Loose smut of wheat

Loose smut has a wide distribution and can occur anywhere wheat is produced. It is caused by the fungus Ustilago triticiMild symptoms may be present prior to heading, including yellowish leaf streaks and stiff, dark green leaves. Affected plants head out early, producing sterile heads with clumped, sooty olive-black spores in place of healthy glumes and kernels. Spores are not enclosed by the seed coat, so are quickly dispersed by rain or wind after emergence. After spores disperse, only a bare rachis remains with a few fragments of glumes or awns. These spores infect other wheat plants at flowering, causing seed infection. Infected seed appear healthy. The best time to scout is after heading.

Affected plants head out early, producing sterile heads with clumped, sooty olive-black spores in place of healthy glumes and kernels. Image: C. Grau. 
Spores are not enclosed by the seed coat, so are quickly dispersed by rain or wind and only a bare rachis remains with a few fragments of glumes or awns. Image: A. Friskop. 

The fungus is seedborne, and unless infected seed is planted, no disease will occur in a field. New infections are favored by humid, cool weather 60-72°F during flowering (FGS 10.5.1 – 10.5.3).

Less susceptible varieties of wheat are available. Plant certified seed to reduce disease risk. Do not save seed from fields with loose smut. Fungicide seed treatments can effectively manage loose smut.

Gallery

Gallery images: C. Grau and A. Friskop.