Black Leaf Mold Development and Its Effect on Tomato Yield. G. L. Hartman, Plant Pathologist, Asian Vegetable Research and Development Center, P.O. Box 42, Shanhua, Tainan 74199, Taiwan, R.O.C.. T. C. Wang, Associate Specialist, Asian Vegetable Research and Development Center, P.O. Box 42, Shanhua, Tainan 74199, Taiwan, R.O.C. Plant Dis. 76:462-465. Accepted for publication 23 November 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0462.

The severity of black leaf mold, caused by Pseudocercospora fuligena, was compared under epidemic conditions in field experiments on susceptible tomato lines that were either inoculated with the fungus or not inoculated. In one trial, 10 tomato entries that were infected by field inoculum had an average black leaf mold severity of 53 and 60% recorded over two assessments taken during fruit-set. In another experiment, different levels of disease severity were induced on a breeding line, CL 5915-153D₄-3-3-0(CL 5915) and a commercial variety, TN 2, by inoculating plants at various intervals. Both entries had up to 32% less yield than control plants that were kept disease-free with fungicides. CL 5915 had up to 11% and TN 2 up to 28% fewer fruit per plant than disease-free controls. Fruit weight was reduced to 20 and 7% of control plants for CL 5915 and TN 2, respectively. There was a significant negative correlation between the area under the disease progress curve and total yield, fruit number, and weight per fruit.