- Shade trees such as maple are often infected with tar spot and leaf spot. Tar spot affects many different species, while leaf spot mainly damages Japanese, red and silver maples, and Amur trees. Anthracnose infects a range of trees including hickory, walnut and elm. Ornamental plants are also susceptible to diseases such as powdery mildew and botrytis blight.
- Maples infected with tar spot develop large yellow spots that later blacken. Leaf spot is characterized by tan spots that have reddish-purple borders. Anthracnose infections create spots around the leaf veins, shoots and buds, causing wilting and death. Powdery mildew appears as a spotted grayish-white dusting over leaf surfaces. Botrytis also begins as a grayish-white powder but soon darkens to gray.
- Tar spot and leaf spot cause minimal damage, and fungicide is rarely necessary. Anthracnose is more serious on younger trees; the damage is mainly aesthetic on established trees. The type of fungicide varies depending upon the tree. Treat powdery mildew and botrytis blight with fungicides appropriate to the plant. Prevent the spread of these diseases by gathering up and destroying fallen leaves that may be contaminated with fungal spores.
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