Stripe rust or yellow rust is caused by the pathogen Puccinia striiformis f. sp. tritici. Stripe rust is a cool-season disease. Temperatures between 50-64°F (10-18°C) and intermittent rain or dew events are optimal for disease.
Stripe rust has become a perennial and serious problem in the southern plains. Every so often it makes it into the northern plains early enough in the season to cause a problem in Minnesota. A good overview of the disease, including excellent pictures, can be found here.
The last serious outbreak in Minnesota was in 2015. This year the disease has already made it as far north as Brookings. The current weather conditions are favorable for stripe rust to take hold.
Unfortunately, the intermittent outbreaks mean that we have few resistance ratings on the spring wheat varieties that are currently grown. That means that you have to scout to figure out whether stripe rust is developing in your crop.
If you find strip rust and have not applied herbicide add a fungicide to your tank mix. If you have already completed weed control, continue to monitor the field.
The next most economical fungicide application timing will be when the flag leaf is fully extended. However, if your variety turns out to be very susceptible and the disease progresses toward the top of the canopy faster than the canopy develops you may have to intervene sooner.
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