Research Highlights

Research Highlights
Visualizing Nematode Damage with Planter Boxes

The number, size and development of soybean pods from plants grown in rhizoboxes with soybean cyst nematode (left), root-knot nematode (center) and no nematodes (right). Photo: Alyssa Koehler

By Laura Temple

Multiple species of nematodes feast on soybean roots in Delaware’s sandy soils. Alyssa Koehler, assistant professor and extension specialist in plant pathology at the University of Delaware, believes farmers will better understand nematode damage and management options when they see the impact of these pests. 

Thanks to soy checkoff support from the Delaware Soybean Board, Koehler began leading practical research in 2022 to show farmers the cost of nematode pressure and to explore interactions between common nematode species and cover crops.

“So far, we just have preliminary observations,” she says. “But our efforts to visualize economic nematode damage are very promising.”

Rhizoboxes Reveal Root Damage

Koehler considers visualization a valuable extension tool for education.

“It’s difficult to show farmers the symptoms and results of many types of nematode pressure,” she explains. “Species of root-knot nematodes cause visible galls on roots, but it is hard to show the stunting caused by soybean cyst nematodes.”

Soybean roots expanding to the bottom of a soybean rhizobox. Photo: Alyssa Koehler

Her lab team built rhizoboxes, or planter boxes with a clear plexiglass front, so farmers can see how SCN, RKN, lesion nematodes and species combinations impact soybean roots. The soil in the boxes can be inoculated with known concentrations of nematodes. The controlled environment simplifies the study of plant symptoms and yield loss.

Koehler’s team plans to make smaller rhizoboxes in the future to make it easier to include them in demonstrations and field days. However, the initial boxes allowed them to see differences in root growth, pod size and soybean yield caused by nematodes.

“With these rhizoboxes, we can reinforce to farmers the importance of soil testing and understanding nematode pressure,” she adds. “Seeing the cost of nematode pressure will encourage them to be intentional about managing against them.”

Nematode Interaction with Cover Crops

Koehler notes that research from other parts of the country has shown certain types of cover crops can suppress SCN population densities. 

“Many farmers in Delaware and this region use cover crops,” she says. “Do those cover crops help or hinder nematode management with our complex, multi-species populations?”

Growth of soybean plants and roots inoculated with soybean cyst nematode (left), root-knot nematode (center) and no nematodes (right). Photo: Alyssa Koehler

She took advantage of plots from a cover crop and slug pressure study funded by the Delaware Soybean Board to set a baseline and address this question. On-farm plots included cover crops of barley, rye and crimson clover, as well as no cover. The cooperating farmer has a history of nematode pressure in his fields.

“When we sampled for nematodes in late May before planting, we were surprised to find no SCN or RKN pressure,” Koehler reports. “All plots contained lance nematode, but at a low population level.”

Her team sampled the plots again in October, following the soybean crop, but observed no difference in nematode population.  

“We plan to repeat this trial in the future, when we can take advantage of field mapping and long-term cover crop research to ensure we sample fields with high nematode pressure,” she says. “We know small grains like ryegrass are a non-host for SCN. In a field with heavy pressure, we should get better data to help us learn if cover crops make a difference in nematode populations in our soils.”

Other Resources

Identifying and Managing Nematodes in the Atlantic Region – SRIN article

Research Supports 70 Years of Progress in the Fight Against Soybean Cyst Nematode – SRIN article

Alyssa Koehler profile

Published: Sep 5, 2023

The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.