Effects of Copper-Based Fungicides on Foliar Gas Exchange in Tart Cherry

In the Great Lakes, region of the United States, cherry growers are poised to re-adopt copper-based fungicides to manage cherry leaf spot disease (CLS), Caused by Blumeriella jaapii. However, application of copper is often associated with leaf bronzing. In growth chamber experiments, bronzing was observed oil foliage of tart cherry (Prunus cerasus 'Montmorency') seedlings I week following application of it copper-based fungicide, only when leaves were also exposed to nightly dew. In potted, I-year-old trees Outdoors, light-saturated rates of net CO, assimilation (A) and stomatal conductance (g(s)) were not affected by treatment with copper sulfate, chlorothalonil, tebuconazole, or trifloxystrobin compared to a nonsprayed control. In 2005 and 2006. A and g(s) were measured during late summer on leaves of mature trees in in orchard subjected to the following fungicide programs: synthetic fungicides only; synthetic fungicides integrated with copper-based fungicides or not sprayed. Bronzing symptoms were observed on trees sprayed with copper. Regression analysis revealed that neither A nor g(s) decreased its leaf surface area affected by bronzing increased (R-2 = 0.004. P = 0.80 and R-2 = 0.006, P = 0.74, respectively) bronzing associated with application of copper-based fungicides may therefore be inconsequential to foliar gas exchange in tart cherry during title summer.