حساسیت جمعیت‌های مختلف پسیل پسته Agonoscena pistaciae به حشره‌کش اسپیروتترامات و تعیین برخی ویژگی‌های مقاومت

Common pistachio psylla, Agonoscena pistaciae is a major pest of pistachio trees in Iran. Feeding the pest from plant sap led to producing a lot of honeydew and falling leaves and buds, severe weakness of trees and reduced quantity and quality of yield. Since past years, insecticides have been widely using to control pistachio psyllid in Iran. Due to biological properties of this pest such as high production rate and several generations in a year, a high potential for resistance to insecticides can be expected. The aim of present study was to investigate the resistance status of some Iranian populations of pistachio psylla to spirotetramat. In trials, eight populations were collected from major pistachio cultivation areas Kerman (Zarand, Sirjan and Rafsanjan) Yazd (Abarkooh and Mehriz) and Khorasan Razavi (Torbate Jam, Fayzabad and Bardaskan) which had been under heavy insecticides applications. A susceptible population without any insecticide application history was also collected from wild pistachio species (Pistacia atlantica var mutica). Dose–mortality lines were constructed based on F1-F3 generation of these populations in the laboratory. Susceptibility of the second instar nymphs to insecticides was evaluated using a special leaf dip bioassay method. Terminal part of the plant with infested leaves were dipped in insecticide solution. Resistance selection and reversion were also investigated in laboratory with and without spirotetramat selection pressure. Cross-resistance pattern in spirotetramat-resistant strain was assessed by using different insecticides from various chemical group. Synergistic effect of PBO, DEF, DEM on the resistant strain was evaluated. Synergists were also treated using same leaf deep method. The nymph were treated by synergist 4 hours before the insecticide treatment. The resistance ratio was calculated through dividing the LC50 of each population to its own susceptible population. According to the results the susceptible strain at LC50 level, resistant ratios to spirotetramat in Zarand, Mehriz, Fayzabad, Rafsenajn, Torbate Jam, Bardaskan, Abarkooh and Sirajan were 55.4, 22.4, 18, 13.8, 12.5, 7. 4, 2.6 and 2.1 fold, respectively. In laboratory selection pressure in susceptible strain, the resistance level to spirotetramat increased considerably to 255 fold after 44 generations while in Zarand Strain it increased to 672 fold after 32 generations. However, in these population resistance level decreased down to 6 fold after 20 generation when it was not any insecticide pressure. Spirotetramat resistant strain showed cross resistance to abamectin, deltamethrin, permethrin, lambda-cyhalothrin and phosalon while it was not recorded in other applied insecticides (such as neonicotinoids, sulfur, azadirachtin, flupyradifurone). In synergistic studies, PBO reduced resistance level about 3.6 times. In conclusion, as this pest has a high potential for resistance to insecticides, it is required to apply resistance management strategies for reducing development of resistance as much as possible.