The control of Psychoda alternata (psychodidae) in sewage biological filters by application of the insect growth regulator pyriproxyfen

The effectiveness of using the insect growth regulator pyriproxyfen to control the nuisance fly Psychoda alternata on the biological filters at Failsworth Sewage Works, Greater Manchester, was investigated. In the trials, populations of P. alternata in a test filter dosed with insecticide were compared with an untreated control filter. Two trials were undertaken which tested the efficacy of different formulations of the insecticide. In the first trial (August 1991) pyriproxyfen was applied as an aqueous suspension of active ingredient at a concentration of 0.5 mg 1−1. Significant (P < 0.05) reductions in the number of P. alternata adults emerging from the test filter were achieved for a period of 22 d post treatment. Over this period reductions in emergence ranged from 19 to 77%. In the second trial (September 1991) pyriproxyfen was applied as the granular formulation, Sumilarv®, to the surface of the filter, at a dose rate of 77.4 g m−2 of filter area, equivalent to an estimated concentration of 0.42 mg 1−1 in the filter over a 2h period. This produced significant (P < 0.05) reductions in adult emergence for a period of 28 d. Control ranged from 35 to 92%. No adverse effects on the non dipteran filter fauna, the chemical performance of the filter, or on the invertebrates in the river receiving the works effluent, were detected for the two trials.