Fungicidal suppression of symptomless latent infections of Monilinia fructicola in European plums

European plums (Prunus domestica 'Stanley') with a high incidence of sympto mless latent infections of Monilinia fructicola, were harvested soft-ripe o r firm-ripe, surface disinfested in NaOCl, soaked for 4 min in fungicide su spensions at 20 degrees C and incubated for 7-11 days at >95% RH at 20 degr ees C. Using soft-ripe fruits, all 12 fungicides reduced brown rot relative to the water check after 7 days incubation, with tebuconazole and flusilaz ole being numerically superior. Using firm-ripe fruits, five sterol-inhibit ing fungicides and iprodione reduced brown rot infections after 7 days incu bation, with tebuconazole, flusilazole and myclobutanil being numerically s uperior. Fruits were soaked for 4 min in suspensions of tebuconazole and fl usilazole at 33, 67,and 100 mg a.i./L, and incubated for 7-8 days. Treatmen ts were moderately effective with no rate response except for soft-ripe plu ms soaked in flusilazole. Five sterol-inhibiting fungicides were applied tw ice at mid-season to Stanley trees having fruits with a high incidence of l atent infection. Only tebuconazole gave temporary suppression of M. fructic ola in excised immature fruits. During postharvest incubation of mature fru its, only those sprayed with tebuconazole, flusilazole, and fenbuconazole, showed a reduction in brown rot, to 45-65% from 89% in the water check. Thi s limited response was attributed to poor adhesion of droplets of fungicide suspensions to the waxy fruit surface at the time of application.