Influence of temperature-driven phenology and photoperiodic induction of reproductive diapause on population dynamics of Erythroneura comes (Homoptera: Cicadellidae)
Martinson, T.E. | Dennehy, T.J.
The influence of degree-day accumulations and photoperiodic induction of diapause on the phenology of Erythroneura comes (Say) was investigated. In growth chamber experiments, nymphs reared at photoperiods of < 13.5:10.5 (L:D) h entered reproductive diapause. Egg production and proportions of gravid females in field populations dropped sharply between 1 and 15 August in both the warm (1991) and cool (1992) growing seasons, suggesting that the onset of reproductive diapause occurs in late July to early August. Stage-specific developmental times from a 1912 study of 118 leafhopper nymphs were used to estimate degree-day requirements (base 10 degrees C) for eggs and the 5 nymphal stadia. These estimates were used to construct a stage-specific developmental model, which was validated with field data collected at 4 vineyards in 1991 and 1992. The model predictions agreed well with the timing of developmental events in 4 vineyards in both 1991 and 1992, years representing extremes in temperature accumulations in western and central New York. These data suggest that accumulations of > 710 degree days (DD) before 1 August are required to produce a 2nd generation of E. comes under climatic conditions in New York. Variations in temperature-driven development are hypothesized to strongly influence year-to-year variability in leafhopper abundance. Degree-day accumulations by 30 June correlated well with degree-days by 1 August and may provide a useful early-warning system for predicting years in which leafhopper population densities are above average.
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