Comparative Contact Activity and Residual Life of Juvenile Hormone Analogs Used for German Cockroach (Dictyoptera: Blattellidae) Control

Abstract

The contact activity and residual life of fenoxycarb, hydroprene, and pyriproxyfen were evaluated against the German cockroach, Blattella germanica (L.). Clean out and maintenance rates were tested on 3 surface types (tempered masonite, unpainted plywood, and stainless steel), and each was aged for up to 4 mo in laboratory and greenhouse environments. Juvenoid activity was determined by evaluating 2 response variables: the percentage of juvenoid- affected adults and twisted-wing rating of adults. Aging period and juvenoid main effects had more influence on the results than the surface type, environment, or dilution rate. Aging accounted for 28 and 36.1% of the variation for percentage of affected adults and twisted-wing rating, respectively. Juvenoids accounted for 22.7 and 21.7% of the variation, respectively. Fenoxycarb was significantly more active than hydroprene and pyriproxyfen and caused higher percentages of affected adults and twisted-wing ratings. Juvenoids aged in the laboratory were significantly more active than those aged in the greenhouse for the 2 response variables. Juvenoid activity on stainless steel was significantly higher than on all the other surfaces. Overall juvenoid effects for all surfaces produced a high percentage of affected adults (92.5%) and twisted wing rating (4.0) at a 1-d aging period. In the laboratory, only fenoxycarb continued to produce severely affected adults (89-100%) and high twisted-wing ratings (4.6- 4.9) throughout the 4-mo residual aging period for the 3 surface types. Hydroprene residues on stainless steel began to exhibit degradation in the severity of wing twisting at the 30-d aging period, and the activity declined sharply at 60 d. Pyriproxyfen on stainless steel continued to produce severely affected adults (86-100%) and twisted-wing ratings (2.9-4.5) throughout the 4-mo aging period, but pyriproxyfen exhibited a noticeable decline in efficacy at the 60-d aging period on tempered masonite and unpainted plywood. Persistence of the 3 juvenoids was affected by the extreme thermal conditions of the greenhouse. Fenoxycarb persisted for up to 60 d without exhibiting a decline in efficacy with twisted-wing ratings ranging from 3.0 to 3.7 on various surfaces. Fenoxycarb activity declined sharply at the 90-d aging period. The activity of hydroprene and pyriproxyfen was reduced significantly at the 30-d aging period with the percentage of affected adults ranging from 44 to 80% and 35 to 60%, and twisted-wing ratings ranging from 0.5 to 1.5 and 0.5 to 1.2 on various surfaces, respectively. The 3 juvenoids did not cause significant ecdysial mortality at either application rate. At clean out, the percentage of mortality of 5th instars during molting to adults ranged from 2.6 to 8.1 and 0.0 to 6.1 on surfaces aged in the laboratory for 1 and 30 d, respectively. The percentages ranged from 0.0-8.6 and 0.0-4.8 on surfaces treated with juvenoids aged in the greenhouse. Juvenoids have short residual lives when applied on selected surfaces aged under extreme conditions.