Issue No. 4, Article 5/April 21, 2006
Time to Sample for Corn Nematodes
In Illinois, when most people speak of "corn nematodes," they're talking about the needle nematode, whichcan cause severe damage and even kill seedlings. However, corn nematodes come in lots of different shapes, sizes, feeding habits, and propensities for damaging corn. In addition to needle nematode, three other corn nematodes are commonly associated with corn injury in Illinois: lesion, dagger, and lance nematodes. Many other nematodes can damage corn but are more limited in distribution. For lots of good information, start with the University of Nebraska Web site.
Nematodes do not cause specific symptoms on corn. The injury caused by nematodes, to both roots and shoots, can be very similar to that caused by nutrient deficiencies, soil compaction, root rots, herbicide carryover, and other problems. The only way to diagnose nematode problems in corn is through soil samples analyzed by a qualified nematode testing lab. Many private labs test for corn nematodes, as does the University of Illinois Plant Clinic.
There is a common view that corn nematodes are only important in very sandy soils. This is not true for most corn nematodes. We have found two characteristics that increase the likelihood of a corn nematode problem: use of no-till practices and continuous corn planting. Poor or uneven crop development in no-till fields planted continuously to corn should be sampled for nematodes.
The best time to sample for nematodes in corn is in the spring, especially if you suspect needle nematode. For instructions on how to collect the best samples, see RPD 1100. Nematodes are typically the last thing on the list of things to check as the cause of corn development problems. That's understandable, because nematodes don't cause specific symptoms and they're hard to check for. Corn nematode control depends on the nematode species involved and how high the numbers are, so it's very important to get a reliable diagnosis.
Effects of corn nematode in northern Illinois (photo courtesy of Tamra Jackson).
For further information, contact me at (217)244-5940 or firstname.lastname@example.org.--Terry Niblack