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Effects of Common Root Rot on Winter Wheat Forage Production. C. M. Rush, Associate Professor, The Texas Agricultural Experiment Station, Bushland 79012. J. T. Mathieson, Research Associate, The Texas Agricultural Experiment Station, Bushland 79012. Plant Dis. 74:982-985. Accepted for publication 24 May 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0982.

A 2-yr field study was conducted to evaluate the effects of common root rot, caused by Bipolaris sorokiniana, on winter wheat forage production. Treatments were established that resulted in different levels of disease severity. Disease severity was evaluated on seven cultivars by using three seed treatments including imazalil fungicide, conidial inoculation with B. sorokiniana, and noninoculated, nontreated controls. Forage samples were taken in November and March each year, and plants were evaluated at the same time for disease incidence and severity. At all sampling dates, significant differences (P = 0.05) in disease incidence and severity existed among cultivars and seed treatments. Seed treatment effects were similar on all cultivars as indicated by the lack of any cultivar seed treatment interaction. The imazalil treatment had a significantly lower disease index (DI) than the other two treatments at each sampling date, and the DI of the treatment with B. sorokiniana was significantly higher than the control at three of four dates. Cultivar TAM 200 consistently had a high DI, and the DI of cultivars Scout 66 and Siouxland were consistently low. However, the correlation coefficient between DI and forage production was always low and nonsignificant. Although significant differences in forage production existed among cultivars, they were not related to the disease measured, indicating that control of common root rot is not important when forage production is the primary concern. However, because grain yields may be reduced by common root rot, management practices that reduce disease severity are still highly recommended.