Prevalence ofErynia neoaphidis(Entomophthorales: Entomophthoraceae) Infections of Green Peach Aphid (Homoptera: Aphididae) on Spinach in the Arkansas River Valley

Abstract

Spinach, Spinacia oleracea L., produced for processing in the Arkansas River Valley of western Arkansas was sampled for live and diseased aphids from 1990 to 1993. The green peach aphid, Myzus persicae (Sulzer), was the only aphid detected and its occurrence was highly variable. No aphids were detected in 14 of the24 sampled fields. Nine of the 10 fields in which aphids were detected had individuals infected with the fungus Erynia neoaphidis (Remaudière & Hennebert). No other fungal pathogens were observed. Infected aphids were detected in each of the 3 spinach production seasons (fall, winter, and spring). In several fields, especially during the winter of 1992, aphid populations declined with increased E. neoaphidis incidence. However, in fields with relatively high numbers of aphids this population decline occurred at or after the normal spinach harvest period. Aphids killed by E. neoaphidis were tightly held to spinach foliage and, when epizootics occurred at harvest, the spinach was rejected by the processor due to difficulty in washing the aphid cadavers from the product.