Oak, Willow
Symptom Cause  
Irregular tan or brown spots on leaves at veins; expand until leaves die; sometimes sunken spots on leaves
Anthracnose (on plants)
>
Swollen; sunken lesions appear on stems and trunk
Bacterial Canker
>
Lesions develop on twigs; leaves wilt/die
Blight (bacterial)
>
Many holes in branches; limbs girdled sawdust at holes
Borers
>
Holes in leaves
Caterpillars
>
Leaves yellowed between the veins; veins green
Chlorosis
>
Young portions of foliage disappear, or young tips disappear, bark peeled off
Deer
>
Foliage turns pale or mottled
Lacebugs
>
Leaves consumed; tawny egg masses present
Larvae of Gypsy Moth
>
Leaves blistered and curled up
Leaf Blister (fungus)
>
Holes chewed in leaves
Loopers
>
Leaves stippled, yellowing or bronze; dry out and drop may be webbing visible; sometimes galls form on leaves
Mite
>
Leaves turn bronze; wilt; drop
Oak Wilt
>
Leaves covered with white powder
Powdery Mildew
>
Bark of trunk and roots gnawed
Rodent Injury
>
Leaves and branches encrusted with bumps
Scale Insects
>
Mushrooms sprout at base of tree; roots covered with string-like growths
Shoestring Root Rot (fungus)
>
Small twigs drop; or hang with dried leaves
Twig Pruner
>