Small Grain Diseases

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Barley
We have had reports of increasing amounts of powdery mildew on barley. Looking at my evaluations of the barley variety trials that Bob Uniatowski conducts yearly, ‘Thoroughbred’ looks to be the most susceptible in the trials but there has never been enough disease present to warrant spraying. Regionally we have no data to evaluate fungicides for control of barley diseases because barley rarely needs to be sprayed for diseases and the cost has been prohibitive. Times have changed and if the heads are emerging and the top two leaves are infected there may be some benefit to controlling powdery mildew on a susceptible variety if the weather continues to favor powdery mildew. Stratego, Tilt, Quilt (10.5- 14.0 oz/A) would be suggested for control if necessary. A beneficial non-target effect will be brighter straw if straw is being baled.

Barley Powdery Mildew

Powdery mildew on barley

Wheat
This week the diagnostic lab received more wheat samples with virus symptoms. The first results have come back and the virus detected was soilborne wheat mosaic virus. SBWMV is a virus that is transmitted to the wheat in the fall by a soil born fungus called Polymyxa graminis. Symptoms range from mild green to prominent yellow leaf mosaics and streaking. Stunting can be moderate to severe. In this region the symptoms are found on plants in areas that are generally wet or poorly drained. Virus symptoms often diminish when the weather gets warm and symptoms are confined to the lower leaves. Symptoms on the upper leaves can look identical to wheat spindle streak mosaic virus. Planting resistant cultivars is the best solution for fields with a history of SBWMV.

I would suggest waiting until early head emergence before applying fungicides to wheat if disease levels do not warrant spraying now. Delaying until head emergence is the last opportunity to apply most fungicides and that application can carry the crop through harvest if glume blotch, tan spot, or rust should appear at or after heading. Another benefit is sooty mold control if we have poor weather during harvest. In most cases disease levels are low in wheat except where high nitrogen carry-over or over fertilization has occurred. That has resulted in more powdery mildew.

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