Thesis (Ph. D.)--University of Wisconsin--Madison, 1945. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 84-90).

Antagonistic effects of Epicoccum purpurascens, Aureobasidium pullulans, Trichoderma spp., and Botrytis cinerea on establishment of Monilinia fructicola infections in cherry and peach blossoms were assessed in field and mist chamber studies. Conidia of each fungus were applied to blossoms that were subsequently inoculated with conidia of M fructicola. Mist chamber experiments on forced cherry blossoms demonstrated that recovery of M. fructicola was significantly reduced (P=.05) when spores of E. purpurascens and B.cinerea had been applied 24 hr prior to inoculation with M. fructicola. Reduction in recovery of M. fructicola was comparable to that obtained with the fungicide benomyl. In field trials done in 1990 and 1991, applications of E. purpurascens and A. pullulans reduced cherry blossom blight relative to nontreated blossoms by 47 to 65 and 54 to 58%, respectively, compared to reductions of 80 to 96 and 84 to 97% with the fungicides benomyl and iprodione, respectively. Twig blight in peach, an indicator of blossom blight infection, was reduced by 37% relative to nontreated blossoms with applications of E. purpurascens, compared to 54 and 51% reductions with benomyl and iprodione, respectively. Analysis of the influence of antagonistic fungi sprayed onto blossoms on fruit set indicated that B.cinerea was a weak pathogen of stone fruit blossoms. Significant reductions (P=.05 and P=.10) were obtained in fruit set compared with the nontreated control when conidia of B. cinerea were applied to both cherry and peach blossoms in 1991. Latent Monilinia infections were evaluated by dipping green cherries in the herbicide paraquat. Applications of E. purpurascens and A. pullulans to blossoms caused reductions in the number of latent Monilinia infections in green cherries by 18 and 49%, respectively in 1990, and 61 and 66% respectively in 1991. This compares with reductions of 98 and 92% in 1990 and 1991, respectively, with the fungicide iprodione. It was observed that the antagonists E. purpurascens and B. cinerea also became established as latent infections. These fungi were recovered at a significantly (P=.05) higher percentage on green cherries where they had been applied as antagonists to blossoms. No meaningful differences were detected in the amount of brown rot that developed on fruit due to the influence of fungal treatments on blossoms. / Graduation date: 1992

M. Tech. Agriculture / Brown rot caused by Monilinia laxa is the main pre and postharvest disease of peaches; it affects the shelf life and marketability of peaches. Increasing consumer concern regarding food safety makes it necessary to search for natural environmentally friendly alternative products for postharvest disease control. The objective of this study is to develop an environmentally friendly essential oil technology for the control of brown rot (M. laxa) in peaches at postharvest stage to replace the currently used synthetic fungicide (Iprodione)