Importance of Secondary Inoculum in Strawbreaker Foot Rot of Winter Wheat. G. W. Bruehl, Professor, Department of Plant Pathology, Washington State University, Pullman 99164. R. Machtmes, Technical Aide, and T. Murray, Research Assistant, Department of Plant Pathology, Washington State University, Pullman 99164. Plant Dis. 66:845-847. Accepted for publication 17 December 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-845.

Inoculations with conidia of Pseudocercosporella herpotrichoides in November (1979) reduced yields of a susceptible wheat (Sel. 101) by 56%. Inoculations in February and March (1980) had little effect on yield or bushel weight, but severe lesions developed on many stems. The early infections, representing the effect of primary inoculum, contributed most to yield loss, but the late infections, representing the effect of secondary inoculum, added to the amount of inoculum for succeeding crops. Inoculations of the same wheat three times, once each in November, December, and February, did not increase disease appreciably over that resulting from a single heavy inoculation in November. A single, heavy fall inoculation is recommended for variety screening trials.

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