Galls caused by Meloidogyne chitwoodi are small and difficult to see. Meloidogyne hapla causes small distinct galls with proliferation of lateral roots around these galls. Meloidogyne incognita causes more pronounced galls. All three species of Meloidogyne and Pratylenchus penetrans cause bumps or warts on the surface of infected tubers. However, those caused by M. hapla are less distinct.
Lesion nematodes cause reddish brown lesions on the roots that turn black later.
To make management decisions, it is important to know the nematode species present and their population estimates. If a previous crop had problems caused by nematodes that are also listed as pests of potato, population levels may be high enough to cause damage to subsequent potato crops. If nematode species have not previously been identified, soil samples should be taken and sent to a diagnostic laboratory for identification. Take soil samples in fall from within the root zone of the previous crop after harvest or, preferably, just before harvest. Divide the field into sampling blocks of not more than five acres.