Comparison of Susceptibility of Melon Aphid, Aphis gossypii Glover (Hemiptera: Aphididae), to Pirimicarb and Malathion in Seven Regions in Iran

The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is one of the most important pests of agricultural products in Iran. In this study, susceptibility of melon aphid that collected from seven regions (Yazd, Varamin, Mohammadshahr, Esfehan, Karaj, Hashtgerd and Ramsar) was compared to pirimicarb and malathion after 24 hours in 2009. Bioassay experiments on adults were carried out by using leaf dipping method on squash (Cucurbita pepo) leaf in different concentrations of insecticides in laboratory conditions (25 ± 0.2 ºC, 60 ± 5%, 16: 8 [L: D] h). Control treatment was dipped in distilled water. Each test was replicated three times. The results showed that LC50 values of malathion for Ramsar, Karaj, Mohammadshahr, Hashtgerd, Varamin, Esfehan, and Yazd populations were 162.99, 159.19, 117.94, 79.96, 38.81, 36.32, and 20.25 ppm, respectively. Also, LC50 values of pirimicarb for Yazd, Mohammadshahr, Kararj, Hashtgerd, Ramsar, Esfehan, and Varamin populations were 1414.16, 1359.34, 1057.62, 970.33, 881.87, 806.14, and 601.98 ppm, respectively. According to results, aphids of Varamin and Yazd populations had the most susceptibility to pirimicarb and malathion, respectively. Also, aphids of Yazd and Ramsar populations had the least susceptibility to pirimicarb and malathion, respectively. Regarding the fact that Yazd and Ramsar populations had the least susceptibility to pirimicarb and malathion, respectively, there is a possibility that melon aphids in these regions are susceptible to other organophosphate and carbamate (similar mode of action) pesticides. Therefore, in the pest management program, careful chemical control measures for melon aphid in these regions is recommended.