Effects of Different Temperatures on Biological Parameters of Cabbage Aphid,Brevicoryne brassicae (Hom., Aphididae)

The biological parameters of cabbage aphid, Brevicoryne brassicae (L.) was studied in the laboratory conditions under the three constant temperatures (20, 25 and 30 ºC), RH 60±5% and a photoperiod of 16:8 (L:D) using 40 first instar nymphs. Among nymphs, 40%, 55% and 10% of them completed their nymphal period in 20, 25 and 30 ºC, respectively and developed to adult stage. In 30 ºC, the most biological acitivities of aphid were disrupted and the most individuals (nymphs and adults) were killed. Most developmental periods, longevity and the amount of reproduction in 20 ºC were significantly greater than other temperatures. In temperatures 20, 25 and 30 ºC the last individual of a cohort died in age of 33, 29 and 16 days, respectively. The life expectancy of cabbage aphid in the first day of experiment was 13.93, 10.50 and 7.19, respectively according to the mentioned temperatures. There was a little difference between net reproduction rates in temperatures 20 and 25 ºC (16.74 and 15.92, respectively). Net reproduction rate was reduced extremely in temperature 30 ºC (1.75). The intrinsic rate of the increase in the temperatures 20, 25 and 30 ºC were 0.187, 0.226 and 0.042, respectively. The results indicated that 25 ºC was the optimal temperature for biological activities of B. brassicae and its highest population growth was observed at this temperature.