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Disease Detection and Losses

Yield Loss of Maize Caused by Kabatiella zeae. Francisco J. B. Reifschneider, Centro Nacional de Pesquisa de Hortaliças, EMBRAPA, C.P. 11.1316, 70.000 Brasilia, D. F., Brazil; Deane C. Arny, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 73:607-609. Accepted for publication 10 November 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/Phyto-73-607.

The effect of eyespot disease, caused by Kabatiella zeae, on yield of maize (Zea mays) and the relationship between yield and disease rating at different plant growth stages and inoculation frequencies were studied using inbred W64A (susceptible to K. zeae) in 1978 and inbreds W64A and Oh43 (resistant) and hybrids W64A x Oh43 and W64A x A632 in 1979 on a plowed field (PL) and on a field kept under minimum tillage, with debris on the surface (DB). In 1978, inoculations significantly decreased grain yields. Weekly inoculations reduced grain yields 44 and 33%, respectively, on PL and DB. Yields of uninoculated plants, however, were 20% lower on DB than on PL. In 1978 and again in 1979, reductions due to biweekly and monthly inoculations were similar. In 1979, average yield reduction for all inbreds and hybrids on both PL and DB, due to the natural occurrence of eyespot, was 9% lower than for fungicide-sprayed plants. Differences due to treatments and inbreds and hybrids on both PL and DB were highly significant, and the interaction of treatment by inbred or hybrid was highly significant on DB. Regressions of grain yields on disease ratings at late whorl, silk, or soft dough stages were highly significant for all inbreds and hybrids on both PL and DB. Silk was considered the best plant growth stage for eyespot evaluation, because ratings covered the range of the disease rating scale used. The destructive potential of K. zeae was considered similar to that of Helminthosporium carbonum.