![]() ![]() Leaves on the infected twigs turn brown and collapse but remain attached to the tree. Symptoms: Brown rot ( Monilinia fructicola) symptoms first occur as the browning of blossoms and the death of twigs. Photo Credit: Mary Ann Hansen / Wikimedia Commons / CC BY 3.0Ĭherry Trees Affected: The Kwanzan flowering cherry tree is one of the most susceptible cultivars, but many stone fruits, including peach and plum trees, are affected. ![]() Risk: Black knot can limit the production of cherries and ruin the appeal of ornamental cherry trees. Season: Infection occurs from April through June. The Wisconsin Horticulture Division of Extension does not recommend using fungicides since treatment is expensive and likely to be ineffective. Remove cherry trees that have a severe infection. Burn or bury all infected material otherwise, it may still be able to infect healthy trees. Treatment: Prune 3-4 inches below the knot during the dormant season. As the year progresses into summer and fall, the knots become hard, rough, and black. The following spring, the growing knots develop the olive-green fungal growth. By fall, light brown swellings appear on infected twigs. The spores can germinate and infect new plants in six hours at the optimal temperature and wet conditions. ![]() The rain and wind then carry the black knot fungus spores to susceptible plants. Infected branches may wilt, not grow leaves, and can eventually kill the entire tree.Ĭauses: Through spring and summer, mature knots produce spores. ![]() Diseased twigs often bend due to knot overgrowth. Velvety, olive-green fungal growth may cover the knots. These knots appear in various areas around the tree and enlarge when the disease is left untreated. Symptoms: Black knot ( Dibotryon morbosum) appears as hard, black swellings or knots, which may stretch 1-6 inches on the tree. Black knot-resistant cherry tree varieties include East Asian cherry, North Japanese hill cherry, and Prunus maackii (Manchurian cherry or Amur chokecherry). Photo Credit: Scot Nelson / Flickr / CC0 1.0Ĭherry Trees Affected: Common among most Prunus varieties, including ornamental, edible, and native types. ![]()
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