Toxicity of isothiocyanates produced by glucosinolates in brassicaceae species to black ville weevil eggs

Control of the black vine weevil, Otiorhynchus sulcatus (F.), with alleloch emicals produced from glucosinolates may be possible; however, plant-derive d isothiocyanates are not readily available for bioassays. Our objective wa s to predict the toxicity of plant-derived isothiocyanates using a model de veloped with commercially available compounds. Contact toxicities of 12 org anic isothiocyanates were determined by dipping black vine weevil eggs into isothiocyanate solutions. Quantitative relationships between the molecular structure of the isothiocyanates and their toxicities were estimated by re gressing lethal concentrations against the compound's respective physiochem ical parameters. Isothiocyanate polarity (log octanol/water partition coeff icient) had the most significant effect on observed toxicities, whereas ele ctronic and steric characteristics were unimportant. Using this linear stru cture-activity relationship, we predict that the highest contact toxicities to black vine weevil eggs will result from glucosinolates producing isothi ocyanates with higher numbers of carbon atoms or those bearing sulfinyl, th io, or aromatic moieties.