Relationships between sulfonylurea herbicide treatment of host plants and the performance of herbivorous insects.

Previous work had shown that the sulfonylurea herbicide chlorsulfuron affected the survival of a herbivorous insect species dwelling on a sub-lethally exposed host plant. Further experiments have been conducted to establish whether this negative effect was a single occurrence characteristics for the specific insect-plant interaction and the specific herbicide tested. Three insect-plant interactions were tested for the effects of selected sulfonylurea herbicides, i.e. metsulfuron-methyl, chlorsulfuron and tribenuron-methyl. The species pairs tested were Pieris brassicae/Brassica napus, Gastrophysa polygoni/Fallopia convolvulus and Sitobium avenae/Triticum aestivium. No significant effects on survival and relative growth rate of P brassicae or G polygoni were found when treating the host plants with sulfonylurea herbicides. However, the host plants had a significantly reduced root and shoot growth rate when treated with herbicide. Treating T aestivium with the recommended field rate of metasulfuron-methyl did not cause any change in development time, growth rate or fecundity of S avenae feeding on the host plants. The data presented suggest that the increased mortality observed for G polygoni larvae feeding on chlorsulfuron-treated host plants observed earlier was characteristic for this herbicide and for the specific plant-insect interaction only.