زيست شناسي و تغييرات فصلي جمعيت سوسك سرشاخه خوار پسته در اصفهان

Biology and Seasonal Occurrence of Pistachio Twig Borer,Hylesinus vestitus Rey.(Coleoptera; Scolytidae)

Pistachio twig borer, Hylesinus vestitus Rey, is an important pest of pistachio trees that causes injury with feeding in buds and twigs and its final damage is yield loss. Biological studies were conducted in two non - commercial infested orchards in Isfahan province. To determine appearance, peak and end of activities in different life stages, 20 infested branches with 25-30 cm of length and 2-3 cm in diameter were weekly collected from each orchard. In laboratory, bark of these branches was removed and number of eggs, larvae, pupae and adult beetles were recorded. In growing seasons, with inspection of buds on 10 randomly selected trees (5 branches per tree) in each orchard, starting, peak and terminating date of attack to the buds, was determined. Sex ratio was determined and natural enemies collected. The first adults emerged from buds in October, gradually continuing until mid-April. Emerged adults attacked the weak branches. Two distinct oviposition peaks occurred in early November and late March of the next year respectively. Following, two peaks of larval densities in late November and mid-April, but only one pupal peak was observed in early May. New adults emerged initially from weak branches late April and attacked to buds. Attack peak the buds occurred in mid-May and then gradually declined through late May, thereafter no more attack to buds being observed. The results revealed that this pest is an univoltine that overwinters in egg, larval and adult stages. Five natural enemies were collected.