بررسی اثرتغییر pH آب مصرفی بر سمیت ایمیداکلوپراید و دیمتوات روی شته جالیز Aphis gossypii در مزارع پنبه شرق استان گلستان

Aphis gossypii Glover (Aphididae: Hemiptera) is one of the important pests in cotton crop. The adults and nymphs by sucking the sap, cause damage. This pest by secretion of honeydew on plant surface, cause the growth of black sooty molds that prevents photosynthesis of plants. They also carry some plant viruses. The use of pesticides is one of the main methods to control this pest. The characteristics of water used as a carrier of pesticides may affect the effectiveness of them. One of the most important characteristics is, the pH of water. Some pesticides lose their effectiveness due to chemical reactions under acidic or alkaline conditions. Therefore, at present research, the effectiveness of Imidacloprid SC 35% (0.25 ml per hectare) and dimethoate EC 40% (1L/1000L) were avaluated against the aphids under three level of water pH (5.5, 7.5, and 9.5), in field conditions 3, 7 and 14 days after spraying. The analysis of data was done with the help of Henderson-Tilton formula. In addition, a fixative was used to change the pH of the consumed water.The results showed that imidacloprid at 7.5 pH and 7 days after spraying caused (78.04±5.68%) effectiveness and dimethoate at 5.5 pH, and 3 days after spraying (85.01 ±4.96%) effectiveness, in controling the pest. The lowest effectiveness (12.54±4.01 and 11.24±5.09%) was absorbed at 9.5 pH and 14 days after spraying, respectively. Therefore, it can be concluded that due to the fact that these two insecticides are from two different groups, they have shown different behavior with pH changes; The important thing about these two insecticides is that with the increase in pH to more than 8, the efficiency of both insecticides has decreased drastically.