So, if you suspect corn nematode problems or want to see if they are present, sample early in the season. Both dagger and needle nematode populations seem to produce one or, at most, two generations per year. Some juveniles of the needle and both juveniles and adults of dagger nematode were detected in August and September of 1996, but at very low populations. Very few were found this late in 1995. These late populations seem to depend on the weather and lateness of the crop.
Crop rotation is important because corn nematodes are grass feeders.
Needle nematode populations will drop rapidly with a single year of soybeans, but dagger populations may remain somewhat higher. However, two years of corn generally result in very high populations that cause extensive damage. Neither has the needle nematode listed on the label. No company will guarantee to control pest populations down to fewer than five individuals per sampling unit. If a nematicide is used, it can still provide protection against other nematodes for which it is labeled and help reduce stress from these pests.