Evaluation of Copper Fungicides and Rates of Metallic Copper for Control of Melanose on Grapefruit in Florida

Several copper fungicides were evaluated over a 3-year period for control of melanose, caused by Diaporthe citri on Duncan grapefruit in Florida. In most cases, two rates of each product were evaluated using a single application per season. The amount of metallic copper applied per hectare explained 37 to 60% of the variability in the melanose severity rating and 34 to 62% of the variability in the percentage of the fruit marketable as fresh from 1992 to 1994. Certain copper products were significantly more effective than others when applied at the same rates of metallic copper. Recommendations will continue to be based primarily on the amount of metallic copper per hectare, but adjustments should be made for the relative efficacy of certain products.