The Influence of the Density of Nematode Populations On Plants

Abstract

Pot experiments indicated that top growth in some species of plants was stimulated by low numbers of larvae of Meloidogyne javanica (Treub). In such plants, root weight increased as numbers of nematodes increased. In a second group of plants, weights of tops were not influenced by nematode density and in a third group of plants, weights of tops decreased linearly with increasing nematode numbers, The differences in the responses of plants to infection by M, javanica is considered to be the result of the interaction between inhibitory and stimulatory processes in the plant. Plants in which top growth remains constant up to a particular nematode density, the tolerance level, are considered to be just one example of a series of possible relationships between the stimulatory and inhibitory processes. Studies on the relationship between numbers of Helicotylenchus dthystera (Cobb) and the growth of turf and between Trichodorus porosus (Allen) and the growth of pine seedlings are discussed in relation to the usefulness of the concept of tolerance level in field ecology.