ENHANCED RESISTANCE TO SIDE ROT IN PEARS TREATED WITH CALCIUM-CHLORIDE DURING THE GROWING-SEASON

Incidence and severity of side rot in Bosc pears were reduced in fruit from trees treated with CaCl2 sprays during the growing season. Trees were treated every 2 wk beginning in early July for a total of three applications of CaCl2 at 0, 1.2, 3.6, or 6.0 g/L of calcium. Mature fruit were wound-inoculated postharvest with spore suspensions of Phialophora malorum at 0, 10, 10(2), 10(3), or 10(5) spores per milliliter. Lesion diameter was measured after 3 mo of storage at 0 C. A significant interaction between rate of CaCl2 and spore concentration was observed. At 6.0 g/L of calcium, the mean area of decay was reduced at spore concentrations > 10(2) per milliliter. At 3.6 g/L of calcium, lesion area reduction was significant at 10(2) and 10(5) spores per milliliter. At 1.2 g/L of calcium, lesion area reduction was significant only at 10(2) spores per milliliter. CaCl2 treatment reduced incidence of side rot in naturally infected fruit in 3 yr of trial. CaCl2 did not reduce incidence of decay of pear by Penicillium expansum. Calcium concentration in mature fruit peels was related to level of CaCl2 treatment.