D3013: Fumigant toxicity of linalool against thrips (Thysanoptera: Thripidae) as affected by polymer release and adjuvants

We assessed the fumigant toxicity of linalool against thrips through fumigation bioassays. Two species of thrips, Frankliniella occidentalis and F. insularis were fumigated by incorporating linalool into polyacrylamide hydrogels, to which thrips were exposed in fumigation chambers. Hydrogels contained only (R)-linalool or a binary mixture of (R)-linalool and one of nine other oils: (S)-linalool, peppermint, cedarwood, neem, clove, coconut, jojoba, soybean or olive oil. The least saturated hydrogels were more toxic, regardless of the enantiomer of linalool with which they were conditioned. The R enantiomer was twofold more toxic to F. insularis than the S enantiomer. Similarly for F. occidentalis, the R enantiomer was significantly more toxic than the S enantiomer. Peppermint oil and (R)-linalool was the only synergistic mixture, while the other oils acted to varying degrees of antagonism. F. occidentalis was significantly more resistant than F. insularis to all treatments. Further studies are warranted to identify additional synergists and to determine the efficacy of fumigation via polymer release under field conditions.