Survey of Entomopathogenic Fungi Naturally Infecting Cereal Aphids (Homoptera: Aphididae) of Irrigated Grain Crops in Southwestern Idaho

Abstract

A four-year field survey of wheat, barley, and corn generated data on 10 species of fungal pathogens, including eight Entomophthorales and two Hyphomycetes recovered from 2,930 cadavers of aphids infesting grains grown under irrigation in southwestern Idaho. Seven species of cereal aphids, including the Russian wheat aphid, Diuraphis noxia (Mordvilko); the potato aphid, Macrosiphum euphorbiae (Thomas); Metopolophium dirhodum (Walker); the corn leaf aphid, Rhopalosiphum maidis (Fitch); the bird-cherry oat aphid, R. padi (L.); the greenbug, Schizaphis graminum (Rondani); and the English grain aphid, Sitobion avenae (F.), were recorded as hostsof one or more species of entomopathogenic fungi. The fungi were identified as Pandora neoaphidis (Remaudiere & Hennebert) Humber, Conidiobolus obscurus (Hall & Dunn) Remaudiere & Keller, C. coronatus (Costantin), C. thromboides Drechsler, Entomophthora chromaphidis Burger & Swain, Neozygites fresenii (Nowakowski) Remaudiere & Keller, Zoophthora radicans (Brefeld) Batko, Z. occidentalis (Thaxter) Batko, Beauveria bassiana (Balsamo) Vuillemin, and Verticillium lecanii (Zimmermann) Viegas. P. neoaphidis was the most prevalent species annually in populations of M. dirhodum and D. noxia and also frequently infected other hosts. Conidiobolus spp. were secondary to P. neoaphidis in occurrence, commonly infecting several aphid species. E. chromaphidis, N. fresenii, Z. radicans , and Z. occidentalis were recovered only occasionally and on fewer aphid species. Two Hyphomycetes, B. bassiana and V. lecanii , infected aphids in the field at very low levels compared with the Entomophthorales. All species, except N. fresenii and Z. occidentalis , were isolated from their aphid hosts with agar media (SDAY or SEMA, or both) or liquid insect tissue culture medium.