Population Dynamics and Distribution of Aphid Species on Head Lettuce in the Yuma Valley

Abstract

Studies were conducted in the 1999/2000 growing season to examine the population dynamics and field distribution of aphid species on winter and spring head lettuce crops. Seven, 0.25 acre planting of head lettuce were established beginning in October with final harvest occurring in April. Plant samples were conducted weekly to estimate the numbers of both alate (winged) and apterous (wingless) green peach aphids, potato aphids, cowpea aphids and lettuce aphids. Lettuce aphids were more abundant this spring than anticipated, which may indicate that lettuce aphid may be a new pest for Yuma growers. However, based on a single years data, it is difficult to measure the threat that this aphid poses to the lettuce industry. Planting date and temperature likely has a strong influence on seasonal abundance of lettuce aphids. Similarly, the consistent appearance of cowpea aphids during the season was surprising , considering that it has seldom been observed on desert lettuce. Perhaps most surprising though was the low population abundance of green peach and potato aphids in out plots. Part of this unusual event may be due to the unseasonably warm, dry growing season that was experienced this year.