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Perithecia of Eutypa lata on Sweet Cherry in the Central Valley of California. G. P. Munkvold, Department of Plant Pathology, University of California, Davis 95616. J. J. Marois, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 75:431. Accepted for publication 17 October 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0431A.

Fungal stromata containing mature perithecia and ascospores of Eutypa lata (Pers.:Fr.) Tul. & c. Tul. (syn. E. armeniacae Hansf. & M.V. Carter) were found on sweet cherry trees (Prunus avium L. 'Bing') in a sprinkler-irrigated orchard near Stockton, California. A survey revealed that perithecia occurred on 1.3% of the trees in the orchard. Stromata were found on decorticated cankers below large pruning cuts. Pure cultures derived from the ascospores were used to inoculate healthy limbs of Bing cherry and apricot (P. armeniaca L. 'Blenheim,) and cuttings of grape (Vitis vinifera L. 'Chenin blanc'). After 2 mo, the fungus was successfully reisolated from the xylem canker that developed around the inoculation site of each plant. E. lata causes important dieback diseases of grape and apricot in California and elsewhere. The fungus has a wide host range, but in California it has been reported only from grape, apricot, Ceanothus spp., and chokecherry (P. virginiana L. var. demissa (Nutt.) Torr.). Ascospores are the only known means of disease spread. However, there is only one report of the perithecial stage in California's Central Valley, on a single backyard grapevine. Other reports of the perithecial stage in California have been limited to coastal areas. The presence of perithecia in Central Valley orchards may explain the high incidence of disease (over 50%) in some vineyards in the valley, over 80 km from any previously recognized inoculum sources. This discovery also suggests that sprinkler irrigation of orchards and vineyards in the Central Valley may be sufficient to induce formation of perithecia. This is also the first report of E. lata on sweet cherry in North America