Factors affecting mummification and sporulation of pome fruit infected by Monilinia fructigena in Dutch orchards

A 2-year field experiment (1997-98, 1998-99) was conducted to study mummification and subsequent sporulation in spring of apple (cvs James Grieve, Golden Delicious) and pear (cv. Conference) fruits infected by Monilinia fructigena . Most mummified fruits were found in James Grieve and Conference, whereas in late-infected Golden Delicious, fruits were still soft when examined in April. In the first year, these late-infected fruits had a significantly higher sporulation intensity per sporulating fruit (P = 0.05) compared with Golden Delicious fruits infected 9 and 5 weeks before harvest maturity, which were partly mummified. It was concluded that early- and late-infected fruits contributed to primary inoculum in the next season. In a postinfection regime of 25degreesC and 65-75% relative humidity under controlled conditions, the number of Conference fruits sporulating decreased rapidly, and after 12 weeks' incubation sporulation had completely ceased. After 8 weeks' incubation, sporulation intensity in the postinfection regime at 10degreesC was significantly higher than that at 20 and 25degreesC in a first experiment with inoculated unripe fruit (P = 0.05). Results of a second experiment with ripe fruit were less clear. These results are discussed in relation to orchard disease management.