Effects of precocenes (I and II) and juvenile hormone I on Spodoptera littoralis (Boisd.) (Lep., Noctuidae) larvae parasitized by Microplitis rufiventris Kok. (Hym., Braconidae).

Precocenes I & II (PI & PII) and juvenile hormone I (JHI) were topically tested on unparasitized and Microplitis rufiventris parasitized Spodoptera littoralis larvae. Parasitism interferes with normal host response to these compounds, decreasing their effectiveness. In all cases, the effect was dose-dependent. In contrast to PII or JHI, the lower dose of PI was more effective than the higher one. Application of JHI to S. littoralis larvae was less harmful to parasitoid development than either PI or PII. It is therefore emphasized that the commercial utilization of insect growth regulators should be undertaken carefully to minimize possible disruptive effects on developing parasitoids. [ABSTRACT FROM AUTHOR]