Skip to main content

Early Season Scouting in Small Grains: Tan Spot

Madeleine Smith, Small Grains and Canola Pathologist

Tan spot lesion.JPG
Tan spot is identifiable by the brown spots often
surrounded by a yellow halo that appear

Having experienced a very late spring as in 2013, we are also experiencing a similar start to the season when it comes to diseases in small grains as last year. Tan spot has made an appearance on wheat and barley around the state.

This may run together to form larger patches of yellowing and browning. Initial infections in young seedlings often result in yellowing of leaf tips as the seedlings react to the toxins produced by this fungus. Tan spot will be particularly prevalent on previous wheat ground. Be careful not to mistake nitrogen deficiency (see recent post to crop e-news by Dr. Jochum Wiersma on early season yellowing in small grains) or symptoms of BYDV for tan spot.

Scouting is really key with these diseases and results in early detection. As tan spot can go through multiple infection cycles in a season, it is important to control it as soon as it is identified. If left unchecked, this disease will continue to progress and may impact yield.

If you do see tan spot, you can use a tank mix of herbicide and fungicide to control this disease. With the young crop, we recommend using half the labeled rate of products containing active ingredients such as propiconazole (e.g. Tilt). This is because there is less biomass at this stage for the fungicide to cover. After application of fungicide, the lesions of tan spot will not disappear, but the fungus in these lesions will have been killed off. It is important to keep scouting new growth in fields to determine if new infections are occurring. If so, an application of fungicide later in the season may be necessary.

A number of different fungicides can be used for control of this disease (follow this link to the current fungicide efficacy table for small grains. ). Always remember to follow current labeling instructions for use.

This year, we are interested in collecting isolates of Tan Spot. So if found, please can you contact me at BEFORE you spray and we will try to collect a sample.
Print Friendly and PDF