[Effects of temperature on population parameters of Therioaphis trifolii (Monell) (Homoptera: Aphididae)]

To investigate the effects of temperature on the population growth of Therioaphis trifolii (Monell) (Homoptera: Aphididae), a laboratory experiment was conducted to study the development, reproduction, and life table of the spotted alfalfa aphid at nine constant temperatures ranged from 15 to 35 degrees C. The aphid could not survive at 35 degrees C. The total nymphal period shortened significantly with increasing temperature. From birth to adult stage, it required 18.33 days at 15 degrees C, but only 4.02 days at 32 degrees C. The survivorship of the nymphs ranged from 40.0% (32 degrees C) to 83.6% (25 degrees C). The average longevity of the adults ranged from 10.64 days at 32 degrees C to 20.87 days at 23 degrees C. The reproductive peak was advanced with increasing temperature, and the reproduction duration at all test temperatures was 3-6 days except that at 15 degrees C (15 days). The average fecundity and the highest fecundity were the highest at 25 degrees C, being 82.0 and 149.0 offspring per female aphid, respectively. When the temperature increased, the mean generation time was gradually decreased from 31.17 days at 15 degrees C to 10.17 days at 32 degrees C. The net reproductive rate was the highest (68.62) at 25 degrees C and the lowest (13.96) at 32 degrees C. The intrinsic rate of increase was 0.10-0.30 per day, with the highest at 28 degrees C but the lowest at 15 degrees C. The developmental threshold temperature and thermal constant of the nymphs were 9.35 degrees C and 97.83 day-degrees, respectively. Unary quadratic equation could be used to describe the relationships of the fecundity, net reproductive rate, and intrinsic growth rate with the temperature.