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Yield Reduction in Almond Related to Incidence of Shot-Hole Disease. L. M. Highberg, Research Assistant, Department of Plant Pathology, University of California, Davis 95616. J. M. Ogawa, Professor, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 70:825-828. Accepted for publication 17 March 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-825.

The effect of shot-hole disease, caused by Stigmina carpophila, on yield of Nonpareil almond was studied in two commercial almond orchards. Differences in disease severity among plots were obtained when various fungicides were applied over several years. Higher yields were obtained from treatments that significantly reduced disease severity. In a Merced County field plot where various fungicide treatments had been applied, disease severity in 1982 was 89 and 90% lower and yields were 283 and 240% higher, respectively, for the ziram and captan petal-fall spray treatments than for the untreated control. Similarly, in a Kern County field plot, a 2-yr treatment consisting of three bloom-time ziram spray applications resulted in 59% lower disease severity in 1982 and 36% higher yield than for the untreated control. Differences in kernel size and weight between treatments were not observed. Higher yields can be maintained with fungicide applications that significantly reduce disease incidence.

Keyword(s): Coryneum beyerinckii.