BIOLOGICAL-CONTROL OF PLANT-PARASITIC NEMATODES

Population development and activities of plant-parasitic nematodes in soil are limited by a number of antagonistic organisms. Bacteria and other prokaryotes can parasitize nematodes directly (Pasteuria penetrans) or may kill or inhibit nematodes through production of toxins, metabolites, or enzymes that destroy eggs or other life stages of the animals. Many rhizosphere bacteria are antagonistic to nematodes. Nematode trapping fungi such as species of Arthrobotrys, Catenaria, Oligospora, among others, form mycelial structures with which they can immobilize and destroy nematodes. Other fungi invade the nematode body forming endospores (Myzocytium spp., Haptoglossa spp.), while others (Gliocladium spp., Paecilomyces spp., Verticillium spp.) penetrate and destroy eggs, females, or cysts. Other soil organisms that are antagonistic or predatory of nematodes include microarthropods, nematodes (orders Dorylaimida and Mononchida), and protozoans. Efforts to inoculate soil with microbial species antagonistic to phytonematodes to enhance biological control have not been successful for practical agriculture. The addition of organic amendments to soil can stimulate microbial activities detrimental to plant-parasitic nematodes. Amendments containing chitinous materials and (or) amine N are most effective for controlling nematodes. Organic amendments with high amine N content can be used practically to suppress phytonematodes and provide adequate nutrition to crops. Cropping systems determine the composition and activities of the soil microbiota antagonistic to nematodes. Some cropping systems increase the level of microbial antagonism to nematodes in soil.