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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

The present study was undertaken to examine the litter decay fungi of red cedar (Thuja piicata Donn). The fungi involved in conifer litter decay have not been examined intensively and there has been no study of red cedar litter decay. Since Thuja is often found in wet, poorly drained areas, it provided an opportunity to observe occurrence of litter decay fungi relative to slight differences in distance from a stream margin. This was determined by observing changes in the frequency of the fungi at various distances from the margin of a stream and also by observing seasonal changes in fungal populations. An ordination of the data was performed to determine if there were species associations which would characterize the relatively minor horizontal and vertical spatial changes in the sites. The sites were divided into subsites (high, middle and low with respect to the stream) and samples were taken at each subsite. Red cedar branchlets from the L and F litter layers were washed and plated on a selective medium or placed in moist chambers; all observed species were isolated and identified. Most of these were members of the Fungi Imperfecti. The frequency of occurrence of the more commonly isolated species was utilized in a Principal Components Analysis (PCA) to determine associations of subsites, layers or species. There was little distinction between the three subsites, but there was a general separation of the high subsite from the low subsite, the middle subsite showing affinities to both. The L and F layers represented a division of the litter layer which formed more distinct clusters in the ordination, especially in the Site B data. Seasonal distinction among the samples seemed to reflect the extremes of the seasons. The spring and summer samples generally grouped together, as did the fall and winter samples. Species associations reflected various combinations of the above groupings, depending on the species groups involved. Again the most distinct groups represented extremes, e.g., species prominent in dry samples, especially in the high subsite, or species prominent in moist conditions, especially in the low subsite. No single variable provided clear distinction among the various subsites, layers, seasons or species. However, the combination of all of these gave general indications as to probable fungal associations. / Science, Faculty of / Botany, Department of / Graduate