Researchers look to combine practices to combat soil-borne diseases in dry beans

The unpredictable nature of soil-borne diseases in dry beans has challenged researchers at the University of Wyoming to test the efficacy of an integrated approach. 

Associate Professor in Plant Pathology Bill Stump explains the complications that come with controlling diseases such as rhizoctonia and fusarium root rot are due to the wide variety of practices and environmental factors. 

Causes 

According to Stump, there is not a single cause of these diseases but rather a variety of practices that together or independently can cause diseases. 

“Compaction can be a really big issue,” he says. “Think about how we might till the same place over and over and make the ground hard over time.” 

He explains the hardening of the ground can slow the growth of bean roots, therefore making them more susceptible to various diseases. 

Environmental conditions can also play a role in the severity of these diseases. He notes it can be hard to pin down a specific condition that makes the diseases worse, but  warmer, more moist conditions in the spring have been known to worsen the effects of many soil-borne diseases. 

Stump also explains how a lack of crop variety can cause issues. 

“Farmers need to be mindful of their crop variety,” he says. “If we’re growing the same beans every single year, there’s a higher likelihood of increased diseases.”

Implications 

Stump explains soil-borne diseases are very common, and farmers often only notice them when the infestations are very serious.

He explains the elastic nature of bean roots allows for them to recover quickly from such infections as rhizocotonia and fusarium. 

“These diseases can cause vascular issues, wilting and root rot,” according to Stump. 

According to a fact sheet published by Colorado State University (CSU) Extension, plants infected by fusarium root rot are rarely killed by the pathogen itself. Infected plants are generally scattered about the field, and above-ground symptoms can be difficult to see. Diseased areas of the plants will begin to enlarge and gradually turn brown.

CSU Extension notes rhizoctonia root rot also occurs in an irregular field pattern. 

Symptoms of the disease start at the root soon after planting and present as circular sunken lesions or cankers. These lesions can slow plant growth. 

Disease management

“There is no silver bullet when it comes to these issues,” Stump explains. “Our goal through new research is to determine if an integrated approach to managing these diseases will alleviate some of the associated issues.”

The research team plans to combine in-furrow fungicide at planting, varietal selection and deep tillage to protect the beans from the impacts of soil-borne diseases from planting to harvest. 

“We’re currently reviewing the chemical make-up of a variety of fungicides to determine which will work best,” Stump says. “We have had mixed results but are looking into anything that has even a mild benefit.” 

Stump notes most varieties of plants do not have resistance to such diseases, but there is a range of responses in the various varieties. He comments some varieties even had higher yields with the diseases. 

The team will also be utilizing deep tillage practices to loosen up the soil and prevent compaction issues. 

“At the end of the day, we just want to help producers determine what measures to take to alleviate the issues associated with soil-borne diseases,” Stump comments. “We hope we can help them choose the best cultivars, determine if deep tillage will be useful on their operations and prescribe the most effective in-furrow fungicide.”

Callie Hanson is the assistant editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.