Yield is usually the top priority when selecting soybean varieties, but pests may also warrant consideration.
That's according to Bruce Potter, integrated pest management specialist with the University of Minnesota Extension Service. He describes some problems that deserve attention when choosing varieties:
- Iron chlorosis. Not actually a crop pest, iron chlorosis can be aggravated by root rots, soybean cyst nematodes (SCN) and herbicides. An iron chlorosis-tolerant variety with SCN or phytophthora root rot resistance may be needed. However, rating iron chlorosis tolerance is difficult, and ratings aren't standardized among companies.
- Phytophthora root rot. Genetic resistance is available through several Rps genes. But some races of the fungus can tolerate all current Rps resistance genes. Other races may develop resistance if the same Rps gene is used continually. So it's important to monitor the performance of phytophthora resistance genes, says Potter.
Some seed companies also rate varieties for their field tolerance to phytophthora. But tolerance usually isn't sufficient in severely infected fields.
- Fusarium and rhizoctonia root rots. No genetic resistance is available, but fungicide seed treatments may reduce their severity.
- Brown stem rot. This is often a problem with reduced tillage, and it tends to be more severe in non-rotated beans. Seed companies usually provide brown stem rot tolerance or resistance scores for their varieties.
- White mold. No genetic resistance is available, but many varieties have white mold tolerance scores. Avoid varieties with poor white mold scores in fields with a history or potential for the disease.
- SCN. More and more higher-yielding SCN-resistant varieties continue to be released. Consider using a resistant variety as soon as the pests are found in a field. Ignoring SCN can lead to high nematode populations, which can prevent even SCN-resistant varieties from yielding well.
SCN resistance carries a slight yield penalty. But look at resistant varieties as a long-term strategy designed to keep the field productive, says Potter.