Root - lesion nematodes

Nematodes are tiny but complex unsegmented roundworms that are anatomically differentiated for feeding, digestion, locomotion, and reproduction. These small animals occur worldwide in all environments. Most species are beneficial to agriculture. They make important contributions to organic matter decomposition and to the food chain. Some species, however, are parasitic to plants or animals. Plant-parasitic nematodes in the genus Pratylenchus are commonly called either root-lesion nematodes or lesion nematodes. These parasites can be seen only with the aid of a microscope. They are transparent, eel-shaped, and about 1/64 inch (0.5 mm) long. They puncture root cells and damage underground plant tissues, which reduces plant vigor, causes lesions, and predisposes plants to infection by root-infecting fungi. Root-lesion nematodes obtain sustenance only from living root tissues but may survive from crop to crop in dead root debris and in soil. They are capable of multiplying in a wide range of monocot and dicot host species. Plant-parasitic nematodes are difficult to identify, to control, and to demonstrate as the cause of important crop damage. Root-lesion nematodes have been detected in approximately 90 percent of fields sampled in Idaho, Montana, Oregon, and Washington. Potentially damaging high population densities have been detected in as great as 60 percent of fields sampled in some regions. A particular challenge with root-lesion nematodes is that the symptoms on small grain cereals are non-specific and are easily confused with other ailments such as nitrogen deficiency, low water availability, and the root rots caused by fungi such as Pythium, Rhizoctonia, and Fusarium. Farmers, pest management advisors, and scientists routinely underestimate or fail to recognize the impact of root-lesion nematodes on wheat. It is now estimated that these root parasites reduce annual statewide wheat yields by about 5 percent in each of the Pacific Northwest (PNW) states of Idaho, Oregon and Washington. This generally unrecognized pest therefore reduces annual wheat profitability by about $51 million in the PNW.