Black knot disease of chokecherries, induced by Dibotryon morbosum (Schw.) Th. & Syd., is widely distributed in Utah. The incidence of black knot was measured by determining the ratio of total black knot gall length to total stem length of plants and then expressing that value as a percentage of diseased stems in the sample plot. The environmental site factors measured were elevation, exposure, slope, soil pH, soil depth, distance to surface water, plant moisture stress, and associated vegetation. Numerical values were determined for each of these variables at each of 18 randomly located plots. Correlation coefficients for plant moisture stress and soil temperature were −.439 (p = .065) and −.440 (p = .055). Multiple regression analyses using plant moisture stress and soil temperature gave a regression coefficient of −.641 (p = .05). As plant moisture stress and soil temperature decreased, incidence of black knot increased.
Stewart, Sarah Ann and Weber, D. J.
"Environmental site characteristics and incidence of chokecherry black knot in Utah,"
Great Basin Naturalist: Vol. 44
, Article 6.
Available at: http://scholarsarchive.byu.edu/gbn/vol44/iss4/6