Nematodes are simple, worm-like parasites that come in friendly varieties as well as pathogenic types that attack plants. These nematodes cause diseases by attacking all parts of the plant, including stems, leaves, flower blossoms and roots. Nematodes attack with mouths called "stylets" that stab through plant tissue, causing disease infection of a variety of plants.
Root Knot Nematode
Root knot nematodes (Meloidogyne species) create the disease of plants referred to as "root knot." Caused by over 40 different species, root knot consists of swelled areas called galls on roots and parts of plants that live underground in soil. Less established plants may display stunted growth, problems from drought and incapability of absorbing enough nutrients, according to the Ohio State University Extension. Root knots, or galls, may show up individually or in groups, attacking feeding roots. When feeder roots are under attack, plants cannot receive the proper water and nutrients they need for survival and may die. For control, rotate crops at a minimum of three years with crops unaffected by root knot nematodes. Make sure the plants you grow are clean and not already affected by nematodes. Look for resistant varieties. Though fungicides are not recommended for home use, they are often used in larger growth such as commercial production. Contact your local county extension agent for fungicide application information.
Lesion nematodes (Pratylenchus species) affect over 400 different plants. This nematode causes a lesion disease which, as the name suggests, creates lesions on root surfaces. Lesions are areas of plant tissue that appear dark, from a red-brown to black, where the tissue is dying. In severe infections of lesion nematodes, the entire root system may rot and die, particularly if the plant is already stressed, under attack by another pathogen or in decline. For control of lesion nematode disease, consider preventive and diagnostic options. Before planting, apply a fumigant-like methyl bromide to prevent the occurrence of parasitic nematodes. After planting, make sure weeds are removed from the crop area, as weeds are often host plants to nematodes. Additionally, apply a nematicide such as aldicarb or oxamyl to rid your plants of lesion nematodes, as directed by the American Phytopathological Society.
Sting nematode disease is caused by the pathogen Belonolaimus longicaudatus and other pathogens of the Belonolaimus species. These nematodes attack a number of hosts including trees, grass, vegetables and other crops. Sting nematodes parasitically feed on the tips of roots. Plants may suffer partial destruction of roots that renders the plant incapable of absorbing necessary water, the plant above ground may suffer from overall decline, the plant may experience stunted growth and deformed plant parts and in severe cases, the entire root system may die, according to the American Phytopathological Society. For control, the best option is nematicides and cultural control. For cultural management, make sure you plant clean, uninfected plants; consider adding organic amendments to soil to increase potential for nematode resistance. A chemical option includes nematicide application; use carbamate or organophosphate to decrease sting nematode infestations. Additionally, a biological control method includes the use of Pasteura usgae, a soil-inhabiting bacteria that helps control sting nematode populations.