TWIN FALLS — When farmers hear the word nematode, their hearts often sink.
While these microscopic worms can help break down crop residue and recycle nutrients, they have a bad reputation for feeding on crop roots, thereby reducing yields and quality. Idaho potato growers lost valuable export markets for years after potato cyst nematode was found here in 2006.
That’s why the seed bean industry has been so concerned about growing interest to raise soybeans to feed Idaho’s dairy cows. With soybeans comes the potential for soybean cyst nematode and the loss of valuable export markets.
Soybean cyst nematode interferes with nodulation on legumes and can cause early yellowing and stunting. Soybean growers have seen losses of 10 to 70 percent from the nematode.
Soybeans, common beans and alfalfa are all hosts for the soybean cyst nematode. Several studies have also indicated that sugar beets can be a host for the soybean cyst nematode. Studies dating back to 1965 have shown that if both nematode species are present in a field, they can mate and the progeny will survive on both sugar beets and bean plants.
That’s the scariest aspect, for bean growers like Bill Bitzenburg, who farms south of Twin Falls. “I’m afraid that if we have soybean cyst nematode, we won’t be able to export bean seed.”
Although soybeans are included in the state’s bean quarantine law and it is not legal to bring them into Idaho from regions east of the Continental Divide. However, some cover crop mixes that are purchased from out-of-state dealers have included soybeans and a couple hundred acres of feed soybeans were grown in the Magic Valley in 2017.
The Idaho Bean Commission worked with Idaho legislators in 2018 to strengthen the bean quarantine law, but those efforts were unsuccessful. So the Bean Commission is taking a different approach — develop a nematode-free seed source within the state.
Eric Jemmett, of Jemmett Consulting and Research in Parma, worked with the Idaho Bean Commission and Idaho State Department of Agriculture to bring in six soybean varieties for testing during 2018. The first hurdle was getting the seeds through the nematode and serology testing.
Jemmett had hoped to plant by the middle of April, but the serology tests took 90 days and so planting was delayed until June 1. That delay hurt yields. His highest yielding variety produced just 34.91 bushels per acre compared to average Midwestern soybean yields of 60 to 74 bushels per acre.
He also learned that yield and quality are correlated, and that higher yielding varieties often have lower protein levels, which largely determines quality. Livestock feeders require at least 40 percent protein. Even though his yields were low, protein also was in 2018. Jemmett thinks that is because soybeans are triggered by the summer solstice to switch from vegetative growth to setting seed. With only about three weeks between planting and the summer solstice, the plants were just too small to have a good crop.
However, Jemmett believes the crop can do well in Idaho.
“Soybeans can work here,” he said during the University of Idaho Bean School. But finding seed remains an issue. “You must get seed from an ISDA approved seed source. Seed cannot be brought in from outside sources.”
Jemmett and the Bean Commission are working with the State Agriculture Department to develop seed stocks within Idaho to fulfill that demand. Jemmett thinks there might be seed available by 2020.
In the meantime, the Idaho Crop Improvement Association is developing rules that will govern the time interval between growing soybeans and seed beans within the same field.
“We do not want to introduce soybean cyst nematode,” Jemmett said. “That will make it impossible to grow seed beans here.”