Economic significance of take-all on winter wheat in the pacific northwest USA

Abstract

The economic significance of take-all of winter wheat, caused by Gaeumannomyces graminis var. tritici, was estimated for Idaho, Oregon, and Washington. Questionnaires were mailed in 1984 to ∼ 3500 producers, of which 1000 were returned and usable. Final estimation considered only fields that received 45 cm or more of moisture through precipitation (or irrigation), and those with winter wheat grown in high-risk rotations, i.e. wheat grown at least 2 of every 3 years or rotated with barley. The survey information revealed that 250 000 ha (640 000 acres) or ∼ 13% of the region's total 1983 planted winter wheat hectarage was affected by take-all. The effect of take-all on yield was estimated in two experiments. Fumigated plots (‘pathogen free’) were interspersed with non-fumigated plots, and regression analysis was used to relate take-all severity in May (early heading) with final grain yield. There were no other pathogens at a significant level in the test plots that would have affected the yields. Take-all was relatively mild in both fields, yet coefficients of determination ( R 2) were both significant (0.71 and 0.39, respectively). The actual (average) field-wide yield was estimated to be only 75–85% of the attainable yield of 7000 kg ha −1) (104 bushels acre −1) in the absence of take-all. Given an average yield reduction of 20% in fields receiving at least 45 cm of moisture from both precipitation and irrigation, it is estimated that in 1983, the Pacific Northwest states could have produced an additional 350 000 t wheat with take-all control and the same input of water, fertilizer, and land.