Enhancing biotic mortality of the potato leafhopper, Empoasca fabae
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This dissertation quantified the population dynamics of E. fabae and developed a new management technique for this alfalfa pest. A two-year study monitored the number of E. fabae at 3 locations within alfalfa fields from mid-April to June and from adjacent tree/shrub species until July. Similar numbers of E. fabae were present on all tree and shrub species. There were more E. fabae at the edges of the fields closest to the trees than at 40 m into the field during the 1st week of May. In subsequent samples, there was no difference in the distribution of E. fabae in the alfalfa field. Based on this study, E. fabae are not using adjacent trees to build up population numbers to infest nearby alfalfa fields in early spring.;The effects of a 3 m uncut strip at first harvest on the distribution of E. fabae and predatory species in alfalfa were examined from 1998 to 2000. Higher numbers of E. fabae were observed in the uncut strips than in the regrowth for 2--3 weeks after harvest in 2 of 3 years. The number of insect predators within the uncut strip was higher during the second week after harvest. This research provides alfalfa growers a potential cultural management technique for E. fabae while retaining beneficial insects.;Predation rates of E. fabae by four predatory species were examined in a greenhouse study. Adult Coleomegilla maculata and Orius insidiosus consumed more E. fabae nymphs than adults. In contrast, similar numbers of adult and nymphal E. fabae were consumed by Nabis roseipennis and Chrysoperla carnea.;Adults and nymphs of E. fabae and adults of predatory species were sampled in Iowa alfalfa fields from June--September in 1999 and 2000. Partial life tables were constructed for E. fabae nymphs. For the 1st growing period, E. fabae nymphal mortality was 70% and 49% in 1999 and 2000, respectively. During the last growing period, total nymphal mortality was relatively low (<25%) in both years.