Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2013
Publication Date: 6/30/2013
Citation: Xiao, C., Boal, R.J. 2013. Sources and availability of Sphaeropsis pyriputrescens inoculum in apple orchards. Phytopathology. 103:S2.163. Interpretive Summary:
Technical Abstract: Sphaeropsis pyriputrescens (SP) is the cause of Sphaeropsis rot, a recently reported postharvest fruit rot disease of apple. Infections of apple fruit by the fungus occur in the orchard, and symptoms develop during storage or in the market. SP also is the cause of a twig dieback and canker disease of apple and crabapple trees. To determine sources of SP inoculum in the orchard, twigs with dieback and canker symptoms, dead fruit spurs and bark, and fruit mummies on the trees were collected and examined for the presence of SP pycnidia. To monitor inoculum availability, 3 twigs with dieback from each of 10 crabapple trees and 3 dead fruit spurs or twigs from each of 10 trees in a Fuji orchard as well as 5 pieces of dead fruit spurs and 10 pieces of dead bark tissues from each of 10 trees in a Red Delicious orchard were sampled periodically during the fruit-growing season. Samples were exampled for the presence of SP pycnidia and viability of pycnidia was assessed. SP pycnidia were observed on diseased twigs, dead fruit spurs and bark, and mummified fruit on both apple and crabapple trees, suggesting that these tissues were the sources of SP inoculum in the field for fruit infection. During the three growing seasons, viable SP pycnidia were observed in 50-100% of the Fuji trees, >90% crabapple trees, and 10-50% of the Red Delicious trees, indicating that viable inoculum for potential fruit infection was available at any sampling time during the fruit-growing season.