The standard schedule for the control of walnut blight in California—one prebloom and one or two postbloom treatments with copper—depends on very accurate timing. If errors are made, control of the disease may not be achieved. Because of climatic conditions, sprays are sometimes applied when blooming is at an end. This is too late because the causal organism has had a chance to infect susceptible parts of the plant.

The above progress report is based on Research Project No. 1124.