Wheat Disease Ratings Available from Kentucky Variety Test

Bill Bruening — Research Specialist, Lexington

A variety’s susceptibility or resistance to a given pathogen can be directly related to yield, grain quality and profitability. The University of Kentucky Small Grains Variety Testing Program annually evaluates the disease reaction among wheat varieties. The types of disease rated can vary annually depending on which pathogen is active in a given growing season/environment. In 2016, disease ratings were recorded for Stripe Rust, Leaf Rust, Septoria Leaf Blotch, and Powdery Mildew http://www2.ca.uky.edu/agcomm/pubs/PR/PR707/PR707.pdf .

Disease ratings data can be of value in variety selection decisions, but also in terms of disease management decisions during the growing season. No variety is resistant to all diseases, and it is important to know which varieties are susceptible to a particular disease during an unexpected outbreak. For example in 2016, there was a Stripe Rust outbreak in several regions of Kentucky. Stripe Rust is a pathogen that can rapidly destroy the foliage and dramatically affect grain yield. Growers can utilize variety test disease rating data to determine whether to spray or not spray. For example, in the 2016 Kentucky wheat variety test disease ratings, CROPLAN 9201 was rated 8.3 (highly susceptible) to Stripe Rust and a foliar fungicide would likely be essential for areas with reported infection. CROPLAN 9203, on the other hand, was rated 1.7 (very resistant) and a fungicide would likely not be needed for this disease. Stripe Rust has already been reported in Tennessee, Arkansas, Louisiana and Mississippi this year. These observations may be indicative of higher Stripe Rust pressure this year.

The decision to spray fungicide can affect production profitability, certainly in terms of protecting a susceptible variety, but also in terms of savings associated with withholding unneeded fungicide applications and eliminating application costs such as chemical, labor, equipment wear, as well as any environmental effects. With lower wheat yields expected this year due to freeze damage, this is an important economic decision to consider. Results from the University of Kentucky Small Grains Variety Testing program are available online and printed annual reports are available at Kentucky county extension offices.