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

Abstract

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 25°C 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 10°C was significantly higher than that at 20 and 25°C 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.