Variation in Susceptibility of Tree-Feeding Insect Species to Photoactivated Thiophene Insecticides

The contact toxicity of the plant-derived phototoxin, alpha-terthienyl (α-terthienyl) and its cyano-derivative (CN-derivative) was examined with respect to 16 terrestrial, primarily tree-feeding insect species by topical application followed by exposure to near-UV light. The sensitivity of these species to α-terthienyl varied 500-fold. Lepidoptera larvae were sensitive, with the exception of black army cutworm. For 2 species, white marked tussock moth and spruce budworm, the material was more toxic than fenitrothion and carbaryl but less toxic than permethrin. Sawfly species varied videly in susceptibility, whereas adults of coleopteran species were tolerant. The activity of the CN-derivative was generally similar to the parent α-terthienyl to 6 lepidopteran species, in contrast to previously reported results of its higher activity to mosquito larvae.