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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.

Phytophthora parasitica is an important root rot pathogen of American and English boxwood, Buxus sempervirens and B. sempervirens var. suffruticosa, respectively, shrubs used extensively in the landscape in Virginia and North Carolina. Studies were undertaken to screen microorganisms for antagonism to Phytophthora in vitro; test two polymers, carboxymethyl cellulose (CMC) and methylcellulose (MC) for their suitability as carriers, storage media, and carbon substrates; and finally to determine the efficacy of selected antagonist pairs in controlling Phytophthora root rot on containerized American boxwood. On the basis of in vitro inhibition tests, 14 organisms were selected. These included six bacteria, five fungi and three actinomycetes. Populations of conidia-forming fungal isolates increased or remained fairly stable when stored in 0.25% suspensions of CMC and MC, indicating that spores may be a more suitable propagule than mycelial fragments when storing fungal isolates for more than 1 week. No significant or consistent changes in population viability occurred among the actinomycete and bacterial isolates. Carboxymethyl cellulose was a more readily utilizable carbon source than MC as indicated by the smaller specific growth rates of microorganisms in MC. Methylcellulose was not utilized by actinomycete and non-spore-forming fungal isolates. Six of seven antagonist pairs were efficacious in controlling root rot in the greenhouse when suspended in CMC. In general, application of antagonist pairs to boxwoods stimulated growth relative to control plants. The polymers may provide the biocontrol organisms with a protective environment and/or food base for establishment of stable population levels in the infection court, providing protection of the root system when challenged with the pathogen. / M.S.