Calyx and stem mold, affecting pear fruit cosmetic quality: diagnostic, etiology and management strategies

SOSA MARIA CRISTINA; LUTZ MARIA CECILIA; CONDOPLO NADIA CAROLINA; VERA LUCAS; FAGOTTI PAMELA

Simposio; III International Symposium on Postharvest Pathology; 2015

Argentina is the largest producer and exporter in the Southern Hemisphere of short, medium and long shelf life pears. During 2014?s storage and retail, European markets claimed the presence of a white-grayish mold in calyx and stem affecting fruit?s cosmetic quality. In Packham`s Triumph and Beurre D´Anjou fruits, observation by light microscopy was performed, typical structures of Alternaria spp and Cladosporium were identified. Koch´s postulates were carried out. Fruits, with mold, which were incubated in moist chamber (22°C-7days) did not developed decay; however, in pathogenicity tests in pear fruits all isolates of Alternaria spp. were pathogenic. The hypothesis is that calyx and stem mold by Alternaria spp. and Cladosporium spp. originates in the orchard from spores that infect, and remain dormant until the tissues become senescent during storage. Hence, monitoring of the fungal micro flora of stem, sepals and fruit bottom (calyx) was performed. Both pathogens were from setting fruit, with prevalence in sepals of Cladosporium spp. (20%) at 15 days after full bloom (DAFB) and Alternaria spp. (76%) at 60 DAFB. In the search for putative management strategies, effectiveness of pyraclostrobin and boscalid (Bellis, Basf) was evaluated. This fungicide inhibited the mycelial development of Alternaria spp. (98%), and of Cladosporium spp (100%). In 2014-2015, to assess the effectiveness of these fungicides in controlling mold of pear fruit, they were applied in the orchard 7 days before harvest. Furthermore, the effect of disinfectants over cross contamination in pool immersion (line of packing) was evaluated. Peracetic acid was the best disinfectant since reduced the incidence of mold in about 33%, even 30ds at -1/0°C plus 7ds at 22°C. The calyx and stem mold of pear fruit by Alternaria and Cladosporium can be controlled using combined strategies pre and post-harvest that improves the cosmetic quality of the fruit.