Effect of Temperature, Wetness Duration, and Inoculum Density on Infection and Lesion Development ofColletotrichum coccodeson Tomato Fruit

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Abstract
The influence of temperature on lesion development and sporulation of Colletotrichum coccodes was determined on detached tomato fruit. Lesions did not develop after 8 days of incubation on spray- or puncture-inoculated fruit incubated at 7 C. Lesion diameter of spray- or puncture-inoculated fruit was greatest at 25 or 31 C. Spray-inoculated tomatoes incubated at 25 or 31 C developed more lesions than those incubated at 16 C. The number of conidia produced per lesion increased with increasing temperature from 16 to 28 C and decreased at 31 C. Lesions did not develop on tomato fruit that received 0, 3, or 5 hr of continuous wetness. Disease incidence was 35, 75, 92, 100, 100, 100, and 100% on tomato fruit that received 10, 20, 24, 29, 44, 48, and 53 hr of continuous wetness, respectively. Disease severity increased with increasing hours of wetness duration and peaked at 48 hr. Disease severity increased with increasing inoculum density from 101 to 106 conidia/ml, and was greatest at 106 conidia/ml. Germination of conidia obtained from 7-day-old lesions on tomato fruit incubated in near 100% relative humidity (25 C) was 73.4%. Germination was 35.7, 36.3, or 24.6%, respectively, after lesions on tomato fruit were exposed to 2, 8, or 24 hr of drying at room temperature (27-30 C) and 55-75% relative humidity.