Ergot of wheat

Ergot has played an important role in history as it impacts human and animal health. Though less problematic today, the disease can still cause issues, particularly in male-sterile wheat lines. During early infection, some kernels go through a “honeydew” stage where infected ovaries swell and emit a yellow, slime-like fluid. This fluid attracts insects and is full of spores. Ovaries are eventually replaced withhard, dark fungal structures known as sclerotia, which are approximately ½ to ¾ inch long. Sclerotia are characteristic of this disease, developing in place of kernels. Inside, sclerotia are white, cream, or gray colored. The best time to scout is towards the end of the season during flowering and ripening.

Ovaries are eventually replaced with hard, dark fungal structures known as sclerotia. Image: E. Byamukama. 
Sclerotia are characteristic of this disease, developing in place of kernels. Image: A. Friskop. 

Sclerotia survive in or on soil or are introduced with seed. They germinate in spring and release spores which infect wheat flowers. Secondary inoculum can cause additional infections. Cool, moist weather just prior to and during flowering, and other conditions that prolong the flowering period favor disease development. Many grasses serve as hosts and can provide inoculum for wheat crops.

Plant ergot-resistant wheat varieties and avoid planting male-sterile lines in fields where ergot has been problematic. Do not plant bin-run seed and make sure seed is not contaminated with sclerotia. Some fungicide seed treatments may reduce sclerotia viability if planting contaminated seed cannot be avoided. Rotate to a non-grass host to reduce inoculum in a field. Bury residue deeper than 1.5 inches to reduce inoculum for next season, but carefully consider soil health prior to tillage.

Gallery

Gallery images: A. Friskop and E. Byamukama