Don't look now, but just when you think you've got soybean cyst nematode problems figured out, the pest may be ready to make your life miserable again. Some agronomists think the silent thief that works quietly behind the scenes is already well on the way to doing so. Purdue University nematologists say that the most common form of resistance included in most commercially nematode-resistant soybean varieties today is beginning to demonstrate chinks in the armor- more so each year. Put differently, nematodes are breaking through and causing more damage on those varieties than when that form of resistance was first introduced commercially.
The form of resistance used in about 97% of today's commercial varieties is PI 88788, Purdue sources say. Even the Purdue researchers have noticed it hasn't been performing as well in general recently.
Whether it's a problem for you may depend partly upon whether you have serious nematode problems in your fields. The only way to know for sure is to pull nematode samples and send them for analysis, says Jeff Nagel, Ceres Solutions, West Lafayette, Ind. Nagel is a member of the Indiana Certified Crops Agronomists organization.
Samples can be pulled anytime during the year, Nagel says. He recommends pulling cores with a soil probe, or suing a trowel. You want soil from four to eight inches deep fro analysis. Mix soil form these cores into one sample to send to the lab. Nagel prefers that one sample represent no more than 20 acres.
The Purdue University Nematology Lab can analyze samples. Cost is $10 per sample. Lab officials say number of samples run per year are down drastically compared to a few years ago. That's likely partly because the Indiana Soybean Board paid for 10 samples per producer per year for several years, but discontinued the program a couple years ago. Just because they no longer pay for samples doesn't mean that nematodes aren't still a threat.
In fact, Andy Awald, Farmers Fertilizer & Seed, Hamlet, believes soybean cyst nematode is the biggest pest threat to soybeans that's come along so far,. He also encourages sampling to know where you stand on test levels.
Cyst-X soybean resistance developed at Purdue a few years ago was licensed for commercial development, and is available in some commercial varieties. However, Nagel notes that it is not being widely used. When planted where there are no cyst problems, Cyst-X varieties don't always yield up to par with other elite varieties that don't have cyst resistance, he notes.
Pioneer Hi-Bred International, Inc., recently announced plans to introduce four new cyst-nematode resistant varieties for '08. According to spokespersons for Pioneer, these varieties have different forms of resistance than what's currently on the market. At least some of them use the Peking resistance to nematodes.
The only drawback for Indiana producers is that most of the new Pioneer releases are for very early maturity ranges, including Group 0, Group I and early Group II. However, one of the new releases is positioned as a mid-Group III variety, which should be adaptable across a good share of the central Corn Belt.