Life table and heat tolerance of Acyrthosiphon pisum (Hemiptera: Aphididae) in subtropical Taiwan

The effect of temperature on the life table of Acyrthosiphon pisum reared on Pisum sativum was evaluated under laboratory conditions using temperatures of 10, 15, 20, 25, 30, and 35 degrees C. The development time of juvenile A. pisum decreased with increasing temperature (from 21.3 days at 10 degrees C to 4.7 days at 35 degrees C). Adult longevity also decreased with increasing temperature (from 53.2 days at 10 degrees C to 2.3 days at 35 degrees C). Interestingly, 70% and 25% of A. pisum nymphs reared at 30 degrees C and 35 degrees C, respectively, successfully developed into adults. These temperatures have previously been considered unsuitable for A. pisum development. However, adult aphids reared at 30 degrees C and 35 degrees C failed to reproduce. Linear regression analysis revealed that the lower development threshold of A. pisum was 153.1 degree-days above 1.9 degrees C. Maximal average reproductive capability was observed at 10 degrees C for A. pisum adults, with each adult producing more than 120 nymphs. The intrinsic rate of increase (r(m)) of A. pisum increased from 0.124/day at 10 degrees C to 0.337/day at 25 degrees C, whereas opposite trends were observed for the net reproductive rate (R-0) and the mean generation time (GT). At 20 degrees C and 25 degrees C, the intrinsic rate of increase of A. pisum was significantly higher than at 10 degrees C and 15 degrees C (P < 0.0001), indicating that 20 degrees C and 25 degrees C are within the optimal range for the growth of A. pisum, and that 30 degrees C is beyond the upper threshold limit for reproduction, which involves a temperature range that is narrower than that of the survival range (upper limit is unknown, but above 35 degrees C).