Fruit Disease is one of the Most Destructive in the World

Monday, August 10, 2020

UNH graduate student Liza DeGenring is investigating the development of new tools to manage apple scab for Northeast farmers.

University of New Hampshire researchers have teamed up with colleagues from Pennsylvania State University to investigate whether a byproduct of the seafood industry could help

Fruit trees grow in the UNH Macfarlane Research

manage one of the most devastating fruit diseases facing the U.S. apple industry.

UNH graduate student Liza DeGenring is investigating the development of new tools to manage apple scab for Northeast farmers. Specifically, she is investigating the combination of beneficial microbes with a natural compound called chitosan—a byproduct of mostly shrimp shells from the seafood industry.

Many beneficial microorganisms associated with plants have been commercialized and sold as biopesticides for use in agriculture to reduce plant diseases. The tree fruit industry has begun adopting these alternative tools with some success. These products include Serenade ASO and Double Nickel 55, both of which rely on beneficial bacteria. Widespread adoption of biopesticides, however, has been limited due to inconsistencies in their effectiveness.

“Because biopesticides are living products, their activity is affected by environment. Biopesticides often fail to grow and maintain high enough population levels in the orchard or do not produce antifungal compounds at levels necessary to suppress the disease. It is increasingly recognized that solving these issues is key to increasing adoption of biopesticides. I am investigating a way to enhance biopesticide effectiveness using chitosan. There is evidence that chitosan may act as a food source for the biopesticides and stimulate production of antifungal enzymes, thereby enhancing their usefulness,” she said.

Much of the research around chitosan has focused on the reduction of postharvest disease—once the fruit or vegetable has been harvested. Chitosan has shown to be effective in reducing plant disease and preserving fruits and vegetables during storage and transport. Researchers at UNH would like to extend this research to investigate the effect of a chitosan application during crop production and in combination with an application of biopesticides.

DeGenring is working with NH Agricultural Experiment Station researcher Anissa Poleatewich, assistant professor of plant pathology and her faculty advisor. Collaborators include George Hamilton and Jeremy DeLise, both with UNH Cooperative Extension, and Kari Peter at the Pennsylvania State University Fruit Research and Extension Center.

“Reduced fruit quality is a major concern for the New Hampshire tree fruit industry since NH growers primarily market retail sales of fresh apples through pick-your-own, farm stands, and direct sales to grocery stores. Apple scab lesions on the fruit can result in decreased revenue to the grower due to consumers’ low threshold for imperfections on their apples,” DeGenring said.

Apple scab, caused by the fungus Venturia inaequalis, is one of the most destructive diseases of apple worldwide. This disease is a significant threat to growers in the Northeastern United States because of the warm, moist conditions during the growing season that favor disease development. Apple scab can cause up to 100 percent crop loss and significant reduction in fruit marketability. According to the USDA National Agricultural Statistics Service, the market value of apples nationwide was $2.4 billion. The New Hampshire tree fruit industry includes 228 farms growing 1,701 acres of tree fruit, valued at $9.3 million.

MacIntosh and Golden Delicious seedlings in the growth room at the                   
UNH Macfarlane Research Greenhouse.

According to Poleatewich, apple growers in New England and the Potomac states have been battling apple scab and fireblight for decades. These diseases are more problematic in the Northeast than the Pacific Northwest due to the Northeast’s warm, wet climate that favors disease outbreaks.

“UNH has a historical reputation of conducting apple scab research. Much of what we know today about the disease is based on work done by William MacHardy, professor emeritus of plant biology. New Hampshire tree fruit growers have a strong history of collaboration with UNH to develop and adopt more environmentally and economically sustainable practices. In the 1980s, MacHardy and colleagues developed disease-forecasting models that growers still use today to predict outbreaks and apply fungicides only when disease risk is high. New Hampshire growers also have adopted Integrated Pest Management, which incorporates cultural, biological, and chemical practices to suppress disease. Even with these advances, apple scab continues to be a major nemesis to tree fruit growers,” Poleatewich said.

To combat apple scab disease, growers primarily rely on sanitation and fungicide applications in their orchards. However, there is increasing pressure by consumers to decrease the use of synthetic chemicals due to concerns of adverse effects on nonpest species and human health, as well as the risk of pathogen resistance development with regular fungicide applications. Both the potential decrease in consumer demand and increased costs of resistant pathogen management can decrease producer profits.

“Both farmers and apple consumers would like alternative options for controlling apple scab. Chitosan has shown promise in other research in reducing disease, and there is a potential to use it to suppress disease in tree fruit production,” DeGenring said.

According to DeGenring, the success of sustainable agriculture in the United States will increasingly rely on the integration of biologically based methods with conventional agricultural practices that rely on fungicides. The scientific and agricultural community has begun to recognize the critical role microorganisms, such as bacteria and fungi, and their metabolites play in agroecosystem health.

This material is based upon work supported by the NH Agricultural Experiment Station, through joint funding of the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 1016530, and the state of New Hampshire. This work is also funded by a Northeast Graduate Student USDA Sustainable Agriculture Research and Education grant and a New Hampshire Specialty Crop Block grant.

Founded in 1887, the NH Agricultural Experiment Station at the UNH College of Life Sciences and Agriculture is UNH’s original research center and an elemental component of New Hampshire's land-grant university heritage and mission. We steward federal and state funding, including support from the USDA National Institute of Food and Agriculture, to provide unbiased and objective research concerning diverse aspects of sustainable agriculture and foods, aquaculture, forest management, and related wildlife, natural resources and rural community topics. We maintain the Woodman and Kingman agronomy and horticultural research farms, the Macfarlane Research Greenhouses, the Fairchild Dairy Teaching and Research Center, and the Organic Dairy Research Farm. Additional properties also provide forage, forests and woodlands in direct support to research, teaching, and outreach.

The University of New Hampshire is a flagship research university that inspires innovation and transforms lives in our state, nation and world. More than 16,000 students from all 50 states and 71 countries engage with an award-winning faculty in top ranked programs in business, engineering, law, liberal arts and the sciences across more than 200 programs of study. UNH’s research portfolio includes partnerships with NASA, NOAA, NSF and NIH, receiving more than $100 million in competitive external funding every year to further explore and define the frontiers of land, sea and space.