Update:
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Research conducted
The experiment was conducted in Prosper and Casselton in 2018, to determine the effect of preceding and interseeding cover crops into SCN-susceptible and SCN-resistant soybean on soil with high SCN populations. Winter camelina cv. Joelle, brown mustard Mighty Mustardâ„¢ cv. Kodiak, and crambe cv. Westhope were planted before soybean or interseeded at V6 stage. A check plot (no cover crop) of each variety was included.
Why the research is important to ND soybean farmers
Soybean cyst nematode (Heterodera glycines) is the most important pest in soybean causing over a billion dollars in losses in the US every year. Many farmers do not know they have SCN in their fields and 15-30% of soybean yield can be lost without any evident aboveground symptoms in the soybean. One of the main control practices for SCN is the use of resistant varieties; however, the resistance is breaking and most soybean varieties in ND have the same source of resistance. Cover crops preceding soybean planting or interseeded into standing soybean are becoming more common in corn-soybean systems in ND and as many are non-host crops, they are a potential option to manage SCN.
Final findings of the research
Cover crops (preceded or interseeded) did not significantly decreased SCN population at both locations. SCN populations increased in the susceptible variety in almost all treatments, while they decreased in the resistant variety. However, camelina interseeded at V6 stage of soybean was able to reduce SCN population in 32% at Prosper across both varieties. The uneven distribution of the SCN population in the soil made it very difficult to detect significant differences and replicate the positive results observed in greenhouse studies with camelina and mustard. The soybean yield in the susceptible variety averaged across all treatments was significantly lower than the resistant variety.
Benefits/Recommendations to North Dakota soybean farmers and industry
In spite of not finding significant results, we believe non-host cover crops interseeded into soybean have the potential to be an additional tool to manage SCN population, however more research is needed. The study will be repeated in 2019.
We recommend farmers to continue using the current management recommendations in fields with SCN such as rotation with non-host crops and SCN resistant varieties. At this point, we cannot recommend interseeding camelina, mustard or crambe as a tool to reduce SCN.