Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/16/2007
Publication Date: 4/1/2008
Citation: Oudemans, P., Polashock, J.J., Vinyard, B. 2008. Fairy Ring Disease of Cranberry: Assessment of Crop Losses and Impact on Cultivar Genotype. Plant Disease. 92:616-622. Interpretive Summary: Fairy ring is an important disease of cranberries in the eastern growing regions of the U.S., especially New Jersey and Massachusetts. Rings can persist for many years and fungicide control is costly and largely ineffective. Impact of the disease on crop production is not well documented. We used aerial imaging to determine that rings expand at a rate of 0.5-0.75 m in radius per year. Yield losses were determined by direct sampling and found to be 50%-70% less than unaffected areas of the bed. The vines within most cranberry varieties are genetically identical to each other and fruit morphology within rings was variable. When tested, we found the variety ‘Ben Lear’ to be genetically variable in diseased areas of the bed. We propose that this is due to establishment of seedlings as the variety in the bed is killed by the disease and seedlings are allowed to grow. The seedlings are likely to yield less than the parental variety and thus contribute to long term bed productivity. This information will lead to a better understanding of the impact of this disease and will be useful to researchers, extension agents and growers.
Technical Abstract: Fairy ring is a disease of cultivated cranberries common in the eastern growing regions of the U.S., especially New Jersey and Massachusetts. Rings may persist for many years and current recommendations are costly and largely ineffective. The goal of this study was to accurately assess the impact of fairy ring on cranberry, a long lived, high value, perennial crop. The rate of fairy ring expansion, rate of disease spread and the distribution of rings across three cultivars was determined using a geographical information system (GIS) data base that incorporated aerial and satellite imagery. Ring growth rates were estimated from satellite and aerial imagery collected over a ten year period and averaged an increase of 0.455 m in radius per year. Rings occurred on the cultivar Ben Lear with more than three times greater frequency than either ‘Early Black’ or ‘Stevens’ cultivars. Yield effects were determined by sampling berries from inside and outside of the rings. Yields within rings were 50%-70% less than unaffected areas of the bed for the cultivar Ben Lear. These estimates included the effects of fruit rot which was elevated within rings and ranged from 20%-70%. The impact on yield of ‘Stevens’ and ‘Early Black’ was lower than in ’Ben Lear. Most cranberry cultivars are clonal and variation in fruit morphology within rings prompted an analysis of vine genotype. Areas affected by fairy ring in the cultivar Ben Lear showed and increase in genetic diversity between two to four times that of unaffected areas. It appears therefore that fairy ring not only reduces yield but also increases the host genetic diversity. This is likely due to increased seedling establishment resulting from seed drop when fruit decompose. Since seedlings typically yield less than the parental cultivar, the increase in genetic diversity may also contribute to long term reduction of productivity in a cranberry field.