Effect of conidial concentration of Monilinia fructicola on brown rot development in detached cherries

Mature sweet and sour (tart) cherries, free of fungicide residues, were harvested, arranged in trays and inoculated without wounding with single 33 mu L drops containing 1 x 10(3) to 1 x 10(6) conidia/mL of Monilinia fructicola. After 22 h wetting at 20 degrees C, fruits were dried (2-4 h), incubated at 20 degrees C, and evaluated daily for development of lesions and sporodochia for 8 da or 9 da post-inoculation. For sweet cherry fruits, increasing the inoculum concentration advanced initial lesion appearance from 5 da to 2 da post-inoculation, increased the incidences of fruits with lesions from 23% to 99% (9 da) and increased the proportions of fruits with sporodochia from 21% to 99% (9 da). The response pattern of ripe sour cherry fruits was very similar, with initial lesion appearance advanced from 4 da to 2 da, and the incidences of fruits with lesions and sporodochia increased from 9% to 92%, and from 9% to 91%, respectively, after 8 da postinoculation incubation. Fruits of Vista sweet cherry were five times more susceptible to infection than those of Montmorency sour cherry. Longer wetting durations of 36 h and 48 h, increased lesion and sporodochial development of Bing sweet cherry fruits, especially from low inoculum concentrations. Similar numbers of conidia applied in 3-10 mu L drops induced a slightly higher incidence of lesions than when applied in 30 mu L drops. The responses of the proportions of fruits with lesions or sporodochia to inoculum concentration and post-inoculation incubation time, or inoculation wetting duration, were described by polynomial models.