The efficiency of diatomaceous earth and silica in decline of eggs and adults of Agonoscena pistaciae (Hem., Psyllidae)

Pistachio psylla, Agonoscena pistaciae Burckharat & Lauterer (Hem., Psyllidae), is the most important pest of pistachio orchards in Iran. It causes to reduce the quantity and quality of the product. Nowadays, because of environmental side effects, resistance development and residues in human food the application of safe insecticides was increased in order to reduce the use of chemical insecticides. Therefore, the effect of two mineral powders was studied including diatomaceous earth and silica on A. pistaciae in the field experiment. The factorial experiment with a randomized complete block design including two types of compounds with three concentrations and six sampling times were used in the crop year 2019. Treatments were included three concentrations of diatomaceous earth (4, 6 and 8 per thousand) and two concentrations of silica (4 and 8 per thousand) and control treatment (water without mineral powders) were sprayed over the whole tree canopy. The total number of eggs and adults were counted 3, 8, 13, 18, 21 and 28 days after treatment on the randomly collected leaves. All of treatments and sampling dates were significantly different on egg of A. pistaciae and diatomaceous earth 6 per thousand (+Dimethicone) and 8 per thousand were the most efficient on the means number of eggs during 8 to 13 days after treatment. While in adult stage only 3 and 8 days after treatment significant difference was observed between treatments and two previously effective treatments on eggs, had most effect in adults reduction in the means number of adults per leaf, during  18 to 23 days after treatment. Based on this study, different concentrations of diatomaceous earth were the most effective on eggs and adults.