Post-infectional Activities of Non-systemic Fungicides Against Apple White Rot

In order to develop an effective spray program for control of apple white rot with reduced use of fungicides, the control efficacy of several fungicides that has been intensively used for control of the disease was assessed. They were sprayed on the same tree with 15 day interval from late May to early August. Just prior to and after each spray, 100 fruits were bagged with two layered fruit bag to limit the chemical application in only one time, and the disease incidence and latent infection frequency on the bagged apples were examined. Some fungicides such as folpet, iminoctadine-triacetate and azoxystrobin showed a high post-infectional activity even though the former two are non- systemic. Folpet suppressed symptom development, iminoctadine-triacetate reduced infection frequency and azoxystrobin acted in both ways. When those fungicides were ！！ adopted in a spray program, once in a cropping season, their post-infectional activity became much greater. This activity shown by the non-systemic fungicides was supposed to be derived from the peculiar infection process of the white rot fungus of which the pathogen is usually remain latent in the corked cells of lenticel until the apple reach mature stage.