Wheat Disease Update – June 1, 2016
Written by: Kirk Broders, Plant Pathologist; Department of Bioagricultural Sciences and Pest Management, Colorado State University; C030 Plant Science Bldg., 1177 Campus Delivery, Fort Collins, CO, 80523-1177; 970-491-0850 (work); firstname.lastname@example.org
The wheat in Colorado is progressing quite well, the cool weather has slowed growth modestly, but overall much of the wheat is between Feekes Growth Stage 10 – 10.5. The cool wet weather has provided good growing conditions for the wheat and growers should see good yield across the state. However, these same weather conditions are favorable for a number of foliar pathogens. In particular stripe rust is widespread across the state but disease severity is generally low in most areas. This is likely due to the fact that many growers applied a fungicide at flag leaf. The main concern now will be the longevity of the fungicide in the leaf and its ability to prevent further infection. Hopefully the forecasted warmer and drier weather in the next week will also help slow down the sporulation and spread of the pathogen.
In addition to stripe rust, I have received reports of bacterial streak, Stagonospora leaf and glume blotch and powdery in several fields in the eastern part of the state. These diseases are not wide spread, but could increase in the coming weeks depending on the weather. There has also been a significant amount of virus (Wheat streak mosaic & Barley yellow dwarf) pressure in certain parts of the state, and this is usually associated with when and where the crop was planted last fall. Early planting in close proximity to corn and/or volunteer wheat provides the greatest risk of virus infection in the subsequent year.
Reports from other states: Besides the reports I am providing below, the stripe rust situation throughout the central plains and eastern U.S. has become quite severe with reports from nearly all the wheat growing states in the central and eastern U.S. In many states produces are facing the dilemma of a flag leaf fungicide application followed by a later application at flowering to prevent fusarium head blight infection.
Oklahoma: Bob Hunger, Extension Wheat Pathologist, Oklahoma State University
This likely will be my last OK disease update for a while as diseases have mostly “run their course” in Oklahoma and harvest has started. However, I wanted to provide a follow-up on the late season root rots we saw at several locations across northern Oklahoma. Symptoms and a description of the setting in the field all pointed to take-all in several of the samples, and Jen Olson in the Diagnostic Lab and I did find visual signs of the take-all fungus. With further examination, Jen found lesions indicative of Rhizoctonia root rot, and subsequently, she isolated Rhizoctonia. In another sample with whiteheads that to me appeared to be take all, Jen isolated Parastagonospora nodorum and Fusarium (most likelyacuminatum as indicated by DNA sequencing). In a third sample in which roots appeared clean but the lower stems were discolored, Jen isolated Rhizoctonia, but also more commonlyFusarium (again most likely acuminatum), Curvularia, and Parastagonospora. Likely some of these were secondary. So, the exact cause of the whiteheads is somewhat uncertain with Rhizoctonia root rot, take-all, and perhaps some Fusarium-induced root rot all involved.
North Dakota: Dr. Andrew Friskop (Ast Professor/Cereal Extn Pathologist); North Dakota State University; May 23, 2016: “Stripe rust was confirmed in two counties in North Dakota on May 23. One sample was from a winter wheat research plot near Fargo (Cass County), and the other was from a winter wheat variety performance trial in southwest ND near Hettinger (Adams Co.). This is approximately 10 days ahead of when stripe rust was detected in North Dakota last year. Given the susceptibility in popular spring wheat and winter wheat varieties, growers will be encouraged to scout especially with rain and dew in the forecast.”
Ohio: Dr. Pierce Paul (Assoc. Professor); Ohio State University; May 24, 2016: “Stripe rust continues to spread across the state of Ohio. This is the most widespread and the earliest I have seen this disease in the state in 13 years. Several varieties in fields south of interstate 70 and west of interstate 71 are severely affected, with substantial damage to the flag leaf well before flowering in multiple hot spots in some field. As we approach flowering in more northern counties, the reports continue to come in. Several fields have already been sprayed for stripe rust, but the dilemma facing most growers is whether to spray for stripe rust or wait to spray for scab in fields not yet at anthesis.”
South Dakota: Dr. Emmanuel Byamukama (Ast Professor/Extn Spec – Plant Pathology); South Dakota State University; May 27, 2016: “I scouted several winter wheat fields this week in East (Codington, Clark) , Central (Beadle, Hyde, Hand, Hughes) and West (Stanley, Jackson, Pennington) South Dakota and I found stripe rust in almost every field I scouted. The majority of these fields have stripe rust just starting while a few have moderate to severe stripe rust. Winter wheat is beginning to head and a few fields are at flowering. With more rain in the forecast, a fungicide may be necessary to manage stripe rust. The challenge is going to be needing another fungicide shortly for scab management. And with the wheat prices not encouraging, producers are concerned applying 2-3 fungicides in winter wheat this season.”
Kirk D. Broders, PhD
Department of Bioagricultural Sciences and Pest Management
Colorado State University
Submitted to BARN Media by:
Dr. Wilma Trujillo