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Crabapples (Malus spp.) are popular ornamental trees in the commercial and residential landscape. Over a 33-year period at the Secrest Arboretum, Wooster, OH, 287 accessions of ornamental crabapple were evaluated for their resistance to apple scab caused by the fungus Venturia inaequalis. Of these 287 accessions, 31 had no symptoms of scab for longer than a 10-year period and were identified as resistant to the disease. Of these 31 resistant accessions, 14 eventually displayed symptoms, presumably as a result of infection by one or more newly present races of the pathogen in the trial plot. Notable resistance breakdowns in accessions previously classified as resistant include the development of scab on M. × ‘Prairifire’, M. × ‘Bob White’, M. × ‘Red Jewel’, and M. floribunda. Corresponding to these changes of resistance is the putative development of new V. inaequalis races in North America: Race 5, possessing virulence to the Vm gene in ‘Prairifire’; Race 3 that infects M. × ‘Geneva’ but not M. baccata ‘Dolgo’; and the first identification and report of scab on a M. floribunda population that was reported as resistant even before the first 25 years of the evaluation. The detection of scab on this species suggests the presence of Race 7 in North America for the first time. Five named accessions remained free from scab for the entire 33-year trial: M. sargentii ‘Sargent’, M. baccata ‘Jackii’, M. × ‘Beverly’, M. × ‘Silver Moon’, and M. × ‘White Angel’ and may serve as sources of durable resistance in crabapple and commercial apple breeding in the Midwest.
The Ohio State University (OSU) Extension Nursery, Landscape, and Turf Team (ENLTT) is an innovative and interdisciplinary team comprised of extension agents, extension specialists, researchers, teaching faculty, university arboretum staff, and research assistants. ENLTT has greatly improved the process of acquisition, delivery, and support of accurate, practical, and timely educational resources through interdisciplinary and industry partnerships. The award-winning weekly electronic newsletter Buckeye Yard and Garden Line (BYGL) has been the focal point of our teamwork since 1993. An ornamental research circular, authored and edited by ENLTT members, remains the most requested publication from the Section of Communication and Technology, Ohio Agricultural Research Development Center, OSU. Strong partnership with the green industry in Ohio has resulted in the financial commitment of more than $230,000 from the Ohio Nursery and Landscape Association since 1993. ENLTT members have improved themselves as a result of educating each other through weekly BYGL conference calls from April to October, taking study tours, and conducting joint educational programs. Twenty-two commodity or issue teams, such as, Floriculture Team, Vegetable Crops Team, Tree Fruit Team, Forestry Team, Agronomic Crops Team, Sustainable Agriculture Team, and Dairy Team, have been formed in OSU Extension due to the success of ENLTT.