Toxicity and biochemical effects of some pesticides on the pistachio psyllid, Agonoscena pistaciae (Hem.: Psyllidae) in the field conditions

The common Pistachio psylla, Agonoscena pistaciae, is one of the most important pests that feeding on the sap both in nymphal and adult stage. In this study, the effects of spirodiclofen, spinosad, azadirachtin and Thymol soap were studied on the psyllid nymphs. At the same time, the impact of these pesticides on the activity of esterase and glutathione S-transferase (GST) enzymes were studied. In this research, three doses of each pesticide were selected (Recommended dose, 2-fold recommended dose and 1/2 recommended dose). The results showed that thymol soap had better performance in controlling pistachio psylla with concentration of 2000 mg/l compared to other pesticides. The populations of nymphs were reduced to 95.40, 94.12, and 82. 30, 55.51 and 29.48 percent at 1, 3, 7, 14 and 21 days after application. The biochemical results of this study showed that spirodiclofen, spinosad, azadirachtin and Thymol soap, had the greatest impact on the inhibition of esterase enzyme in concentrations 120, 120, 200 and 2000 mg/l, respectively in different days after spraying. Most of the inhibition in glutathione S-transferase was observed in spirodiclofen, spinosad, azadirachtin and Thymol spraying soap in concentrations of 180, 240, 200 and 1000 mg/l, respectively. Because of the effectiveness of Thymol spraying soap, its competitiveness with other pesticides, and reduction in production costs (cost-effectiveness) and compatibility with environment, it seems that this insecticide could be a good candidate for psylla control.