Possibilities for biological control of root-knot nematodes by natural predators in Florida soils

Abstract

Root-knot nematodes (Meloidogyne spp.) are important pests of many landscape and commercial ornamentals grown in Florida. However, soils may contain naturally-occurring predators that may provide some biological control of nematodes. A greenhouse experiment was conducted to evaluate the potential of invertebrate predators in agricultural and natural soils to suppress M. incognita (Kofoid & White) Chitwood on coleus (Coleus blumei Benth.). Soil from adjacent natural and agricultural habitats was collected from three locations in Florida (Quincy, Homestead, and Citra). Each soil was placed into pots, planted with coleus seedlings, inoculated with 2000 eggs of M. incognita, and arranged in a 3 × 2 factorial design. Root-knot nematodes were suppressed in natural soils compared to agricultural soils by the end of the experiment. A variety of invertebrates were monitored in all soils including tardigrades, Collembola, mites, japygids, and ants. Omnivorous and predatory nematodes and enchytraeid worms did not show population patterns consistent with the biological suppression of root-knot nematodes observed in natural soils. However, Collembola and mites were generally more abundant in natural than in agricultural soils, and increased in numbers over time. Japygids, ants, and tardigrades were also more abundant in all or some natural soils initially, but numbers declined over time. Results support the ideas that nematode suppression occurs in Florida soils, that relative suppression of root-knot nematodes is greater in natural than in agricultural soil, and that the occurrence of some invertebrate predators, especially mites and Collembola, is consistent with the nematode population declines observed.