Population model for the decline of Homalodisca vitripennis (Hemiptera: Cicadellidae) over a ten-year period

The glassy-winged sharpshooter,  Homalodisca vitripennis  (Germar), is an invasive pest which presents a major economic threat to grape industries in California, because it spreads a disease-causing bacterium,  Xylella fastidiosa . In this note we develop a time and temperature dependent mathematical model to analyze aggregate population data for  H. vitripennis  from a 10-year study consisting of biweekly monitoring of  H. vitripennis  populations on unsprayed citrus, during which  H. vitripennis  decreased significantly. This model was fitted to the aggregate  H. vitripennis  time series data using iterative reweighted weighted least squares (IRWLS) with assumed probability distributions for certain parameter values. Results indicate that the  H. vitripennis  model fits the phenological and temperature data reasonably well, but the observed population decrease may possibly be attributed to factors other than the abiotic effect of temperature. A key factor responsible for this decline but not analyzed here could be biotic, for example, potentially parasitism of  H. vitripennis  eggs by  Cosmocomoidea ashmeadi . A biological control program targeting  H. vitripennis  utilizing the mymarid egg parasitoid  Cosmocomoidea  (formerly  Gonatocerus )  ashmeadi  (Girault) is described.