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Outbreak of Eremothecium coryli Fruit Rot of Tomato in California

A ripe fruit rot of tomato (Lycopersicon esculentum) associated with stink bug (Euschistus conspersus) feeding caused extensive losses in the Sacramento Valley of California in 1998. Portions of several fields were abandoned at harvest due to fruit rot levels >30%. Symptoms included a soft, water-soaked rot often surrounding a firm, dark green island. Entire fruit sometimes became watery and soft. The ascomycetous yeast, Eremothecium coryli, characterized by spindle-shaped ascospores with long, thin, whip-like terminal appendages (1), was consistently isolated from diseased tissue plated on V8 or potato dextrose agar amended with tetracycline. Ripe tomato fruit were inoculated with a 0.1-ml suspension of 1.5 × 10⁵ ascospores per ml injected to a depth of ≈4 mm to simulate stink bug probing. Fruit were placed in plastic containers and, in initial tests, were held at room temperature. In subsequent tests, inoculated fruit were maintained at constant temperatures of 20, 25, 30, or 35°C. Controls included inoculum either placed on the fruit surface or injected with sterilized water. Each treatment consisted of one to four fruit in two to four replications. All experiments were repeated. Lesions were visible within 5 days after inoculation and were >25 mm in diameter after 7 days. Progression of rot occurred at all temperatures but was fastest at 30 and 35°C. Controls remained symptomless. E. coryli was reisolated from infected fruit. This is the first documentation of field-level losses caused by E. coryli associated with stink bug feeding. Isolates are maintained in the Herman J. Phaff Collection of Yeast and Yeast-like Microorganisms at the University of California, Davis.

Reference: (1) G. S. de Hoog et al. 1998. Eremothecium Borzi emend. Kurtzman. Pages 201-208 in: The Yeasts—A Taxonomic Study. C. P. Kurtzman and J. W. Fell, eds. Elsevier Scientific Publishers, Amsterdam.