Extension impact statement by Assistant Professor Kari A. Peter, Ph.D.

Copper is a common tool in the disease management toolbox for tree fruit growers. As a general biocide, it targets fungi and bacteria; however, it can be phytotoxic to plant tissue and cause damage. Previously, there was a lack of understanding among growers and consultants of how copper worked, as well as an inability to distinguish between bacterial leaf spot on peach and copper injury. This led to overuse of copper and severe damage, as well as yield and financial losses. Dr. Peter developed and led a hands-on workshop providing growers and consultants the opportunity to see a side-by-side comparison of copper injury of different coppers used and bacterial spot disease on different peach tree cultivars. Specific activities were designed to train participants to distinguish differences in shape and location of lesion, color of leaf, etc., and quizzes were administered to ensure that all participants could correctly assess samples. The workshop was summarized for greater outreach in an article for Fruit Times and American Fruit Grower. The topic was further developed for presentations for the 2016 winter educational tree fruit grower meetings where, additionally, factors that influence copper phytotoxicity, pH in particular, were presented. Of the fifteen field workshop participants, six were consultants and, when taking into consideration the clients they serve, at least 150 growers would be impacted by having someone on their team able to know if bacterial spot is an issue, or if copper is causing injury if it were used. The tally from all evaluations from the 2016 winter tree fruit grower meetings (nine meetings in total for Pennsylvania) indicated that an average of 95.6 percent of the respondents gained a moderate to a considerable amount of knowledge after hearing the presentation about understanding how copper worked and its use for disease management; 73.4 percent of the respondents said what they learned would improve the efficacy of their copper applications. Consequently, copper applications will be more effective, less copper will be put into the environment, and ultimately the growers' bottom line will increase by $15,000-$20,000 per year.

Contact Information

Kari A. Peter, Ph.D.
  • Associate Research Professor, Tree Fruit Pathology