Is a fungicide necessary to manage winter wheat diseases this fall?

Farm Forum

BROOKINGS, S.D. — A few cases of stripe rust, powdery mildew and tan spot have been reported in winter wheat this fall.

“Producers are wondering if it is worthwhile to apply a fungicide to control these fungal diseases,” said Emmanuel Byamukama, Assistant Professor & SDSU Extension Plant Pathologist.

Growers need to consider a few factors before answering this question explained Byamukama.

Byamukama outlines those factors below:

A fungicide is applied mainly as a protectant to prevent new infections from taking place and also to limit further inoculum development.

This ensures that the leaves maintain their capacity to carry out photosynthesis.

However, for winter wheat in fall, leaves will soon die from freezing temperatures and therefore applying a fungicide may not be beneficial.

In cases where winter wheat seedlings (2-3 leaf stage) are found with stripe rust and other fungal diseases, and warm fall weather (at least two weeks) is still in the forecast, a fungicide application may be necessary to help wheat plants establish well before vernalization.

However, fields, where fungal diseases are being found in the fall, should be scouted early in spring. If these diseases are found on lower leaves early in spring, an early fungicide application at the herbicide timing may be needed.

Stripe Rust Development and Spread: Stripe rust is one the three cereal rusts that infect wheat and can result in severe yield losses.

“The last two years have seen severe development of stripe rust promoted by wet and cooler (less than 65 degree Fahrenheit) spring weather,” said Byamukama.

In mild winters or when snow cover provides insulation, stripe rust pathogen can survive on fall-infected leaves. In bitter cold winters, stripe rust inoculum does not overwinter in South Dakota but blows up from the Southern states on the northerly winds in the spring.

The other fungal diseases common in wheat, such as tan spot and powdery mildew, are residue-borne and are quite common, especially in wheat planted into wheat stubble.