The use of cohorts to evaluate the impact of encarsia citrina (Hymenoptera: Aphelinidae) on Fiorinia externa (Hemiptera: Diaspididae) in the Eastern United States

Abstract

Two years of natural enemy exclusion experiments with cohorts of the invasive scale Fiorinia externa Ferris were conducted in Connecticut, Pennsylvania, and North Carolina. The parasitoid Encarsia citrina Craw had a significant effect on the percentage of F. externa that reached reproductive maturity. For cohorts exposed to E. citrina, 11% reached maturity in 2006 and 8% in 2007 compared to cohorts protected from E. citrina, in which 29% reached maturity in 2006 and 18% in 2007 (averaged across all 3 states). While E. citrina exerted some control of F. externa density, it was insufficient to maintain F. externa density at the study sites at levels comparable to those of the scale in its native range in Japan.