The Great Lakes have a lot of influence on the climates (and the agriculture) of the lands that border them, whether those lands are in New York or Michigan. That’s why a study conducted by members of the Michigan State University’s Department of Entomology may be of interest for those in the Empire State growing soybeans.

Conducting a “Survey of soybean management practices and their influence on soybean cyst nematode populations” were Razieh Yazdani, Ali Yaghoubi, Lance Forsberg and Marisol Quintanilla of MSU. They noted that plant-parasitic nematodes have been found to pose significant threats to soybean production, with soybean cyst nematode (SCN) remaining “the most economically damaging pathogen of soybean, causing substantial yield losses.”

This team completed a comprehensive survey across 11 Michigan counties in September and October 2023 to look at the incidence, abundance and diversity of plant-parasitic nematodes to evaluate the factors that influence SCN populations. They presented their findings at the most recent Great Lakes Expo.

The field history, including crop rotation practices, tillage methods, cover crop usage and nematode management strategies, was gathered from the farmers at each site. Unfortunately, eight different genera of plant-parasitic nematodes were identified from the 112 soil samples gathered. Heterodera glycines (SCN) was discovered in 87% of surveyed fields; Helicotylenchus in 86.6% of fields; Merlinius in 69.6% of fields; and Pratylenchus in 57.1% of fields.

H. glycines is the most devastating pest to soybean crop yields in the U.S., targeting the roots of soybean and other legume plants (such as dry bean, lupine, sweet clover and chickweed), according to the University of Missouri Extension. Severe SCN infection causes stunting, yellowing, impaired canopy development and yield loss in soybeans.

Helicotylenchus (spiral nematodes) can be found damaging crops as diverse as corn, bananas, grass and soybeans. Merlinius tends to affect sorghum and barley. Pratylenchus (lesion nematodes) also infest soybeans, potatoes, corn, bananas and wheat, but the genus is found most often in corn.

The survey unearthed some notable results. First, SCN populations were found to be significantly higher in sandy soils compared to other soil types. They were also much higher in continuous corn-soybean rotations vs. more diverse rotation systems.

Fields managed solely with resistance exhibited significantly higher SCN populations compared to those that implemented integrated approaches – combining crop rotation, cover crops and tillage made a difference. One particular approach – winter cover crops – was associated with reduced SCN populations.

“This study … emphasized the importance of integrated management strategies, including diverse crop rotations and cover crops, particularly in high-risk environments,” the researchers stated.

Soil Type Influence

SCN populations varied significantly among soil types. As previously mentioned, sandy soils had the highest populations (4,476 eggs per cubic centimeter), exceeding other soil types by a lot: muck (0 eggs), loamy sand (154 eggs), silt loam (206 eggs), loam (229 eggs), clay (462 eggs) and others (1,405 eggs).

The soil type for each site was determined by the USDA Web Soil Survey.

Crop Rotation Influence

It was also found that SCN populations were strongly impacted by crop rotation. Continuous corn-soybean rotations resulted in the highest SCN populations (4,042 eggs per cubic cm), significantly exceeding more diverse rotations like corn-soybean-wheat (1,435 eggs), corn-wheat-soybean-alfalfa (228 eggs), soybean-rye (154 eggs) and corn-soybean-alfalfa (66 eggs).

Cover Crop Influence

The survey found that winter cover crops were used by more than 46% of Michigan soybean farmers. They included oats, cereal rye, mustard, oilseed radish and clover. In good news, it seemed the radish-clover-oat rotation resulted in complete SCN suppression (0 eggs), significantly outperforming the radish-rye-clover-mustard rotation (2,242 eggs).

While most cover crop rotations reduced SCN populations compared to fields without cover crops, these reductions were not statistically significant – except for the radish-cover-oat rotation.

Management Practices Influence

A total of 100% of the beans planted were resistant soybean varieties, but the research survey found that integrating additional management practices reduced SCN populations significantly.

The fields managed only with resistant varieties had the highest SCN populations (6,487 eggs), whereas combinations – such as crop rotation-cover crops-resistant varieties (562 eggs) and other integrated strategies – showed significantly lower SCN populations.

While Michigan and New York aren’t identical when it comes to growing soybeans, the lessons learned by Wolverine State farmers may be useful to those farther east.

by Courtney Llewellyn