Brown Rot of Dried Plum in California: New Insights on an Old Disease

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Brown Rot of Dried Plum in California: New Insights on an Old Disease

Themis J. Michailides
Yong Luo
Zhonghua Ma
David P. Morgan
Department of Plant Pathology, University of California Davis,
Kearney Agricultural Center, Parlier, CA 93648

Corresponding authors: T. J. Michailides (themis@uckac.edu) and Y. Luo (yluo@uckac.edu)
Michailides, T., Luo, Y., Ma, Z., and Morgan, D.P. 2007. Brown Rot of Dried Plum in California: New Insights on an Old Disease. Online. APSnet Features. doi: 10.1094/APSnetFeature-2007-0307

Causal Pathogens
Brown rot is an economically and ecologically important disease of dried plum caused by two ascomycete fungi, Monilinia fructicola (G. Wint.) Honey and M. laxa Aderhold & Ruhland (8). These pathogens can cause blossom blight in spring, rot of green fruit in mid season, and decay of mature fruit in late season (3,8,22,46). M. laxa usually causes more severe blossom and twig blights, while M. fructicola causes more severe fruit decay. In addition, M. laxa is common on almonds and apricots, while M. fructicola is currently the dominant pathogen causing brown rot of peaches, nectarines, and plums. Major changes in the populations of Monilinia spp. in dried plum orchards have occurred over the years. In the past, M. laxa was the most common brown rot fungus found in dried plum orchards in California. Now the pathogen population has shifted and M. fructicola is the more prevalent species (39). A partial explanation of the shift of the two species in dried plum orchards is the fact that M. laxa isolates have been sensitive to benzimidazoles fungicides while those of M. fructicola developed resistance to these fungicides and predominated in orchards.

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