(Meloidogyne halpa, formerly Meloidogyne marioni), a parasitic worm of the family Tylenchidae, class Nematoda.
The root-knot nematode parasitizes on the roots of plants, causing the formation of round galls. Body length is 1.5-2 mm. The females are milk-white with bloated bodies; the males, with elongated bodies, are rarely found. Living inside the gall, the female lays about 2,000 eggs in a mucous egg sack. Microscopic larvae emerge from the eggs and infect the roots of neighboring plants or form their own galls alongside the mother’s; in this way large (to 2-3 cm) and complex galls develop. The root-knot nematode parasitizes predominantly in southern areas on the most varied hothouse, garden, melon, fruit-and-berry-bearing, and industrial crops. When it reproduces on a large scale the root-knot nematode causes gall nematodiasis in plants and frequently diminishes the harvest of a major crop (for example, cucumbers) by 40-60 percent. To combat root-knot nematodes either antinematode chemical preparations (nematocides) are used or the affected vegetable, melon, or other crop is excluded from crop rotation for two to three years.