Temperature effects on life history traits of the corn leaf aphid, Rhopalosiphum maidis (Homoptera: Aphididae) on corn in Taiwan

The effects of temperature on the life history traits of Rhopalosiphum maidis (Fitch) were determined at 6, 10, 15, 20, 25, 30, and 35 +/- 1 degrees C on corn leaves, Zea mays (L.). At 35 degrees C, only a few nymphs survived and completed development, but all failed to reproduce. Total immature stages from birth to adult decreased as temperature increased from 51.7 d at 6 degrees C to 5.2 d at 30 degrees C, but became 8.0 d at 35 degrees C. Overall immature development required 119.05 degree-days above 4.44 degrees C. Adult longevity was as high as 26.7 d at 15 degrees C, but significantly declined at 30 and 35 degrees C. The average adult fecundity was as high as 45 offspring at 15 and 20 degrees C, but dropped to 1.8 at 6 degrees C and 8.6 at 30 degrees C. In general, as temperatures increased, age-specific survivorship (I-x) declined more quickly, but age-specific fecundity (m(x)) peaked earlier. At 25 degrees C, the age-specific net maternity was the highest in the early reproductive period, resulting in the highest intrinsic rates of increase (r(m)=0.329). At 20-30 degrees C, the values of r(m) were significantly higher than those at lower temperatures. The results indicate that corn leaf aphids probably are better adapted in population growth to a wider range of high temperatures in warm regions.