How to Diagnose Black Walnut Damage

Black walnut trees, like all other plants, are susceptible to a variety of injuries that reduce or destroy their usefulness. The first step in preventing or controlling these injuries is to identify their cause. Most damage is caused by disease, insects, birds, mammals, or weather.

The link address is: http://www.na.fs.fed.us/spfo/pubs/howtos/ht_walnut/cover.htm