Abstract
Eighteen cucurbit cultivars representing 5 genera, 9 species, and 11 taxa susceptible to gummy stem blight were inoculated with Didymella bryoniae in field plots in Charleston, SC, in autumn 2008, autumn 2009, and spring 2011 to determine the suitability of the hosts and various plant parts for formation of sexual and asexual fruiting bodies of the pathogen. In 1, 2, or 3 years, D. bryoniae reproduced on all 18 cultivars, on leaves, and on all plant parts examined—pedicles, peduncles, petioles, tendrils, and vines. Watermelon and citron (both Citrullus lanatus) and melon (Cucumis melo) had significantly more leaves with fruiting bodies than cucumber (Cucumis sativus), bottle gourd (Lagenaria siceraria), and eight cultivars of squash and pumpkin (Cucurbita maxima, C. moschata, and C. pepo). On plant parts other than leaves, melon had the greatest proportions of tissue pieces with fruiting bodies, and citron had the least. Fruiting bodies were observed on 86% of plant parts examined in autumn 2009 but on only 28% in spring 2011, when environmental conditions were hot and dry. In 2009, pseudothecia and pycnidia were found in equal proportions on leaves, but pseudothecia were found more frequently than pycnidia on leaves in 2011 and on other plant parts in 2009 and 2011.
