II. GRAPEVINE
Grapes are one of the cosmopolitan crops of agriculture, providing fruit, resin and wine to most of the world. There are many nematode species that attack grapes. The major ones are root knot nematode (Meloidogyne spp.), root lesion nematode (Pratylenchus spp.) and Xiphinema spp. The nematodes of minor importance are the reniform nematode (Rotylenchulus reniformis), the citrus nematode (Tylenchulus semipenetrans) and Paratrichodorus minor. All these nematode species reduce the effective root system through killing of many feeder roots.
a. Root-knot nematode (Meloidogyne spp.)
Of the six species of root-knot nematode reported on grapes in various parts of the world, M. incognita, M. javanica, M. arenaria and M. hapla, are most widely distributed.
Distribution
In India M. incognita and M. javanica are prevalent in grape cultivating regions of Tamil Nadu, Karnataka, A.P., Haryana, Punjab and Maharashtra.
Nature of Damage:
- Endoparasitic sedentary mode of parasitism.
- The freshly hatched second stage juveniles penetrate through young feeder roots, form giant cells around nematode head and feed upon the cell sap thus devitalizing the cells.
- As a result of nematode feeding, numerous fine rootlets are formed at the infection site, thus leading to a ‘hairy root’ condition.
Symptoms:
- Patches of stunted vines with poor branching and scanty foliage
- Lowered yields
- Increased sensitivity to other micro-organisms.
- Distinctive root symptoms with small swellings or galls on feeders and young secondary rootlets.
- These symptoms are worse in sandy soil.
b. Root Lesion Nematode (Pratylenchus spp.)
Distribution
The nematode exists in almost every grape producing region. Different species of this nematode prevail in grapes in different parts of the globe. The most prevalent are P. vulnus, P. scribneri, P. brachyurus and P. minyus. Pratylenchus coimbatorensis has been reported from South India.
- All the stages of these migratory endoparasitic forms are infective. The nematodes remain confined to cortical tissue.
- Affected plants exhibit non specific symptoms like poor growth and low yields.
- Young vines if infected, are unable to develop a root system and ultimately die.
- The roots system of matured vines is badly affected giving rise to a matted, witch’s broom effect in some parts of the root system.
c. Dagger nematode (Xiphinema spp.)
Distribution
This nematode is a pest of grape vine world wide. Though number of Xiphinema spp. have been found from grape vines, only two viz., X. index and X. americanum are found to be of pathogenic significance. While X. index has been reported from Europe, South Africa, Victoria, USA, North Africa, Iraq and South America, X. americanum has been recorded from Indian vineyards.
- The nematode is highly damaging to grapevine seedlings where it feeds as a migratory ectoparasite.
- X. index causes characteristic ‘Curly tip’ symptom on grape seedlings.
- Infested roots are necrotic, lack laterals, have root tip swellings, show cellular hypertrophy and multinucleate cells near nematode feeding site. This results in reduced root system.
Management:
- Certified, nematode free rootings should be grown for new vineyards or replants.
- Intercropping of marigold (Tagetes patula) reduces nematode population and improves the yields significantly.
- Old root system should be removed.
- Use of resistant root stocks viz., 1613, Dogridge, Saltcreek, Harmony (1613 x Dogridge), Lake Emrald, Tompa etc. is beneficial against nematode.
- Soil application of carbofuran or phorate at 6 kg a.i. /ha is effective against the nematodes and results in the increased fruit yield.
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