Shade trees are being killed in large numbers by one or more disease- causing pathogens. The most important disease of oak trees is oak wilt. I have been involved with other scientists to develop a control for this vascular wilt pathogen. Working as a team, field trials have been conducted on trees to evaluate the use of chemicals to control this fungus. In addition, I have conducted field trials to develop control programs for oak leaf blister, ball moss infestations and the parasitic plant, mistletoe.
Vegetables are susceptible to several foliage, fruit, and root pathogens.
One of the goals of my program is to identify vegetable varieties that are resistant to one or more major pathogens. A second goal is to identify fungicide programs that can be used in conjunction with resistant varieties to insure maximum production of high quality vegetables. The principle diseases that have been studied are downy mildew of cucurbits, black rot of crucifers, virus diseases of cucurbits, bacterial leaf spot of peppers, white rust and downy mildew of mustard, and virus diseases of mustard and turnips. As extension program leader, I have the overall responsibility for the extension plant pathology program. Selected Publications Johnson, J.D., R.S. Halliwell, and J. Trampota.