Preliminary study on biology and seasonal population dynamics of Turnip Sawfly, Athalia rosae (Hym.: Tenthredinidae), on Canola in Kurdistan province

Increasing of population and outbreak of the turnip sawfly Athalia rosae (Hym.: Tenthredinidae) caused severe damages in many fields of Marivan region in 2001. In this study, biological traits and population dynamics of this pest were investigated in Marivan region during 2004-2005. Results showed that this pest has 3 generations per year and main damage to canola caused by larvae of 3rd generation that its adults emerged in mid of September. The larvae of first and second generations feed on weeds and vegetables in Brassicaceae family. The adult of first generation emerge at early of April and they mate immediately then lay the eggs. Maximum number of laid eggs by one female sawfly in laboratory condition was 57 and mean was 28.2±14. The average developmental periods of egg and larvae were 5.1±0.59 and 17.65± 1.57 days, respectively and the means of pupa stage for females and males were 9.8±1.29 and 12±1.95 days, respectively and total life span was 32-38 days. Average longevity of adult female and male was 9.4±2.24 and 5.7±1.42 days respectively. Sexual ratio (male: female) in the natural condition were 1: 2.68 and 1: 3.03 in 2004 and 2005 respectively. This insect overwinters as final instar larva in a coccon in a few centimeters deep in the soil.