POPULATION-DYNAMICS AND DIURNAL ACTIVITY OF POTATO LEAFHOPPER (HOMOPTERA, CICADELLIDAE) IN CENTRAL IOWA ALFALFA

Studies were conducted in Iowa from 1994 through 1996 to assess the po pulation dynamics and diurnal activity of potato leafhopper, Empoasca fabae (Harris), in alfalfa. The population dynamics study showed that potato leafhopper populations can reach economic levels in each of the three alfalfa crops during a growning season. However, economic thres holds were consistently exceeded only in the second alfalfa crop. In t he second crop, current economic thresholds were exceeded approximatel y 3 weeks after first harvest. Potato leafhopper adults were collected in each of the three alfalfa crops, but nymphs were only collected in the second and third crops. The diurnal study showed that there were significant differences in the number of leafhoppers captured at diffe rent times of the day 66% of the time. However, there were no consiste nt trends in the relative number of leafhoppers captured at a particul ar time. For samples collected around 1000 h or at 1900 h or later, pr esent economic thresholds may be too low. But there was not enough con clusive evidence from this study to justify development of different e conomic thresholds based on the time of day leafhoppers are sampled.