The bark at the base of an infected branch is loose and peels off readily from the gray to black discolored wood beneath. The annual removal and destruction of all leaves that have lodged in crotches is recommended. Applications of a copper fungicide or lime sulfur have been shown to be very effective in preventing canker. The first application should be made after the dead leaves and dying branches have been removed and before growth starts in the spring. Read and follow all directions on the label.
Symptoms consist of leaf bronzing, stunted growth and general decline of boxwood.
The microscopic worms feed on the roots, which soon die and the plant forms lateral roots above the invaded area. These lateral roots in turn are infested. Repeated infestations and lateral root production result in a stunted root system resembling a witches broom. Nematodes cannot be totally eliminated from the landscape. The goal is to keep the population low enough to prevent damaging symptoms that weaken the plant.