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Studies detailed in this paper are not original research but a summary of the literature with microscopic and cultural studies intended to familiarize the writer with some of the more important fruit diseases. Material where available was brought into the laboratory and microscopic studies made of the host symptoms and causal organisms. Hesler and Whetzel's “Manual of Fruit Diseases," “The Plant Disease Reporter,” and “The Experiment Station Record" were found to be of much value in descriptive and reference work and "The Plant Disease Reporter” was considered authentic for nomenclature of the organisms. The pen and ink drawings accompanying each disease are diagrammatic representations and comparative magnifications are not given. / M.S.

The status of Curvularia lunata as a primary pathogen of creeping bentgrass (Agrostis palustris) has been debated in the literature for many years. The most recent and most complete evidence indicates that this fungus is a weak pathogen, colonizing only senescing tissues. In the present study, four groups of experiments were conducted: 1) The effects of five herbicides on the growth of C. lunata in vitro were determined. 2) Acute high temperature stress was evaluated as a predisposing factor in the susceptibility of creeping bentgrass to C. lunata. 3) The effects of acute high temperature stress and exposure to five different herbicides on creeping bentgrass were evaluated together and separately. 4) The potential of chronic, moderately high temperature stress and exposure to five herbicides when occurring separately and together to serve as predisposing factors on the susceptibility of creeping bentgrass to C. lunata were evaluated. It was found that effects of the herbicides on the growth of C. lunata depend on both the specific herbicide and the concentration. High temperature stress and herbicide exposure increase the colonization of creeping bentgrass by C. lunata only to the extent that these treatments produce moribund plant tissue. / Master of Science

A disease of boxwood, so called "boxwood blight", began causing serious damage to boxwood plants after·the drouth of 1930. Four fungi were isolated from the affected parts of diseased plants. Macrophoma candollei waa isolated from the leaves, a species of Fusar1a from diseased stems and twigs, a species of Coniothyrium from the cankers on the stems, and a species of Verticillium from the infected roots. Inoculation experiments were performed on healthy young boxwood plants that were growing in the greenhouse. Pure cultures of Fusaria, Coniothyrim, and Verticillium were used as inoculum. In general the results were negative. The Fusarium culture was the only one that produced any infection and that infect1on waa very slight. Observations made of infected plants in the greenhouse at V.P.I. and at a nursery at Marion, Virginia, and. also a nursery at South Boston, Virginia, indicate that probably the fungi associated with boxwood blight, infect only thoae plants that have been weakened by some physiological condition such as lack of moisture, winter injury, malnutrition, insect injury, or improper transplanting. / M.S.

These experiments have proved conclusively the effect of cedar rust on the normal processes of the apple leaf. The diseased leaves use more oxygen and give off more carbon dioxide than the healthy leaves, and at the same time less starch and sugar is made than in the healthy leaves. When transpiration is reduced, the food supply - the soluble plant food - is accordingly reduced. The difficulty of diseased trees not being able to get sufficient food through insufficient transportation, by water, may be overcome by either of two methods - (1) irrigation or (2) fertilization, with neutral or slightly acid fertilizers, manure being an excellent material to use. The first and most important method of cedar rust control is to cut the cedars for a distance of at least a half mile from the orchard. Second in importance is by timely sprayings, and third, is by feeding the trees. In order that cedar rust control is to be realized, cooperation in a community is essential. “Team work" is necessary in all lines of work and the orchardist should not forget this fact. / Master of Science

Master of Science