They are generally considered to be mildly parasitic by most corn nematologists, but experimental data is lacking. These nematodes appear to be well adapted to our sandy soils and are occasionally seen in finer textured soils. They are known to be parasitic on corn in the field. Populations have been found exceeding 1,400, but most are in the 10 to 100 range. Populations above 300 to 400 have been associated with stunted corn in Iowa tests and should be considered economically threatening.
Lesion nematodes are common statewide.
Probably the most important nematodes attacking corn, population levels sometimes reach 3,000 to 5,000 by mid to late summer. Our experimental data indicate that counts of 1,000 are sufficient to cause a measurable yield depression of about 4 bushels per acre. However, this threshold level may vary considerably with soil, climate, hybrid, cultural practices, and stage of growth. Mid to late season counts of between 1,000 and 3,000 may be threatening, and treatment the following spring should be considered. Many species of stem nematodes are found in soil throughout the United States, but they are not commonly associated with corn.