Paul D. Manion

Evaluation of Possible Effects of Acid Rain on Scleroderris Canker of Red Pine in New York

The possible affects of acid rain on Scleroderris canker of red pine were evaluated through two procedures. In the first, red pine seedling field plots, protected and unprotected from natural rain, were exposed to natural inoculum and treated with either deionized distilled water (pH 5.6), artificial acid rain (pH 3.5), or lime. Acid rain treatments did not increase disease infection levels over distilled water or lime treatments. Soil pH was slightly lowered by acid rain treatments. The second procedure evaluated pH and buffering capacity of red pine bark and buds from twelve plantations in the Adirondack region of New York. In addition, soil pH and soil cation content of the stands were determined and evaluated in relation to bark pH and natural Scleroderris canker disease increase rates. The effect of acid rain on red pine bark is probably minimal since bark surfaces were generally more acidic than acid rain. Buffering capacity against acid was small. Soil pH and spring bark surface pH were found to be inversely correlated with disease increase. These two procedures generated contrasting interpretations: (1) Scleroderris canker disease did not increase in response to artificial acid rain treatment of seedlings; (2) Scleroderris canker disease increase rate in red pine stands was somewhat related to soil pH. None of these relationships are very strong, and, therefore, it would appear that the various interacting factors of acid rain on the system generate a neutral minor impact on the Scleroderris disease problem in New York.

Hypoxylon canker incidence and mortality in naturally occurring aspen clones

Cankers low on the bole were associated with mortality. Small stems had more cankers below the lowest living branch. The frequency of cankers above the lowest living branch increased with tree size, suggesting that the infection court occurs on branches. With increasing tree size, cankers on branches originate farther away from the bole and fewer cankers cause mortality. Considerable variation existed in disease incidence and mortality among the clones and four sample locations

Resistance in Aspen to Hypoxylon Canker

Hypoxylon canker of aspen has many of the features of an ideal system for studying woody plant defense mechanisms against fungi. The primary hosts, trembling and European aspens (Populus tremuloides and P. tremula) occur over broad geographic areas of the northern hemisphere, providing an immense array of genetic and environmental diversity for the development of this system. Less commonly affected hosts such as P. grandidentata, P. trichocarpa, P. balsamifera, P. alba, and others provide a foundation of plant materials with different levels of resistance and susceptibility. The capacity to generate hybrids among these and other nonhost poplars further expands the foundations of test plant materials.

FIVE-YEAR SURVEY OF SCLERODERRIS CANKER IN YOUNG RED PINE PLANTATIONS

Thirteen permanent plots containing 5,245 red pine trees (1520 years) were surveyed each spring from 1978 to 1982 for Scleroderris canker. During this time, four of the plots had negative disease increase rates (-.04 to -.48; based upon percent trees infected) and three plots had negative rates (-.21 to -.39; based upon percent branches infected). Associated vegetational data were also collected and correlated with disease intensification. Positive correlations were found between amount of Spiraea cover and percent trees infected (R =.65 to.78; P <.01) and percent branches infected (R =.41 to.74; P <.08). Low correlations were found between disease rates and other associated vegetation. These data show the intensification of Gremmeniella abietina in these plantations has markedly decreased and some plantations are showing signs of recovery.

Disease Increase Rates for Scleroderris Canker in Lewis County, New York

Annual inspection, since 1975, of four permanent red pine plots provided a data base for calculating disease increase rates. Initial establishment of infection was estimated by projecting rate values back to first branch or first tree infected. Initial infection occurred within five years of plantation establishment and disease progressed to 90% infection within four to seven years of disease onset. These data show the extremely explosive potential forthe Scleroderris canker pathogen.