EFFICACY AND HISTOPATHOLOGY OF INSECT CHITIN INHIBITORS ON CHIRONOMID MIDGES

Two insect chitin inhibitors, diflubenzuron (1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea) and Bay SIR-8514 (1-(4-trifluoromethoxyphenyl)-3-(2-chlorobenzoyl)-urea) were bioassayed against two species of chironomid midge, Chironomus decorus Johannsen and Tanypus grodhausi Sublette to determine the level of activity of each compound against each species of midge and record the effects of each compound on the morphology and histology of each species.; Cultures of both species of midge were maintained in the laboratory, and larvae from these cultures were utilized for testing. Diflubenzuron and Bay SIR-8514 were bioassayed against each species in each larval stadium, elucidating the LC(,50) and LC(,90) values. From those individuals that died, observations were recorded on the resulting morphological anomalies that might occur, and dead individuals were also fixed in various tissue fixatives to study the histopathology that resulted from treatment with the two insect chitin inhibitors.; It was found from the bioassay studies that C. decorus was approximately five-fold more susceptible to diflubenzuron than to Bay SIR-8514, but displayed greater morphological and histopathological anomaly to Bay SIR-8514. However, T. grodhausi was found to be approximately ten-fold more tolerant to both compounds than C. decorus. T. grodhausi, although displaying some measure of morphological and histopathological anomaly to Bay SIR-8514 did not produce the typical "humpback" condition found in C. decorus treated with Bay SIR-8514. The morphological anomlay was a function of concentration and only occurred in the higher concentrations. It was found that larvae survived the molt in the higher concentrations might die in the next larval stadium due to the inability to feed. Affected larvae failed to ingest food and ultimately died, presumable from starvation.; It was found that both compounds caused pathology in the ventriculus (midgut) as well as the hindgut. However, effects in the ventriculus were of a greater magnitude than to either the foregut or hindgut. Included in this treatise is a study of the comparative anatomy and histology of C. decorus and T. grodhausi.