Importance of Plant Parasitic Nematodes in Colorado Crops

Nematodes are worm-shaped nearly microscopic animals, many of which are virtually invisible to the unaided eye when they are in the soil or within plant material. Of the known nematode species, approximately 50%, 25%, 15%, and 10% are free-living, marine, animal parasites, and plant parasitic nematodes (PPNs), respectively. Freeliving nematodes are very important in maintaining the soil bio-dynamic system, especially in soil with low organic matter content, whereas PPNs feed on plants and reduce crop growth and yield efficiency. Free-living nematodes help in microbial colonization of substrates and mineralization of nutrients by disseminating microbial propagules throughout soil. In addition, nematode metabolites may also stimulate specific bacterial growth by releasing growth-limiting nutrients such as nitrogen (N) and vitamins. Many feed on bacteria and fungi within the soil and are, in turn, preyed upon by generalist predators (including the omnivorous and predatory nematodes). This improves nutrient cycling and allows slow release of nutrients. The contribution made by free-living nematodes to N mineralization (making N available to plants) and mineralization of other soil nutrients is relatively high compared to bacteria in soil ecosystems. These free-living nematodes also feed on other soil microbes including plant pathogens (bacteria, fungi, and nematodes). Free-living nematodes are important for Colorado soils for any crop production system. Another group, called Entomopathogenic nematodes (e.g., the genera Steinernema and Heterorhabditis), is extraordinarily lethal to many important soil insect pests and yet safe for plants and animals; they are used to control many soil inhabiting insects. Quick Facts