BP Singh

Detection Techniques for Plant Parasitic Nematodes 209mechanical injury, they predispose the plant to other pathogenslike fungi and bacteria. Some plant parasitic nematodes are knownto transmit plant viruses of economic importance.Length of survival in nematodesMost plant parasitic nematodes are subjected to unfavourableconditions sometime duril1g their life cycle and the persistence ofa species in a habitat confirms that the survival mechanisms areoperative. The periods of survival for some economically importantnematode species are given in Table-l.Table 1.Length of survival in some nematodes of quarantineimportanceNematode species Length of Survival conditionssurvivalAnguina tritici 32 years In galls at SoCAnguina agrostis 4 years In galls at room temp.Bursaphelenc1lUs xylophilus 1 year In wood logsDitylel1chus dipsaci 23 years Plant tissue at room temp.Ditylenchus destructor 5 months Peanut hulls at 10 DCGlobodera rostochiensis 2.5 years In cysts at room temp.Heterodera avenae 5.5 years In cysts at SoC & 75% RHHeterodera glycines 6 years Cysts in dry soil at °-20 °CHeterodera schachtii 3 months Encysted eggs in soil at 62°CPratylenchus penetrans 11 months In dry soil in greenhouseRadopholus similis 6 months Without host in field soilIt is clear from Table 1 that certain nematode species havegreater or lesser survival capacity than others. In other wordslength of survival depends on factors like temperature, aeration,moisture, rate of water loss, stage of life cycle and amount of fatsand carbohydrates in nematode body. If the nematodes are notkilled in plant material or seed, activity usually resumes rapidlyupon return of favourable environment.Means of nematode spreadPlant parasitic nematodes move relatively short distancesunder their own power. In a sandy soil under optimum moistureand temperature conditions, a nematode will travel about 30 cm/year. Being very minute in size (average body length 0.5 mmi body