ISSUE 4 June 4, 2009
TAN SPOT COMMONLY OBSERVED IN WINTER WHEAT PLANTED IN WHEAT STUBBLE IN SOUTHEAST ND
In a survey of some winter wheat and spring wheat fields in Ransom County on June 1, winter wheat fields planted into wheat stubble had good winter survival, but also had considerable amounts of tan spot infections on lower leaves, with some spots also starting to appear on the top two leaves. The spots were very typical of tan spot symptoms, with the dark brown center and noticeable yellow halo around the spot. The winter wheat fields surveyed in this southeast county were in the late jointing to early flag leaf emergence stages. It was too late for early season application of fungicide in these fields, but most will warrant later season fungicide application if rain events continue to occur.
The spring wheat in this county was generally in the 1 ˝ to 3 ˝ leaf stage, and planted into soybean stubble. Tan spot was not observed in these fields.
WHEAT STREAK MOSAIC OBSERVED IN WINTER WHEAT IN SOUTHEAST
Symptoms of wheat streak mosaic virus were observed in all the winter wheat fields surveyed in Ransom County on June 1. The percent of plants showing some level of symptoms ranged from 2% to 20%. Although symptoms were commonly observed, frequency and severity levels in each field were not high enough to warrant any consideration of replanting. The cool weather we are experiencing now favors the wheat crop and its development, and does not favor spread of this disease.
Please see last week’s Crop and Pest Report issue for more information on tan spot and wheat streak mosaic diseases of wheat. NDSU Extension Circulars on these two diseases also are available at:
The Wheat Streak Mosaic circular is numbered PP-626, and the Wheat Fungal Leaf Spot Disease circular is numbered PP-1249.
CEREAL RUST BULLETIN UPDATE
In our survey of winter and spring wheat in Ransom county on June 1, we could not find any symptoms of leaf rust. The Cereal Rust Bulletin’s latest report, dated May 27th, indicates that at that time, low leaf rust levels have been observed on susceptible winter wheat cultivars in south central Kansas, where wheat is moving through the milk stages of kernel development. Lower levels have been observed in that state in north central and west central Kansas. Stripe rust has only been observed at trace levels in Kansas, and no stem rust has been observed.
As of the last week in May, no leaf rust or stem rust had been reported from Nebraska or points north. Oat crown rust was found at low levels in commercial oat fields in Texas. Barley rusts have not been reported in the southern plains states yet, only from Virginia.
Extension Plant Pathologist
DISEASES IN LATE PLANTED PEAS
I have heard concerns about pea diseases due to the late planting. Since this is relatively new territory for me, I have spent significant time talking to my Canadian counterparts about disease pressure, disease management, and late planting. To help in planing for disease management, I have included a few things to keep in mind below. Please keep in mind that environmental conditions can dramatically change disease risk.
Root rots. Disease pressure is likely to be relatively unaffected. Data from last years surveys indicate the we have predominantly Fusarium, and secondarily Rhizoctonia problems in our peas. It is unlikely that pressure will be different based on the delay in planting. However, if we have a dry summer, plants with damaged roots may be prone to suffering more than usual as the season progresses longer and longer.
Foliar Diseases. Don’t jump the gun with early season fungicide applications. Peas have their share of foliar diseases, but I don’t expect an early onset of any of them because of early planting. Further, economic control of foliar diseases has been most commonly shown to occur at the early flowering stage. With adequate rotation, I would expect this to be consistent. Save the fungicide now because there may be an increased chance you need it at early flower. Ascochyta is a constant threat and powdery mildew threatens more as the later the season gets later. Since some peas will be much later this year, an unusual disease occurrence/outbreak later in the season is always possible. It is important to keep your eyes on your crop as the season progresses.
Extension Plant Pathologist