Nematodes generally do not cause damage to maize plants unless they occur in large numbers and other factors impair root development. Symptoms of damage vary by nematode species. For example, Pratylenchus species cause delayed growth in patches and yellowing of the leaves, with significantly reduced root mass showing dark necrotic discoloration. The stalk aphid (Ditylenchus dipsaci) causes stunted, curved corn stalks, resulting in unstable plants. Heterodera species cause stunted growth and sometimes plant death. The necrotic areas on the roots can spread further through other soil-borne pathogens, leading to further damage and plant loss.
Nematodes are soil-borne organisms that attack maize via the roots. The adults reproduce in the bark tissue (Pratylenchus spp. and Ditylenchus dipsaci), or larvae from cysts penetrate the roots (Heterodera). There is no specific time period for nematode occurrence, but damage is typically visible in spring and can continue throughout the year. A cool, damp climate promotes nematode activity.
There is no established damage threshold to predict the extent of damage.
Chemical control of nematodes is not possible. Indirect control can be achieved by cultivating nematode-resistant catch crops as part of an intact crop rotation. Additionally, controlling weeds that serve as host plants can help. Promoting rapid juvenile development of maize also reduces damage from nematodes.