Use of Soil- and Foliar-Applied Calcium Chloride to Reduce Pear Susceptibility to Brown Spot (Stemphylium vesicarium)

We evaluated the effectiveness of soil and foliar applications of calcium chloride (CaCl2) on reducing pear susceptibility of brown spot (Stemphylium vesicarium). Two experiments were done using pear trees of the variety Abbé Fetel grafted on quince (Cydonia oblonga) rootstock. Potted trees were treated with soil and foliar application of CaCl2, while commercial trees were subjected only to soil application of 5.6 g CaCl2 L−1, and 11.2 g CaCl2 L−1. In a controlled environment, leaf and fruit brown spot incidence decreased with the increase of residual calcium (Ca) concentration in the tissue, according to a second degree function. In fruits from field experiment, disease symptoms were decreased by soil application of CaCl2 that increased Ca fruit concentration above 1000 mg kg−1 dw; however, no clear correlation between fruit Ca and brown spot incidence was found. Leaf water and osmotic potential were not related to brown spot incidence.