by Greg LaBarge, Fulton County
Over the past 15 years, soybean cyst nematode have been something we have managed for in parts of northwest Ohio using rotation and resistant varieties in combination with testing to reduce population to minimize their impact on yield. “Corn nematodes” have become a topic of interest due to changes in production practices and surveys have shown higher population than previously know of in the state of Illinois. The buzz has caused questions about any effects here in Ohio plus the availability of seed treatment which control these nematode species have added to questions on this potential problem.
First we need to recognize “corn nematodes” are different from soybean cyst nematode in a big way. SCN is a single species while “corn nematodes” are actually a list of 28 species with 10-12 species considered important. The list at the right shows the common species of concern and sample levels associated with each. Some species are of greater concern and have a lower threshold while we can tolerate higher number of other species.
Another important difference is these multiple species feed on corn roots in two ways. Some are called ectoparasites which live in the soil and feed on the outer root surface while others are internal feeders called endoparasites. This affects the way we sample for “corn nematodes”. Soil samples similar to those used for evaluating SCN can be used with ectoparasite types while the endoparasites require sending root samples to the lab. So sampling during the growing season when corn is in the early vegetative stages is recommended sending in both a soil and plant sample.
Symptoms of “corn nematode” include stunted plants with off color, thinned stand, unevenness in plant development, and early maturation. Roots especially feeder root can show a proliferation of fibrous roots, appear thickened or swollen or have slight to sever discoloration.
Iowa State has a good Certified Crop Advisor Module on corn nematodes on-line at http://www.cai.iastate.edu/. Quick facts on corn nematodes can be found at http://www.extension.iastate.edu/CropNews/2009/0429tylka.htm. Results of the Illinois State Survey can be found at http://agronomyday.cropsci.illinois.edu/2010/tours/b2nema/.
We plan to locally sample some sights to check for populations of “corn nematodes” in 2011. If you have a suspect field let me know firstname.lastname@example.org or 419-337-9210 this summer.