Disease Management

Pepper Root Knot

Root-knot Nematodes of Peppers

Most agricultural soils contain a complex community of nematodes, most of which feed on fungi or bacteria and are important in decomposition and the recycling of nutrients. Nematodes are microscopic roundworms that are abundant in soil, freshwater, and marine habitats. Many species are parasites of animals, insects, or other invertebrates. Plant-parasitic nematodes feed on plant roots by means of a stylet, a needle like mouthparts which is inserted into cells to remove cell contents. Root-knot nematodes (Meloidogyne species) are the most serious nematode parasites of peppers. Different species occur worldwide and have wide-host ranges including most solanaceous crops. The most common species in cool, temperate regions is M. hapla.

Symptoms of root-knot nematode are characteristic of root damage: stunting, wilting, chlorosis, and reduced fruit yield and size. Plants fail to respond to fertilizer applications. Root-knot nematodes enter roots through root hairs and become sedentary (endoparasites). They induce giant cells to form in the root system which are apparent as galls or knots. A female will produce hundreds of eggs in a gelatinous matrix on the surface of the galls. Galls may also be invaded by secondary organisms that cause further root decay. Root-knot nematodes are known to exist as distinct races that vary in host range and pathogenicity.

Management

• Resistant cultivars of chili and sweet pepper are available.
• Start with nematode-free transplants. Discard seedlings with slight galling.
• Successful crop rotation is difficult due to the many species and races of Meloidogyne that may be present. Grass, sorghum, corn, or tropical legumes may be useful for crop rotation.
• Control weed hosts.
• Removal of galled root systems is an important sanitation procedure.
• Soil solarization may reduce populations in the upper layers of the soil.
• Chemical or fumigant nematicides can be used for high value crops.