Susceptibility of Sunn pest in overwintered adults and new generation to eight insecticide groups of IRAC

Wheat is the most important strategic crop in Iran and the world. Sunn pest Eurygaster integriceps Puton (Hemiptera: Scutelleridae) causes a lot of damage annually. Currently, two groups of IRAC insecticides including pyrethroids and organic phosphorus compounds are recommended against this pest in Iran and other countries infested with the Sunn pest. In this research, different insecticides were selected from the eight insecticide groups of IRAC, and contact bioassay was carried out on two life stages of the Sunn pest. The results showed that among the tested insecticides, Deltamethrin (LC50=2.93 mg a.i./L) as a pyrethroid group, had the most contact toxicity among chemical compounds against overwintered adults of the Sunn pest, and Fenitrothion as an organic phosphorus compound  (LC50=19.4 mg a.i./L) was ranked in the second group. But on the new generation of the Sunn pest, both insecticides were ranked in the same group at 72 hours after exposure (LC50=4-4.6 mg a.i./L). Further investigations revealed that among neonicotinoid insecticides, Thiamethoxam had more contact toxicity and ranked in the next group. Mortality comparison of different insecticides in high concentration (60-20000mg/L) based on commercial formulations showed that Deltamethrin and Fenitrothion insecticides caused 90-100% mortality in both life stages of the Sunn pest. The new insecticides, Spirotetramat, Flonicamid, and Chlorantraniliprole did not show acceptable effectiveness 72 hours after exposure on overwintered and new-generation adults (3.3-43%). Therefore, most of the new insecticides tested for the chemical control of the overwintered and the new generation adults did not have acceptable mortality, and only thiamethoxam insecticide can be studied on Sunn pests in field conditions.