Each concentration was tested on a group of 10 insects, in three replications. The viability was observed after 10, 20, 30, 60 min and then 10 times within 1 hr intervals. Dipel was effective in lower concentrations [LC50 = 2.2 (1.4-3.5)% against E. stramineus and 2.9 (1.8-4.6) against M. gallinae]. LC50 of Bacilan were 2.9 (1.8-4.3) for E. stramineus and 3.2 (2.5-4.0)% for M. gallinae respectively. The ingestion of microbial insecticides was proved by the presence of spores B. thuringiensis in the insects being previously exposed to indirect activity of 2.2% Dipel and 2.9% Bacilan. Moreover, the growth of B. thuringiensis colonies in the lice culture was observed. 3% Dipel solution proved to be effective in killing the insects on the host, but no earlier than after the second application within 24 hr intervals.