First Report of Tan Spot Caused by Drechslera tritici-repentis on Winter Wheat in Arkansas. M. C. Hirrell, Southeast Research and Extension Center, Monticello, AR 71655. J. P. Spradley, J. K. Mitchell, and E. W. Wilson. Cooperative Extension Service, Little Rock, AR 72203; Department of Plant Pathology, University of Arkansas, Fayetteville 72701; and Cooperative Extension Service, Morrilton, AR 72110. Plant Dis. 74:252. Accepted for publication 21 November 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0252D.
Drechslera tritici-repentis (Died.) Shoem., causal agent of tan spot of wheat (Triticum aestivum L.), was isolated from diseased soft red winter wheat plants (cv. Florida 302) in Conway County, Arkansas, in March 1989. Diagno i was confirmed by the production of conidia 45- 200 µm long with conical basal cell on agar media and by completion of Koch's postulate. The 81-ha field had a history of reduced tillage and summer fallow since 1986. At soft dough (Feekes' growth stage 11.1-11.2), disease incidence (based on plants) was greater than 95% and disease severity of flag leaves ranged from 1 to 10% of leaf area affected. The yield was 1,210 kg/ha, a decrease of approximately 65% for typical yiclds of Florida 302 in 1989. Wheat traw from the prcviou year was examined for the teleomorph (Pyrenophora tritici-repentis (Died.) Drechs.), and pseudothecia were observed to be empty. This is the first report of this disease in the Mississippi Delta area.