Enhanced fumigant toxicity of p ‐cymene against Frankliniella occidentalis by simultaneous application of elevated levels of carbon dioxide

The fumigant toxicity of the essential oil component p ‐cymene was assessed against Western Flower Thrips, Frankliniella occidentalis. F occidentalis adult females, first‐ and second‐instar larvae and eggs were exposed for 2, 24 and 48 h to combinations of three p ‐cymene doses and two carbon dioxide levels (ambient, 10%). Additional experiments were conducted on F occidentalis adult females with lower carbon dioxide levels (ambient, 2%, 4%, 6%) applied in combination with p ‐cymene. Combined applications of p ‐cymene and carbon dioxide were found to increase significantly the fumigant toxicity of p ‐cymene against both adult female and larval thrips, but not thrips eggs. An increase in exposure time also led to an increase in adult and larval mortalities in both the p ‐cymene alone and combined treatments. These results indicate that by combining applications of the essential oil component, p ‐cymene, with increased carbon dioxide, it may be possible to achieve toxicity levels similar to those of standard chemical fumigants. © 2001 Society of Chemical Industry