NDSU Crop and Pest Report
Horticulture


ISSUE 7  June 13, 2002

 

TAPHRINA ON PRUNUS

There have been two samples of Prunus sp. (both chokecherry) submitted to the lab this past week that are infected with a fungus called Taphrina, which causes cause diseases affecting leaves, stems, and fruits. Taphrina communis causes a disease called plum pockets only on species of plum (Prunus angustifolia and other wild Prunus spp.) Taphrina deformans causes a disease called peach leaf curl in peaches.

Symptoms of these Taphrina diseases are most obvious on the fruit, but at this time of year, would appear on the leaves. Both the samples submitted to the lab showed leaf distortion with a reddish discoloration. Leaves have a sometimes wrinkled-looking, balloonish swelling part of the leaf. The interior from the back of the leaf will be hollow and green while the swollen portion extruding through the upper leaf surface may be somewhat reddish. On fruit, the symptoms are much more obvious. Fruit becomes distorted and enlarged by as much as ten times the normal size, and the centers will hollow or spongy with or without a pit. Early fruit symptoms are whitish spots or blisters that will rapidly enlarge, later becoming reddish with a velvety gray appearance on the surface. These symptoms are the reason the disease is also called bladder plum or plum pockets.

Taphrina overwinters on twigs and bud scales as conidia. The leaves, shoots, and fruit are infected when cool, wet weather is prevalent in the spring when buds are breaking. The fungus moves very quickly through the developing leaves and fruits, producing the hyperplasia or increase cell growth that gives the swollen appearance of both leaves and fruit. The sexual spore stage of the disease (ascospores) are visible as the velvety gray layer on fruit.

The best management strategy is to use resistant cultivars of Prunus. On susceptible varieties, effective control of Taphrina diseases is a single application of fungicide late in the fall or early in the spring before bud break. Fungicides such as Bordeaux mixture (8-8-100), liquid lime-sulfur, and chlorothalonil are all effective in protecting against Taphrina infection of new growth.

Please check out Dr. Robert Stack’s "Illustrations of Tree Diseases" website for images.

http://www.ndsu.nodak.edu/instruct/stack/TDI/aFOL_DIS_1A.html

Cheryl Biller
NDSU Plant Diagnsotic Lab
diaglab@ndsuext.nodak.edu


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