Susceptibility of immature stages of Chrysoperla rufilabris (Neurop., Chrysopidae) to pyriproxyfen, a juvenile hormone analog

Effects of pyriproxyfen (Knack), a juvenile analog, at three concentrations (10, 50 and 100 mg [AI]/l), on survival and development of all immature stages of Chrysoperla ritfilabris (Burmeister), were determined in the laboratory. Pyriproxyfen significantly reduced the survival rates when eggs, first and third instars were treated, but not when the second instars and pupae were treated. When eggs were treated, the two higher concentrations reduced the eggs viability by 33.3-50%, and only 0.0-6.7% developed to adults. The lowest concentration of pyriproxyfen (10 mg [AI]/I) caused high mortality on third instars, not on other stages, indicating the third instar was the most vulnerable stage. Pyriproxyfen had significant effects on development for all immature C. rufilibris that successfully developed to adults with variations among the developmental stages and concentrations. The overall developmental duration from eggs to adults when eggs, first, and third instars were treated were 2.6-4.2, 2.4-4.1 respectively, and 6.0-7.1 d longer than those in water control, respectively. However, the overall developmental durations from eggs to adults were 0.5-1.2 d shorter than in water control when the second instars were treated with pyriproxyfen. The compatibility of pyriproxyfen with natural enemies in integrated pest management programs is discussed.