Pathogenic fungi associated with Fusarium foot rot of winter wheat in the semiarid Pacific Northwest.
Winter wheat plants and soil were collected from 288 nonirrigated fields in the semiarid Pacific Northwest, USA, during 1993-94. Fungi associated with 5390 crown and subcrown internodes, from 10 Oregon and 9 Washington counties were identified. F. graminearum [Gibberella zeae] Group I was the most prevalent pathogen associated with crown and root rot. F. culmorum was widely distributed in soil but was only detected in plants in half as many locations as G. zeae. Other pathogens included Bipolaris sorokiniana [Cochliobolus sativus], Microdochium nivale [Monographella nivalis] and F. avenaceum [G. avenacea]. Highly variable isolation frequencies for all 5 pathogens were presumed to be related to environmental conditions. Each pathogen was considered dominant or co-dominant at 1 or more sites during 1 or more years. Isolates from all 5 species and F. acuminatum [G. acuminata] and F. oxysporum killed wheat seedlings in the greenhouse.