Effects of Septoria Brown Spot on the Yield Components of Soybeans

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Abstract
In 1978 and 1979, the effects of brown spot caused by Septoria glycines on the yield components of ''Williams'' soybeans at 3 canopy levels were investigated. In 1978, seed weights of plants inoculated with S. glycines were significantly reduced. Seed weight reductions in the upper, middle and lower canopy levels were 8, 11 and 16%, respectively, when compared with uninoculated plants sprayed with benomyl. In 1979, seed weight reductions of 8 and 5% in the lower canopy of naturally infected and inoculated plants were significantly different from seed weights of inoculated plants sprayed with benomyl. Number of pods per plant or of seeds per pod did not differ significantly, except for the greater number of seeds per pod in the upper canopy of inoculated plants sprayed with benomyl in 1978. Brown spot severity, brown spot vertical progress and defoliation were greatest in plots of inoculated soybeans.