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Entomology and Plant Pathology, Oklahoma State University 127 Noble Research Center, Stillwater, OK74078 405.744.5527 Vol. 11, No. 24 http://entoplp.okstate.edu/Pddl/ May 4, 2012 Wheat Disease Update Bob Hunger, Extension Wheat Pathologist This past week I and Dr. Jeff Edwards (OSU Small Grains Extension Agronomist) were at several field days and visited numerous fields across central Oklahoma ranging from Stillwater to Marshall (30 miles west of Stillwater) to south of El Reno (15 miles west of Oklahoma City) to Kingfisher (20 miles north of El Reno) to Homestead (about 90 miles west of Stillwater). Foliage was gone on nearly all of the wheat we saw (also true for southern, southwestern and western OK) but stems were still green to varying degrees. Kernels were mostly at soft to medium dough. Perhaps the most prominent feature was heads turning white or reddish tan (depending on variety). This early senescence/maturity was often spread over entire fields (Fig 1). The cause for this often could be attributed to the high number of tillers produced over the mild winter and then the plants simply ran out of moisture during the hot (often 90s °F and low 100s °F) and windy periods we had in April. Moisture is good now in many of these fields, but the damage has been done. No or only little evidence of root rots and take all could be found in most of these fields. In some fields, we did find evidence of take all and dryland root rot (Fig 2), and possibly some strawbreaker/eyespot, but in most fields the base of culms and roots were cream colored and relatively healthy. Occurrence of this premature whitening is widespread and the start of it was observed the previous week in southern and southwestern OK. However, in most of those fields and the ones we visited this past week there still was a grain crop to be harvested, just not as great as it appeared 3-4 weeks ago. These fields often are mixed in with fields or areas that had sufficient moisture to sustain the high tiller count. Some of the better fields observed were planted later or at a much lower seeding rate (45 lb/acre) that resulted in a thinner stand that handled the periods of drought and heat much better than the really thick fields. Other than this, the Plant Disease & Insect Diagnostic Lab (PDIDL) has continued to receive samples (at least 10 or 12) that have tested positive for wheat streak mosaic virus, High plains virus and/or barley yellow dwarf virus. These samples have come primarily from northwestern and western Oklahoma. However, I’m not sure of the extent and severity of these viruses in northwestern OK, but will probably hear and see more over the next couple of weeks.
|Okla State Agency||
Oklahoma Cooperative Extension Service
|Okla Agency Code||
|Title||Pest e-alerts, 05/04/2012, v.11 no.24|
Oklahoma Cooperative Extension Service.
|Purpose||Wheat Disease Update, Bob Hunger|
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|Digital Format||PDF, Adobe Reader required|
|ODL electronic copy||Downloaded from agency website: http://entoplp.okstate.edu/pddl/2012/PA11-24.pdf|
|Rights and Permissions||This Oklahoma state government publication is provided for educational purposes under U.S. copyright law. Other usage requires permission of copyright holders.|