BP Singh

Symptoms of Nematode Damage 205Abnormal growth and swellings: Nematode infection may causeabnormal growth of stem and leaves as a result of hypertrophy andhyperplasia. Such swellings can often be of diagnostic importance.A. tritici produces swellings near basal part in about 3 week oldseedlings. Swellings in infected tissue are also caused by D. dipsacion narcissus and A. ritzemabosi on strawberry.Below ground symptomsRoot galls : PreSt'net.' of galls on roots is characteristic symptomproduced b\ r\ lIlt-knot nematodes (Meloidogyne spp.), Falserootknot I1L'matode (Nacobbus spp.), and Ditylenchus radicicola.Small root galls are also produced by Hemicycliophcra p.renaria onCitrus and Xiphinema diversicaudatum en roses. The size and formof galls formed varies with the species involved, infection leveLhost species and age of plant. In papaya, root-knot nematodeproduces galls as large as golf balls while in grapE-vine galls arEquite small. Nacobbus sp. produces galls in strands or bead likefashion along the root.Root lesions: Small or large dark necrotic lesiom are producedby migratory endoparasites as. species of lesion nematodePratylenchus, burrowing nematode Radopholus similis and rice roctnematode, Hirschmanniella sp. The lesions IDay ultimately coalasceleading to browning of roots. On large roots, lesions can formcallused margin. Root lef'ions may somtimes be caused l::yectoparasites as Cricone11;.oides sp.Excessive root branching : Nematodes as Mtloidogyne sPF.,Heterodera spp. and Nacobbus spp. can stimulate development ofbranch rootlets near the pOint of invasion leading to excessive rQ(ltbranching variously called as' witche's broom, hairy root andbearding'.Discolouration, necrosis and decortication of re.ots : Nematodefeeding specially by ecto and semiendo parasites result in smallsuperficiG'.1 areas of necrosis which may spread resulting incomplete browning of roots. These sympt.:>ms < re indicative ofinfection by species of Xiphinema, Tylenchullls, Htlicotylenchu5 alldAphelenchoides parietinus. In citrus, feeder ['Dots infected with T.semipenetrans are slightly thicker than healthy on('s and have dirtyappearance due to adhering.of soil particle.::; to gelatinous eggsacsof nE:ma tode. Heavy nematode infection results in cC'rtical ~ ~oughing.