Comparison of the susceptibility of two populations of Sunn pest, Eurygaster integriceps to Deltamethrin and fenitrothion

Sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae) is the most important pest of wheat and barley in Iran. The aim of this study was to determine the resistance probabel levels of summer populations of Sunn pestcollected from Varamin (under the pressure of insecticides) and Gonbad (with no history of insecticide application) regions. Toxicity of the insecticides for the collected adults was measured using a topical bioassay. Treatments were performed under the pronotum with each insecticide in acetone for treatments and acetone alone for the control. The treated insects were maintained in laboratory conditions and mortality was recorded 24 hours after treatment. Fenitrothion LD50 values for Gonbad population males and females were 26.27 and 26.8 ug/insect, respectively. Varamin population LD50 values were also estimated 135 and 157.11 ug/insect for fenitrothion, respectively. LD50 values for deltametrin estimated for males and females of Gonbad population were 0.025 and 0.15 ug/insect. The values were also estimatid 0.47 and 1.75 ug/insect for males and females of Varamin population, respectively. Based on the overall results, Sunn pest showed reduced susceptibility of Varamin population to both insecticides studied. Although the susceptibility to deltamethrin was higher, its resistance ratio was also higher than fenitrothion concerning the probability of resistance development. The results obtained can be useful in Sunn pest control programs.