Pest Management Progress For Soybeans

In this article, I will present some up-to-date research results that may lead to soybean farming tools that can be used to reduce losses caused by two of the major pests–soybean cyst nematode (SCN) and charcoal rot–identified in the above-cited reference.
SCN. This is the number one yield-limiting pest in US soybeans.

In a recent article in Agronomy Journal, scientists in Iowa and Wisconsin report results from a three-year study that was conducted to measure soybean yield response to rotation, tillage, and sources of genetic resistance to SCN.

They concluded that crop rotation (e.g. soybeans with corn) and source of genetic resistance are the most important soybean farming tools for managing potentially yield-limiting populations of SCN. They also concluded that the rotation advantage can be quickly negated if source of genetic resistance to SCN and knowledge of the HG-type (race) in a field is not considered.

The latter finding is probably the most important; i.e., rotation should be combined with the knowledge of HG-type present in a field so that source of genetic resistance can be selected when choosing a variety for that field. (In a forthcoming article, I will attempt to relate the HG-type concept to SCN race).

These results confirm the information presented in an article on this website, where we stated that relying on one source of genetic resistance can lead to reproduction of SCN in soybean fields that previously may have had a below-threshold population. This concept is similar to that of considering the MOA of herbicides when developing a strategy for weed management in order to prevent or delay the selection for herbicide resistance in weed species.
Charcoal rot. Currently, there are no commercial soybean varieties that are resistant to charcoal rot nor are there any fungicides that effectively control it. Thus, there are essentially no effective soybean farming tools for managing this disease.

Recently, scientists in the midsouthern US evaluated soybean genotypes in MG’s III, IV, and V over a three-year period to test for reaction to artificial infestations of the organism that causes this disease. In a recent article in Plant Health Progress, they report the results from those tests.

There was significant variation among the tested genotypes for reaction to the charcoal rot pathogen, but there was no genotype that was consistently immune to the pathogen every year.

On a more positive note, the scientists did identify six genotypes (one in MG III, one in MG IV, and four in MG V) that were moderately resistant to the charcoal rot fungus. They conclude that these genotypes could be useful as sources for developing soybean varieties that are resistant to the charcoal rot fungus.

Hopefully, the results from this research will provide the impetus for just such an accomplishment.
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larryheatherly@bellsouth.net.