Entomology and Plant Pathology, Oklahoma State University
127 Noble Research Center, Stillwater, OK74078
Vol. 11, No. 20
Apr 16, 2012
Wheat Disease Update
Bob Hunger, Extension Wheat Pathologist
Friday (13-Apr) I visited the variety trial at Marshall (30 miles west of Stillwater) and at Lahoma (10 miles west of Enid). This was followed by visits to many fields north and northeast of Enid (Kremlin, Billings) and north of Ponca City (Tonkawa, Kildare and Newkirk). Wheat development varied across these locations. The earliest I saw had heads emerging and the latest was through flowering. On average, I would say wheat was in the middle of full bloom.
Leaf rust (LR) pustules were found at nearly all stops, but were at low incidence along the entire route. In Stillwater, I have seen incidences in the 40-65% range, but not in all plots.
Barley yellow dwarf (BYD) spots were present, but as in previous weeks, were not as severe as I have seen it in trials here at Stillwater. No or little dwarfing was associated with the spots, indicating spring infection.
Powdery mildew (PM) was observed at many stops; mostly was on lower leaves. The exception to this was the variety trial at Marshall, where PM was severe (≥65%) on lower leaves and could be found on F-1 leaves.
Stripe rust (YR) at Marshall and Lahoma was severe on the varieties observed to be susceptible this year, including Armour, Garrison, Everest, and Pete. Most of the fields I stopped at along the route were Duster, where only an occasional YR stripe was observed. Be sure to read James Swarts and Erick De Wolf’s commentaries below regarding stripe rust. I concur with their statements regarding race change, but have not observed stripe rust as severe on Jagger and its relatives as on the other varieties.