COLORADO WHEAT DISEASE NEWSLETTER
DISEASE WATCH AND MANAGEMENT
Stripe rust Stripe rust has been spotted at low incidence and severity across much of Colorado’s wheat growing region (Figure 1). While the weather in Colorado has been conducive to stripe rust disease development, I anticipate that there won’t be a significant disease impact since we are late in the season and the spore levels remain low.
Management and Prevention
The likelihood of getting an economic benefit from a fungicide application drops off quickly after flowering, unless more than 65% of the flag leaf area is covered with rust pustules. Additionally, some fungicides have a postharvest interval (PHI) of 30-45 days, so the window for application closes quickly after flowering. Overall, I don’t think it is economically advantageous for most to spray at this point since rust
Figure 1. Very low levels of stripe rust found during Wheat Field Days.
Wheat Streak Mosaic virus/Triticum Mosaic virus
Wheat streak mosaic virus/Triticum mosaic virus: Several samples have tested positive for WSMV and TriMV (Figure 2). These viruses are transmitted by the wheat curl mite and typically occur together. Symptoms appear as yellow streaks and mosaic, yellow and green patterns on leaves.
Management and prevention
There is no treatment for virus-infected plants, and no miticides are effective against the vector (the wheat curl mite). Controlling volunteer wheat and planting WSMV- and mite-resistant varieties are the best control measures. However, there is no resistance against TriMV available, so controlling volunteer wheat between harvest and planting is critical.
Figure 2. Symptoms of a WSMV and TriMVco-infection.
Growers are strongly encouraged to regularly scout wheat fields for diseases.
The Colorado Wheat Entomology Newsletter, written by Dr. Punya Nachappa, covers insect/mite pests and management tips. The newsletters are published bi-weekly during the growing season.
- The North Central Regional Committee on Management of Small Grain Diseases (NCERA-184) Fungicide Efficacy for Control of Wheat Diseases Table
- Wheat variety database with stripe rust and virus resistance ratings from field trials.
Many thanks to Tyler Benninghoven, Dr. Esten Mason, and Dr. Ana Cristina Fulladolsa, who contributed to this report.