Delaware is second only to California in production of lima beans. USDA awarded the University of Delaware (UD) a five-year, $1.5 million Specialty Crop Research Initiative grant to study the impact of various diseases on the crop in Delaware and throughout the mid-Atlantic region.
Researchers from UD, Delaware State University, the University of Maryland, The Ohio State University, Cornell University, and University of California-Davis (UC Davis) will study downy mildew, pod blight, white mold, root knot nematodes, and germplasm resources, and will develop an economic analysis.
Downy mildew is a fungal-like disease caused by Phytophthora phaseoli. The goal of the research team, comprised of Tom Evans and Nicole Donofrio, professors of plant pathology in the Department of Plant and Soil Sciences in UD’s College of Agriculture and Natural Resources, and Nancy Gregory, plant diagnostician for UD; is to improve disease forecasting and look at genetic diversity of the population of the pathogen.
Pod blight is caused by the pathogen known as P. capsici and has a very wide host range. Once it strikes a particular crop, it is very difficult to get rid of, with pathogen spores lasting up to 10 years in the soil. Pod blight is an increasing problem for growers, occurs in low-lying areas of fields, and is more frequent in wet years. Researchers, including Gordon Johnson, assistant professor of plant and soil sciences at UD, with Evans and Gregory, will look for a fungicide to combat with the disease and look for alternative or organic non-pesticide driven options for control.
The study is also looking at risk management, including information for growers about the best time to spray for disease control and consideration of alternate control strategies.
Kate Everts, an adjunct associate professor of plant and soil sciences at UD and a Cooperative Extension specialist with both UD and the University of Maryland, is leading research on alternative ways to control white mold.
With a broader host range than P. capsici, and an even longer life — persisting in soils for 20-30 years — white mold is another disease that is very difficult to eliminate.
Everts will test biological control strategies and alternative control options for dealing with white mold.
Root Knot Nematodes
Johnson and Emmalea Ernest, a cooperative Extension associate in plant and soil sciences and plant breeder, will lead research on root knot nematodes. Researchers will screen new germplasm for resistance and look at how it impacts root knot in Delaware.
Paul Gepts, a research collaborator at UC Davis, will evaluate whether cultivars that are resistant to root knot nematodes in California are effective in Delaware, with the hopes of breeding nematode-resistant lima bean varieties.
The second part of this research is to use local weather and soil condition data ‑ such as depth and length of freeze, soil temperature ranges and soil moisture ‑ to help determine what types of conditions root knot nematodes thrive in. They will also be evaluating different assay methods to improve detection of root knot nematodes.
The researchers will use this environmental data and soil type to predict when and where the nematodes are likely to be a problem and develop root knot risk field assessment guides for growers.
For more on the research, click on the additional page.