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Bacterial leaf spot |
Small spots, usually pinkish. Lesions may fall out leaving shot hole. Usually does not cause defoliation on ornamental plums. |
No effective controls available. If plants are consistently defoliated try planting a different variety. |
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| Black knot (fungus) |
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Elongated, rough, black swellings on twigs, small branches and sometimes on trunk. |
Prune out and destroy all infected wood in late winter, making pruning cuts at least 6 to 8 inches below infected area. Remove nearby sources of inoculum such as infections on wild cherries and plums. Consider replacing trees with more a more resistant cultivar. (See resistant varieties). Fungicides containing one of the active ingredients, captan, chlorothalonil or thiophanate-methyl may be applied at pre-bloom, petal fall and three more times at 10- to 14-day intervals. Alternatively, make a dormant application of lime sulfur spray. |
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Cherry leaf spot (fungus) |
Small spots, often pinkish. Lesion may fall out, leaving shot hole. Usually does not cause defoliation. |
Does not normally require treatment. |
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Plum pockets (fungus) |
Generally, following cool, rainy weather in spring. Unfolding leaves are curled, swollen, yellow, reddish or purplish and leathery. Also, fruit infections. |
Remove wild plums. Use resistant varieties. Commercial varieties introduced for Europe or Asia are generally not as susceptible. Apply single dormant spray before buds swell in late winter or early spring. Use Bordeaux or other coppers, chlorothalonil, ferbam, lime sulfur or ziram. |
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| University Outreach and Extension does not endorse commercial products. Follow the label on all pesticides. |
