Pest information courtesy of USFS Fact Sheets:
Fall webworm larvae web over branches then feed
on leaves inside the nest. Nests can be pruned out of small trees or use sprays of Bacillus thuringiensis.
Tent caterpillars also eat foliage in the spring.
Scales of various types attack walnuts. Most
scales can usually be controlled with horticultural oil
The leaves may be eaten by any one of several
caterpillars. These can be controlled with sprays once
Mites cause speckling and yellowing of the leaves.
Brown leaf spot or anthracnose symptoms are
irregular dark brown spots occurring in early summer.
Severely infected trees may be defoliated. Rake up
and destroy infected, fallen leaves.
Canker diseases cause dieback or death of trees.
Infected bark may be discolored, sunken, or have a
different appearance than surrounding healthy bark.
Bacterial blight causes small, irregularly-shaped
spots on the leaves and leaf stems.
Black spots occur
on young nuts and shoots. Nearly ripe nuts have large
black spots on the husks. Infected nuts fall
prematurely or may have husks, shells, and kernels
blackened and ruined.
Powdery mildew causes a white coating on the
During periods of high temperature and drying
winds, walnuts may scorch. Make sure plants have
adequate soil moisture.
More on Tree Insects and Disease