The REAL Threat of Corn Nematode Injury in Northern Illinois
Department of Crop Sciences
The recent labeling and marketing of products intended for nematode management in corn in Illinois prompted interest in the occurrence, distribution, and population densities of corn-pathogenic nematodes. Jim Morrison and Dave Feltes, extension educators in northern Illinois, coordinated a study during 2008 of 19 northern Illinois counties in order to test protocols that will be used in a future study to include 80 additional counties, excluding those which are predominantly urban. For the 2008 study, eight cooperators were each assigned randomly-generated GPS coordinates along a pre-determined route in two to four counties per cooperator. A total of 76 soil samples were collected from corn fields at or near the assigned coordinates from corn plants at the V3 to V6 growth stage. Overall, the nematode communities were composed of about 50% bacterial-feeding and 50% plant parasitic nematodes. The most frequently (97%) occurring group of nematodes with stylets was the “tylenchids,” which may include fungal feeders as well as plant parasites. The second most frequent (94%) group was the spiral nematode complex, consisting mostly of Helicotylenchus species (Fig. 1). The most frequent (92%) genus of possibly corn-pathogenic nematodes was Pratylenchus (Fig. 2), including at least five species. Other genera of potential corn pathogens observed were Hoplolaimus (36%), Xiphinema (18%), and Paratylenchus (11%). The stunt nematode group was found in 24% of the samples, and comprises at least three species in two genera. Juveniles of Heterodera were observed in 57% of the samples. Species identification will provide additional insight into the potential for any or all of these groups or genera to reduce corn growth or yield (Fig. 3).