Phytophthora Collar Rot (fungus - Phytophthora cactorum): Black, slimy cankers are formed from the bud union to the lower portion of the trunk. Trees infected with this fungus are stunted and eventually die. It is particularly damaging on the Malling Merton Clones. Most seedlings of Delicious, Melba, McIntosh, and Wheatly are resistant. No chemical control recommended. See section on resistant varieties.

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