بررسي تغييرات جمعيت زنبور TRIOXYS PALLIDUS پارازيتوييد شته سبز گردو در استان قزوين

Population changes of Trioxys pallidus, a parasitoid of walnut aphid in Qazvin province.

Trioxys pallidus (Hall.) is one of the most important natural enemies of walnut aphids in almost all walnut orchards. Unfortunately in recent years, insecticide spraying as a common pest control measure in walnut orchards, has had negative impacts on this parasitoid population. In order to study the population changes, emerging time, flight peak and comparing population, weekly sampling procedures was carried out in walnut orchards located in the uplands as well as plain areas of Qazvin. In each orchard, eight trees and in each tree seven leaves of different directions were randomly selected. The leaves carrying mummy aphids were collected and after counting were maintained in petri-dishes until the wasps emergence. Hyperparasites were ignored during counting and only member of T. pallidus were recorded. Results showed significant difference between populations in two areas using T-test method. The first aphids were observed in mid-April in lowland areas and in early-May for the mountains. Sampling continued until the end of October. The wasps passed the summer in diapause phase. In late September the diapause in some wasps in petri-dishes was broken but mostly remained in diapause.