بيولوژي آزمايشگاهي و نوسانات فصلي تريپس توت در استان گيلان (منطقه پسيخان )

The Laboratory Biology and Seasonal occurrence of Mulberry Thrips Pseudodendrothips more Niwa (Thys., Thripidae) in Guilan Province, (Passikhan region)

Mulberry thrips Pseudodendrothr¢ps marl Niwa is an introduced pest of mulberry in Iran. This insect widely attacks both native and hybrid varieties and this lowers the economic value of the leaves consumed by silk- worm. In order to investigate the biology of this pest in laboratory, a culture was established by releasing first and second larval instars on leaves whose petioles were inserted to wet cotton swabs placed inside disposable jars 5.24* 5.5cm. capacity inside an incubator set at 25±ICʹ, relative humidity of 75±5% and photoperiod of 14:10h light- dark respectively. To determine seasonal variations in population of the pest in different generations, sampling was done every five days from first half of May- when wintering adult insect appeared - through the second half of October, when its population declined dramatically. Samplings. were performed in varieties of Shin Ichinoise, Kenmuchi, and Ichinoise, simultaneously. The results indicated that the life- cycle of this insect took 29.95 days from egg to adult in lab condition. The sexual ratio was 6.7:1. The insect overwintered as adults, and had four generations in a year. The highest peak of first larval population in the month of August in Shin Ichinoise were 8.45 and 10.62 in each sample unit, that of Kenmuchi is 9.05 and 12.38 and that of Ichinoise were 5.89 and 16.05 for the years 2000-2001 respectively. The population of second instar and adult were relatively lower in all the generations.