Incidence of Pandora neoaphidis (Remaudière and Hennebert) Humber (Zygomycetes: Entomophthorales) in the Myzus persicae (Sulzer) Complex (Homoptera: Aphididae) on Three Species of Brassica in the Fall and Winter

Abstract

The incidence of the aphid pathogen, Pandora neoaphidis (Remaudière & Hennebert) Humber, was monitored in populations of the Myzus persicae (Sulzer) complex (green peach aphid, M. persicae, and the tobacco aphid, M. nicotianae Blackman) on fall-planted cabbage, spinach-mustard, and turnip from 1993 to 1996. Each fall, the pathogen occurred at moderate levels in M. persicae complex on all three hosts. Average level of mycoses on the three host plants ranged from 10.0 to 14.3% in 1993, from 5.9 to 10.1% in 1994, and from 7.9 to 17.4% in 1995. Each year, the highest incidence of the pathogen in aphids on turnip and spinach-mustard was 20 to 25%, while the incidence on cabbage was 12 to 19%. In 1995 and over the 3 yrs combined, the levels of mycoses were significantly higher (P ≤ 0.05) in aphids on turnip and spinach-mustard than on cabbage. Trends were similar in 1993 and 1994, but differences were not significant. Very low numbers of healthy aphids (<2 per 5 plants in 1994 to 5 aphids per 5 plants in late April 1996) and those infected with or killed by P. neoaphidis occurred on turnip, cabbage, and spinach-mustard from Jan to May. The M. persicae complex was significantly more abundant on cabbage than it was on spinach-mustard or turnip. The pathogen overwinters at very low levels in cadavers of M. persicae complex on Brassica.