Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Research Notes
Publication Acceptance Date: 2/16/1998
Publication Date: N/A
Interpretive Summary: Vegetable growers in the southeastern U.S. traditionally produce collard and kale during the cooler months of the year. However, to expand their production of these crops throughout the year, producers are trying to grow collard and kale during the hot summer months. As a consequence, their summer plantings are being infected with a hot weather disease called Fusarium yellows that is caused by a fungus, and they are suffering economic losses in these plantings. Cooperative research between Clemson University and ARS has shown that different varieties of collard respond differently when grown during the summer in a field containing a high level of the Fusarium fungus. Some varieties of collard appear to be resistant to yellows, show no signs of the disease, and produce normal yields. Other varieties are susceptible, become infected, and are almost totally destroyed by the disease. All varieties of kale that were tested were highly susceptible to Fusarium yellows. This research provides collard producers with valuable information and indicates that collard can be produced during summer without becoming infected with Fusarium yellows as long as producers choose a variety of collard not susceptible to the disease. On the other hand, it shows that producers take a great risk in growing kale during summer since all varieties are susceptible.
Technical Abstract: Collard and kale (both Brassica oleracea L.) cultivars were grown in soil naturally infested with Fusarium oxysporum f. sp. conglutinans and the incidence of the wilt disease, yellows, was evaluated. The objective was to determine if any collard or kale cultivars exhibited resistance to yellows similar to cabbage cultivars with documented resistance. Seventeen collard, five kale, two cabbage, and two broccoli cultivars were evaluated in this study. The experiment was conducted in a grower's field in Lexington County, South Carolina. The experiment had a completely random design with each cultivar entry replicated five times. Transplants were set in the field 19 June, 1997 and symptoms of yellows were evaluated visually 35, 53 and 71 days after transplanting. Disease pressure was sufficient to detect differences among susceptible and resistant cultivars. Most plants of both resistant cabbage cultivars remained symptomless throughout the study, despite high soil temperatures (ca. 95C). Four of the five kale cultivars were highly susceptible to yellows. Only two collard cultivars, Georgia and Georgia Southern, were highly susceptible in this test. Other collard entries were moderately susceptible with 22-29% disease incidence (DI), moderately resistant (17-21% DI), or as resistant as the cabbage cultivar Bravo (DI<13%). The most resistant collard cultivars were Flash, Heavicrop, HiCrop and Morris Heading. Use of one of these resistant cultivars should reduce the potential damage that can be caused when an outbreak of Fusarium yellows occurs in collard production.