FUNGAL PATHOGENS BNFICTING SOYBEAN APHID AND APHSDS ON OTHER CROPS GROWN IN SOYBEAN OF MICHIGAN

摘要

Seasonal prevalence of fungal pathogens infecting soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), was assessed from 2004 to 2006 in two Michigan soybean production areas. In 2005 and 2006 field-collected soybean aphids were incubated,and fungal infection was detected at both sites early in August 2005 during soybean pod development and high soybean aphid densities. Significantly higher proportions of winged aphid morphs were infected (20 and 90% infection at the two sites) than wingless aphid morphs (1 and 3% infection). All cases of mycosis examined involved one pathogen species, Pandora neoaphidis (Remaudiere & Hennebert) Humber (Entomophthorales: Entomophthoraceae). In 2004 and 2005, we surveyed for pathogens of the soybean aphidin soybean as well as pathogens in other aphid species feeding on other crop plants (alfalfa, clover, corn, and wheat) by inspecting for sporulating aphid cadavers every 2 to 3 wk during the soybean growing season. Aphid cadavers were most abundant in alfalfa, especially in August; were less common in clover, corn, and soybean; and were not found in wheat. Pandora neoaphidis was associated with cadavers of Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae) in alfalfa and clover during the same periodwhen soybean aphid infection was detected. Overall, mortality of soybean aphid and other aphid species due to fungal infection was confirmed in Michigan. The results also implicate infected winged soybean aphid morphs as potential agents for fungal dispersal, and A. pisum in alfalfa and clover as a source of fungal propagules for soybean aphid.