COLORADO WHEAT DISEASE NEWSLETTER
June 6, 2022
Reports of mosaic virus symptoms have increased this past week, with moderate levels reported in symptomatic fields. All of the samples we have tested so far this year have been positive for both Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) (Figure 1). In WSMV-resistant varieties, WSMV levels have been low, so the symptoms observed in these varieties are very likely caused primarily by TriMV. However, in susceptible varieties, both WSMV and TriMV levels have been very high. This suggests that the WSMV resistance is still working in WSMV-resistant PlainsGold® varieties, but we will continue to monitor for resistance-breaking. The drought has contributed to the severe virus disease symptoms this year.
I will attend Wheat Field Days on Monday and Tuesday next week (6/12 and 6/13, Roggen, Julesburg, Yuma, and Akron). If you would like disease diagnostic assistance, please send me an email email@example.com. I am happy to look at samples at the Field Days and can give you instructions on the best way to sample.
Figure 1. Mosaic virus symptoms in southwest Nebraska (photo: Tyler Benninghoven).
DISEASE WATCH AND MANAGEMENT
There are still no reports of stripe rust in Colorado, and I expect stripe rust pressure to remain low. However, keep an eye out for disease and please let me know if you think you see stripe rust.
Watch for mosaic viruses, especially in stressed fields. Feel free to send me photos if you think your field is showing virus symptoms.
Growers are strongly encouraged to regularly scout wheat fields for diseases. Particularly, scout for stripe rust and viruses in the coming weeks.
The Colorado Wheat Entomology Newsletter
Written by Dr. Punya Nachappa and Darren Cockrell, covers insect/mite pests and management tips. The newsletters are published bi-weekly during the growing season and are available here: https://coloradowheat.org/category/news-events/wheat-pest-and-disease-update/
1. Information about the ‘green bridge’ and risks for viral diseases due to volunteer wheat: https://eupdate.agronomy.ksu.edu/article_new/spring-emerged-volunteer-wheat-should-producers-worry-about-wheat-streak-mosaic-virus-and-the-green-bridge-436-4
2. The North Central Regional Committee on Management of Small Grain Diseases (NCERA-184) Fungicide Efficacy for Control of Wheat Diseases Table: https://crop-protection-network.s3.amazonaws.com/publications/fungicide-efficacy-for-control-of-wheat-diseases-filename-2021-04-21-154024.pdf
3. Wheat variety database with stripe rust resistance ratings from field trials: https://wheat.agsci.colostate.edu/database/
4. ‘Making Better Decisions’ 2021 Colorado Wheat Field Days publication: https://webdoc.agsci.colostate.edu/csucrops/reports/winterwheat/wheatreport_2021_WFD.pdf
Many thanks to all who contributed to this report: Tyler Benninghoven, Dr. Esten Mason, Emily Hudson-Arns, Ron Meyer, and Dr. Todd Ballard.