Demography of soybean aphid (Homoptera: Aphididae) at summer temperatures

Soybean aphid, Aphis glycines Matsumura, is now widely established in soybean, Glycine max L., production areas of the northern United States and southern Canada and is becoming an important economic pest. Temperature effect on soybean aphid fecundity and survivorship is not well understood. We determined the optimal temperature for soybean aphid growth and reproduction on soybean under controlled conditions. We constructed life tables for soybean aphid at 20, 25, 30, and 35degreesC with a photoperiod of 16:8 (L:D) h. Population growth rates were greatest at 25degreesC. As temperature increased, net fecundity, gross fecundity, generation time, and life expectancy decreased. The prereproductive period did not differ between 20 and 30degreesC; however, at 30degreesC aphids required more degree-days (base 8.6degreesC) to develop. Nymphs exposed to 35degreesC did not complete development, and all individuals died within 11 d. Reproductive periods were significantly different at all temperatures, with aphids reproducing longer and producing more progeny at 20 and 25degreesC than at 30 or 35degreesC. Using a modification of the nonlinear Logan model, we estimated upper and optimal developmental thresholds to be 34.9 and 27.8degreesC, respectively. At 25degreesC, aphid populations doubled in 1.5 d; at 20 and 30degreesC, populations doubled in 1.9 d.