Laboratory experiments with juvenoids on the San Jose scale, Quadraspidiotus perniciosus Comst.
When 0.001-1% acetone solutions or aqueous emulsions of the juvenile hormone analogues SJ-53 (ethyl 11-chloro-3,7,11-trimethyl-2-dodecenoate), hydroprene, methoprene, triprene, kinoprene and R-20458 [(E)-3-[5-(4-ethylphenoxy)-3-methyl-3-pentenyl]-2,2-dimethyloxirane] were applied to immature apples and shoots of red currant infested with second-instar larvae and pronymphs (prepupae) of the overwintered and summer generations of Quadraspidiotus perniciosus (Comst.) in laboratory tests in Hungary, the analogues at 0.01 or 0.1% induced relatively high mortality of males but only moderate mortality of females. Males died mostly as nymphs (pupae), and females as young unproductive adults. At low concentrations, the natural hymenopteran parasites of the scale were not apparently affected by the juvenoids. At the highest concentration, which proved effective against both sexes of the scale, parasite emergence was significantly reduced. The data indicated that selective juvenoids could be used successfully as control agents for males of the overwintered generation in the pronymphal and nymphal stages.