After harvest this fall will provide growers with the best opportunity to check fields for the soybean cyst nematode. That's according to Iowa State University Plant Pathologist Greg Tylka. He says growers will know how their crop yielded, and will have an easier time collecting a good sample when there's no crop in the field.
"It's really easy to zig zag your way through a field and collect 20 soil cores from every 20 acres or so," Tylka said. "It's much, much more difficult to do that when there is a standing soybean crop or standing corn crop. Some people might say why would you sample a corn crop for soybean cyst nematode, but a lot of those fields that had corn during the 2011 growing season will be planted to soybeans the following year, so you would want to sample fields that had corn in this growing season to get ready for next growing season."
Another benefit to fall sampling, Tylka says, is time. Once samples are submitted and growers receive the results, he says they have more time to consider their management options.
"You can decide if you want to grow a resistant variety, you can decide if you need to switch to another year of corn to get your egg numbers down, you can contemplate using one of the new seed treatments that are on the market," Tylka said. "You have really that whole fall and winter timeframe to do that. You can sample in the spring, but everything is compressed at that point and you don't have a whole lot of time to think about what your options are."
When it comes to the soybean cyst nematode, Tylka says knowledge is power. Unfortunately, Tylka says many fields have not been tested for the pest. He advises all growers in the Midwest planning to plant soybeans in 2012 to sample this fall to see if SCN is in the field. He says it will definitely be worth it.
"That simple soil sample taken this fall could save them five, 10, 15, 20 bushels per acre," Tylka said. "If they discover that the field is infested, there are literally hundreds and hundreds of SCN resistant soybean varieties that could be planted in that field in the 2012 growing season. But is all starts with knowledge about whether or not that field has soybean cyst nematode."
For growers who have tested, know they have SCN and have managed the problem with resistant varieties, Tylka still suggests sampling this fall. He says SCN resistant soybean varieties are a great management tool, but because most of them share the same resistant gene over time development of resistance to the resistance is a concern. By sampling and looking at egg numbers Tylka says growers can determine if the nematode is adapting and building the ability to reproduce on resistant varieties.
Tylka says the only way to know if egg counts are creeping up again is to collect a good soil sample in the fall. It is also important to note as growers head into harvest that farm machinery, vehicles, tools, wind, water, animals and farm workers are all capable of spreading SCN. And once the soybean cyst nematode is present in the soil, it can never be eliminated, just managed.