Studies on the relationship between the density of Meloidogyne exigua population and the mortality of rubber trees

The wide distribution and dissemination of Meloidogyne exigua in rubber tree plantations (Hevea brasiliensis), together with its high reproductive capacity and aggressiveness, make this nematode a limiting factor for the development of rubber tree cultivation. This study evaluated the population density and spatial pattern of M. exigua race 3 and its relationship to the growth and survival of rubber trees in the Triângulo Mineiro—Minas Gerais. The study was done in an area planted in Jan/2008, with the clone RRIM600, and 7.2 hectares were sampled. The population density of the nematode was estimated, as well as the distribution of plant mortality using the Spatial Analysis based on Distance indices—SADIE method, calculating the basal area and constructing maps representing the variations in M. exigua population and rubber tree mortality. The spatial distribution of the nematode population in the soil and roots revealed the presence of three clusters, with a concentration of nematodes above 5.800 individuals per 150 cm³ of soil and 50 g of roots. The incidence of dead trees ranged from 0 to 70%, with two foci of high mortality. The greatest population density of M. exigua in the area studied was concentrated in the clusters, coinciding with the greatest number of dead plants in the direction of the planting lines. Nematode spatial distribution was aggregated, according to SADIE, M. exigua  affectd the growth and survival of rubber trees, reducing the development of trees in the productive phase.