Soybean plant stage and population growth of soybean aphid

The soybean aphid, Aphis glycines Matsumura, is a newly invasive species of aphid in North America. Previous studies disagree as to whether soybean, Glycine max (L.) Merr., plant stage has an impact on aphid intrinsic rate of increase. Therefore, the growth rate of soybean aphids on soybean plants of different stages was examined at two different scales in the field. A planting date experiment was used to measure the population growth of soybean aphids on plants of different stages. Clip-cages were used to measure life history characteristics of individual aphids on plants of different stages. No differences were found in the population growth or dynamics of soybean aphids in the planting date experiment. The life history characteristics of individual aphids also showed no significant difference when feeding on different growth stages of soybean plants. The impact of these findings on soybean aphid management is discussed and the possible reasons why the results differ from previous estimates of the aphid growth-plant stage relationship are considered.