Nematodes

Nematodes, or roundworms, are microscopic worm-like organisms. Taxonomically, nematodes belong to the clade Ecdysozoa, which includes arthropods and other moulting animals. They can be found in a very wide range of habitats, and most are innocuous. There are about 4,100 plant-parasitic nematodes, and the vast majority of these are pests in agriculture. Some nematodes are important predators (genera Heterorhabditis and Steinernema) that attack several insects, particularly those inhabiting the soil. This database contains information on two species of plant-parasitic nematodes. Although the pinewood nematode does not cause disease in North American pine species and is not considered a pest in this country, it is a significant pest in other regions of the world, including China, Japan, and Korea and, more recently, Portugal and Spain, where it causes wilt disease and widespread tree mortality.

Order Rhabditida

Family Aphelenchoididae

Most nematodes in this family feed on fungi (mycetophagous). They are found in a diverse array of habitats, from soils to decaying plant material to tree bark, and in the tunnels of wood-boring beetles. A few species can be found in marine habitats. Some species are also parasites or predators. Members of this family are microscopic to small, slender worm-like organisms about 0.2–2.0 millimetres in length. There are more than 300 species in this family. Two genera, Aphelenchoides (>100 species) and Bursaphelenchus (>40 species) cause economically important plant diseases, but a few species in the latter genus cause economically important diseases in trees, often because of their association with bark beetles, longhorn beetles, and weevils, which act as vectors transporting the nematodes to their hosts.

Family Pratylenchidae

This family primarily consists of obligate parasites that target the roots of higher plants. They can be either migratory or sedentary parasites. Genera in this family cause serious diseases in agricultural crops. Adult nematodes are microscopic to small, slender worm-like organisms about 0.3–4 millimetres in length.