RATE DETERMINATION, INDIRECT TOXICITY, CONTACT ACTIVITY, AND RESIDUALPERSISTENCE OF LUFENURON FOR THE CONTROL OF THE GERMAN-COCKROACH (DICTYOPTERA, BLATTELLIDAE)

Three interrelated laboratory and greenhouse studies were conducted fo r the chitin synthesis inhibitor lufenuron to determine dose-activity, indirect toxicity, contact activity, and residual persistence against the German cockroach, Blattella germanica (L.). Lufenuron activity wa s determined by evaluating 3 response variables (percentage of molt in hibition, percentage of affected adults, overall percentage of mortali ty). These variables were unified in a dose-response rating score (the mean effects rating). In the rate determination study, differences in lufenuron activity on different surfaces (clean masonite, oily-frass masonite, unpainted plywood) had more effect on the results than did t he application rate (10, 25, 50 mg/m(2)), life stage (3rd or 5th insta rs), and exposure time (15, 30, 60 min). Percentage of molt inhibition and the effects ratings were significantly greater at 25 and 50 mg/m( 2) than at 10 mg/m(2). No differences in percentage of affected 4th in stars or adults were found between 3rd and 5th instars, however, highe r effects on 5th instars were observed for percentage of molt inhibiti on, overall percentage of mortality, and effects rating. There was a s ignificant effect on oothecal production from females exposed to lufen uron deposit during oogenesis. The number of viable oothecae decreased , the number of aborted oothecae increased, nymphal hatch decreased, n ymphal survival at 7 d after hatch decreased, and nymphal survival of the 1st molt decreased with an increase in the rate at each exposure t ime. In indirect toxicity tests, lufenuron activity significantly decr eased with a decrease in the ratio of exposed to unexposed cockroaches . Exposure time had no effect on the indirect toxicity of lufenuron am ong cockroaches. In residual persistence tests, surface had more influ ence on the results than the environment, rate, or residual aging peri od. Lufenuron was most active on masonite, with deposits on plywood be ing more active than on oily-frass masonite. Residues aged in the labo ratory were significantly more active than those aged in the greenhous e for most response variables and effects rating. A rate of 25 mg/m(2) was significantly different from 10 mg/m(2) for most response variabl es and effects rating. Effects rating reduced significantly at 6 and 1 2 mo of aging. Surfaces produced significant effects in all response v ariables until 9 mo of aging. After 12 mo, lufenuron activity on plywo od and oily-frass masonite declined significantly compared with the ac tivity on Masonite.