Seasonal Population Changes of Wheat Green Aphid (Schizaphis graminum) and Introduction of its Natural Enemies in Sistan Region

Seven species of aphids belonging to the family Aphididae in six genera were collected and identified in wheat and barely fields in Sistan region (Miankangi, Shahraki-Narooi, Shibab and Markazi) during1999-2000. Among them, Schizaphis graminum (Wheat green aphid) was the dominant species with an abundance of about 85.4% in the area. The seasonal population changes of Schizaphis graminum were studied simultaneously in the fields of Sistan region (Zahak research station and its surrounding fields). The research was conducted in half a hectar of each farm. Thirty leaves from each field at weekly interval were randomly picked up and the aphids were collected and identified at the species level. The Schizaphis graminum had a peak of activity in the second half of March to April at the temperature and R.H. ranges of between 22-28ºC and %45-65R.H. respectively. The control conditions study (Incubator with 25±2ºC and %75±5R.H.) indicated that the Schizaphis graminum had a life cycle of 5-7 days and adult female longevity was 20-31 days. Rearing study also revealed that this species had ability to reproduce up to 18-98 nymphs in the laboratory condition (Cultural room with 20-25 ºC and 55±5R.H.) and an apterous female gave birth to 22-93 nymphs in her life. Samplings for recognition of predators and parasitoids were also done at 3-day intervals. Natural enemies in the fields during the two years were identified as consisting of six coccinellid (Col:Coccinellidae), ten syrphid (Dip:Syrphidae) and two chrysopid species (Neu: Chrysopidae). Also in Hymenoptera, five parasitoids (Hym:Aphidiidae) were determined.