Evaluation of the Ryegrass Stem Rust Model STEMRUST_G and Its Implementation as a Decision Aid.

STEMRUST_G, a simulation model for epidemics of stem rust in perennial ryegrass grown to maturity as a seed crop, was validated for use as a heuristic tool and as a decision aid for disease management with fungicides. Multistage validation had been used in model creation by incorporating previously validated submodels for infection, latent period duration, sporulation, fungicide effects, and plant growth. Validation of the complete model was by comparison of model output with observed disease severities in 35 epidemics at nine location-years in the Pacific Northwest of the United States.

Quantitative Assessment of Anguina sp. and Rathayibacter rathayi in Dactylis glomerata Seed Production Fields in Oregon and Estimates of Yield Loss.

Anguina sp. is a nematode that infests the inflorescence of orchardgrass and forms galls that replace the seed. Anguina sp.

First Report of Choke, Caused by Epichloe typhina, on Orchardgrass in Oregon.

During July 1997, Epichloe typhina (Pers.:Fr.) Tul.