Potato Leafhopper (Homoptera: Cicadellidae) Immature Development, Life Tables, and Population Dynamics under Fluctuating Temperature Regimes

Abstract

Life table studies were conducted with potato leafhopper, Empoasca fabae (Harris), cohorts at three fluctuating temperature regimes. Combinations of daily low and high temperatures for the three regimes were 13 to 24, 18 to 29, and 23 to 34°C. Estimated temperature threshold for immature (egg plus nymph) development was 8.4°C. Temperature had a marked effect on natality and mortality schedules and on life table statistics of the three cohorts. Gross and net reproductive rates were largest at the regime with lowest temperatures. When computed on a day scale, intrinsic and finite rates of increase were largest, and mean generation time shortest, at the regime with highest temperatures. Values of the latter three life table statistics converged somewhat but not completely when computed on a degree-day (above 8.4°C) scale. This failure to converge was due to substantial differences in age-specific mortality on a degree-day scale among the three cohorts. Compositions of the stable stage distribution were similar for the three cohorts. Computer simulations with a Leslie matrix model suggested that, for potato leafhopper populations that are initiated by reproductive females in a given environment, the realized population growth rate will be similar to the intrinsic rate of increase for that environment, and furthermore that the realized growth rate will not be greatly influenced by large fluctuations in population stage structure.