Effects of insect longevity and drought conditions on aster leafhopper (Hemiptera: Cicadellidae) fecundity

Insect population dynamics profoundly affect the potential for a species to serve as a pest, highlighting the importance of proper quantification and monitoring of insect reproduction. Important measurements of reproduction include individual female egg load and realized fecundity, which can be affected by insect longevity and host quality. Aster leafhoppers (Macrosteles quadrilineatus Forbes) are an important pest in Western Canada and the upper Midwest of the United States, yet little is known about factors influencing their fecundity, and thus, population dynamics. To evaluate age-specific changes in fecundity, newly emerged pairs of aster leafhoppers were caged onto plants, and egg and nymph numbers were determined on a weekly basis until females died. Moreover, water deficit can affect amino acid concentrations in phloem sap, and in turn, affect plant attractiveness and suitability for insect herbivores. To examine the relationship between water deficit and reproductive potential, aster leafhoppers were reared on unstressed and water-stressed barley plants until adult emergence. Pairs with all possible combinations of leafhoppers from each water stress condition were made and allowed to reproduce. Amino acid concentrations were quantified in unstressed and water-stressed barley plants. Aster leafhoppers produced eggs throughout their adult stage, with numbers decreasing as individuals got older. Females reared on water-stressed plants had fewer eggs following adult emergence. Following mating, females that had been reared on unstressed plants had a similar egg load to those that had been reared on water-stressed plants. Unstressed plants had a higher concentration of aspartic acid and a lower concentration of tryptophan.