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Development of Apothecia from Stone Fruit Infected and Stromatized by Monilinia fructicola in California

Apothecia were produced in the orchard, lath house, and laboratory from peach and nectarine fruit infected and stromatized by Monilinia fructicola. Fully stromatized “mummies” and nonstromatized infected fruit were placed in the orchard either on the soil surface or buried to a depth of 2 to 3 cm. Mummies were placed in the orchard at monthly intervals from August to February in 1993-94 and 1994-95. Nonstromatized infected fruit, which were fleshy and decomposed rapidly, were soon unavailable and were only placed in the orchard in August and September. Apothecia developed in February and early March only from mummies that were placed in the orchard in either October, November, or December. Mummies placed in the field in August, September, January, and February did not produce apothecia. Leaving mummies on the soil surface versus burying them 2 to 3 cm did not affect the development of apothecia. Apothecia were never produced from nonstromatized or recently-infected (fleshy) fruit. In the laboratory, apothecia were only produced from mummies that were partially buried in moist sand and stored without light at 2°C and >97% relative humidity (RH) for more than 8 weeks prior to incubation for 2 weeks (12, 15, or 20°C) with a 12-h photoperiod. Mummies that were incubated at >97% RH for less than 8 weeks or incubated at <90% RH never produced apothe-cia when stored at 2°C and then transferred to warmer temperatures with light. In orchard experiments, apothecia were only observed in plots with nondisturbed orchard floor vegetation; whereas no apothecia were found in either herbicide-treated or rototilled plots. Apothecia in the San Joaquin Valley were only produced from mummies that were subject to an 8-week or greater cold-temperature incubation while in contact with soil.