Cotton allelochemics, such as gossypol and the volatile terpenes caryophyllene and caryophyllene oxide, inhibit the growth of Heliothis virescens larvae when incorporated into an artificial diet. H. virescens call cultures could provide a rapid, less expensive bioassay for these compounds. Cytotoxicity of these terpenoids, when administered as single compounds in cell culture, mimic the results obtained from feeding studies in which larvae ingest these terpenoids in an artificial diet. The order of toxicity from both in vivo and in vitro experiments was gossypol > caryophyllene oxide > caryophyllene. However, the cytotoxicity of these compounds as binary mixtures did not follow the results obtained in artificial diet studies with larvae.