Maple, Sugar
Symptom Cause  
Irregular tan or brown spots on leaves at veins; expand until leaves die; sometimes sunken spots on leaves
Anthracnose (on plants)
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Leaves wrinkled; stunted; leaves fall off
Aphids
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Limbs die; large holes appear; starting at top of tree
Asian Longhorn Beetle
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Many holes in branches; limbs girdled sawdust at holes
Borers
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Twigs, buds, foliage eaten
Box Elder Bugs
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Tissue killed, dark sunken spots in wood; leaves affected, canker on twigs.
Canker (fungus)
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Leaves chewed, tree defoliated; silken threads hanging from the branches
Cankerworms
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White, cottony, cushion-like mass on leaves, stems or branches
Cottony Cushion Scales
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Young portions of foliage disappear, or young tips disappear, bark peeled off
Deer
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Tissue killed, dark sunken spots in wood; leaves affected, canker on twigs.
Dieback (fungus)
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Leaves stippled, yellowing or bronze; dry out and drop may be webbing visible; sometimes galls form on leaves
Gall Mites
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Sooty mold, suck juices from leaves; may kill plant
Mealybugs
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Leaves small, mottled yellow and brown, distorted; defoliates tree
Pear Slug (Sawfly)
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Various color spots on leaves, leaves yellow, dying; leaves drop
Phyllosticta Leaf Spot (fungus)
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Leaves covered with white powder
Powdery Mildew
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Black powdery sooty mold fungus forms on honeydew; branches may die
Sooty Mold
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Tar-like spots on leaves
Tar Spot (fungus)
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Leaves turn yellow at margins, then brown, dry; new leaves stunted; tree dies slowly, branch by branch.
Verticillium Wilt
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