Plant Diseases Caused by Nematodes
Namikoye, Everlyne Samita
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Nematodes are lower invertebrate animals and are perhaps the most numerous multicellular animals on the earth. They are generally free-living in marine, freshwater or soil environments, but a large number of species are parasitic to different kinds of plants and animals. The parasitic species are of considerable agricultural, clinical and veterinary importance as pests of plants and parasites of man and livestock respectively. Plant parasitic nematodes (PPN) are eel worms which are essentially aquatic and spend a greater part of their life cycle in the soil. They feed on the surface or the peripheral layers of the root or enter the root and feed from within with the help of a feeding structure called the stylet. Infected plants in general exhibit stunting, yellowing of leaves, wilting and reduced yield, in addition to several below-ground symptoms. Plant parasitic nematodes lay eggs singly or in masses either in the soil or within plant tissues. Most PPN have four larval stages between the egg and adult, with intervening moults. A life cycle from egg to egg can be completed within 3-4 weeks under optimum environmental conditions; temperature being the key factor in determining the duration of the life cycle. This topic deals with how nematodes cause diseases in plants, the symptoms they induce, their lifecycle an interaction with other disease causing agents, their life cycle, dispersal and survival. The above components are discussed in relationship to the control and management of diseases.