CONTROL OF ALTERNARIA INFECTION OF FRUIT OF APPLE CULTIVAR NITTANY WITH CALCIUM-CHLORIDE AND FUNGICIDES

Calcium chloride (CaCl2) Was tested for its efficacy in reducing the i ncidence and severity of infection of the apple cultivar Nittany by Al ternaria spp. In 1989, eight biweekly applications of flake (referred to as CaCl2) or liquid CaCl2 reduced the incidence of rot from 61% in the controls to 27 and 33%, respectively. Dip treatments alone reduced rot incidence to 17 and 12% for the CaCl2 and liquid CaCl2 treatments , and seasonal sprays followed by dip treatment reduced incidence to 5 %. Nine CaCl2 sprays, applied biweekly, reduced the incidence of the d isease from approximately 44% in the controls to 12 and 18% in 1990 an d 1991, respectively. Disease severity was reduced from 27 and 14 lesi ons per fruit in the controls to nine and six lesions per fruit in 199 0 and 1991, respectively. In postharvest tests, fruit treated with CaC l2 alone and in combination with iprodione exhibited the lowest incide nce and severity of Alternaria rot after 3 and 6 mo in refrigerated st orage. Best control of Alternaria rot was achieved with nine seasonal applications of CaCl2 followed by a postharvest dip of CaCl2 alone or in combination with iprodione. Fruit were sampled biweekly beginning i n July through harvest to determine the frequency and pathogenicity of Alternaria spp. In 1991, isolation of epiphytic Alternaria spp. was u niform through the growing season, with isolation frequency of 52-72%. Isolation of Alternaria spp. from the same fruit that had been surfac e-disinfested yielded approximately 1-2% in July and increased gradual ly through the remainder of the season. At harvest, isolation frequenc y from surface-disinfested fruit averaged 34%. In 1992, isolation of e piphytic Alternaria spp. increased over the season from 22% in July to 69% at the end of September. Isolation of Alternaria spp. from surfac e-disinfested fruit was 2% in July and 11-16% in September.