Extensio n Folder No . 19

THE BURROWING NEMATODE -Radopholus Similis

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CENTRAL PLANTATION CROPS RESEARCH INSTITUTE I'NDIAN COUNCIL OF AGRICULTURAL RESEARCH)

Kasaragod • 670 124, Kerala, India CPCRI

The burrowing Nematode, Radopho/us simi/is

The burrowing nematode. Radopho/us simi/is is the most important nematode pathogen infesting coconut. arecanut. black pepper, banana and betelvine. This nematode is w idely distri­buted in South India and is also reported from Lakshadweep Island. The nematode has a very wide host range covering more than 300 species of plants including trees, shrubs and herbs. Ginger, t urmeric. sweet potato, sugarcane, groundnut, avacado, nutmeg. tea, coffee. cardamom are other important crops known to bE> susceptib le to this nematode.

Burrowing nematode is a notorious pathogen for causing the pepper yellows in Indonesia, spreading decline of citr us in Florida and toppling disease of banana in all banana growing reg ions of the world except in Israel and Taiw an. Parasitization by R. simi/is causes gross reduction in the quality and quantity of yield. In Kerala, the slow w ilt disease of black pepper ca used by R. simi/is is known to cause an annua I loss of 10 per cent vines.

Symptoms of damage:

The burrow ing nematode infested plants exhibit general ye llowing and visible reduction in growth, vigour and yield. These above ground symptoms are non-specific and the only definite metho d to identify an infested plant is to look for symptoms on fresh roots. The nematodes produce small, elongate, orange coloured lesions on the creamy w hite to light orange coloured port ion of the main tender roots of coconut and arecanut, but on tender roots of banana, black pepper, betelvine, avacado and other plants, lesions are brownish to black. These lesions coalesce and cause extensive root-rotting. Tender coconut roots on heavy infestat ion beccme spongy in texture. As high as 4000 nematodes are harboured by one gram (one inch length) of main coconut roots. Lesions and roni ng are more on the tender portions of roots and do not normally occur On the hard, older red or brown coloured portions of roots.

Biology: The nematode takes three weeks to complete its life cycle from egg to adult at a temperature range of 24-32 0 C. All larval stages and females except males are infective. They enter into the tender roots and feed in the cortical region of coconut and areca nut roots. It is a migratory endoparasite causing maximum root damage and is capable of spending its entire li fe in the roots.

Ecology: Nematodes being moisture dependent, their population fluct uations are markedly affected during su mmer months. Maximum nematode populations occur during Septem­ber to November and the minimum during April to June. The nematode is known to survive and increase best in deep, well drained sandy loam soils but less in shallow. poorly drained clayey soils. The cocon ut iso late of R. simi/is w as found to survive in host fl ee dry sandy soil for three months and in host free w et soi l for 15 months under green house conditions. Active nematode populations could be recovered from roots of felled palms for a period of six months.

Dissemination: Nematode is disseminated mainly through t he infested planting materials, floods, irrigation water, farm implements and bulk transport of soil.

Control: Cultural operations, field sanitations, organic amendments, resistant varieties, appl ication of nematicides are the important components in preventing crop loss due to nematode infestation.

1. Spread of nematodes can easily be prevented through the supply of nematode free planting materials. In the case of coconut and arecanut seeds may be supplied instead of seedlings. Seedlings of coconut and arecanut and cunings of black pepper may be raised in polybags containing soil fumigated w ith Methyl bromide and certified free of nematodes before release to farmers.

he burrowing Nematode, Rsdopho/us similis

he burrowing nematode, Radopho/us simi/is is the most :lOt nematode pathogen infesting coconut. arecanut, black , banana and betelvine. This nematode is w idely distri­in So uth India and is also reported from Lakshadweep

The nematode has a very w ide host range covering ~ han 300 species of plants including trees. shrubs and

Ginger, t urmeri c. sweet potato. sugarcane, groundnut, 10, nutmeg, tea. coffee. cardamom are other important <nown to b& susceptible to this nematode.

urrowing nematode is a notorious pathogen for causing pper yellow s in Indonesia, spreading decline of citrus in

and toppling disease of banana in all banana growing I of t he world except in Israel and Taiw an. Parasiti zation :imiJis cau ses gross red uction in the quality and quantity d. In Kera la, the slow wilt disease of black pepper I by R. similis is known to ca use an ann ua I loss of 10 1t vines.

toms of damage:

1e burrowing nemat ode infested plants exhibit genera l ing and visible reduction in growth, v igour and yield. above ground symptoms are non-specifi c and the only l method to identify an infested plant is to look for )ms on fresh roots. The nematodes produce small, elongate. ! coloured leSions on the creamy white to light orange ld portion of the main tender roots of coconut and ut, but on ten der roots of banana. black pepper, betelvine, '0 and other pla nts, lesions are brownish to black. These

coalesce and cause extensive root- rotting. Tender .t roots on heavy infestation become spongy in texture. h as 4000 nematodes are harboured by one gram (one mgth) of main coconut roots. Lesions and rotting are In the tender portions of roots and do not normally occur hard, older red or brown coloured portions of roots.

Biology: The nematode takes three weeks to complete its life cycle from egg to adult at a temperature range of 24-32 0 C. All larval stages and females except ma les are infect ive. They enter into the tender roots and feed in the cortical region of coconut and arecanut roots. It is a migratory endoparasite causing maximum root damage and is capable of spending its entire life in the roots.

Ecology: Nematodes being moisture dependent, their population f luctuations are markedly affected during su mmer months. M aximum nematode populations occur during Septem­ber to November and the minimum during April to June. The nematode is known to survive and increase best in deep. well drained sandy loa m soils but less in shallow, poorly dra ined clayey soils. The coconut isolate of R. simi/is was found to su rvive in host fi ee dry sandy soil for three months and in host free wet soil for 15 months unde r green house conditions. Active nematode populations could be recovered from roots of fe lled palms for a period of six months.

Dissemination: Nematode is disseminated mainly through the infested planting materia ls, floods, irrigation water, farm implements and bulk transport of soil.

Control: Cu ltural operations, field san itations, organic amendments. resistant varieties, applicat ion of nemati cides are the important components in prev~nting crop loss due to nematode infestation.

1. Spread of nematodes can easily be prevented through the supply of nematode free planting materials. In the case of coconut and arecanut seeds may be supplied instead of seedlings. Seedlings of coconut and arecanut and cuttings of black pepper may be raised in polybags containing soil fumigated with Methyl bromide and certified free of nematodes before release to farmers.

2. Sanitation methods such as bUf"lng of planting pits,

avoiding running water f rom infested fields to uninfested fields,

removing soil from agricultural implements w hile transporting

from a nematode infested fields to non-infested field are helpful

in preventing spread of the nematodes.

3. Organic amendments of soil help in suppressing

nematode populaticns and increasing the yield. Application of

neem oil cake to yellow leaf disease affected arecanut pa lms

@ 1.5 Kg/palm, applied in June, September and January is

known to reduce the disease indices, nematode populations and

increase the yield. Si mi larly 30 per cent increase in yield and

5 to 10 per cent decrease in disease indices of coconut palms

affected with root (wilt) disease occurred w ith the application of

Marotti cake (Hydnocarpus) @ 4 Kg/palm in J une an d October.

4 . Application of phorate @ 10 9 a.i/palm to coconut

and @3 9 a.i. to arecanut, black pepper and ba na na in M ay-June

and September-October is known to reduce nematode popula ­

tions and increase yield Significantly.

5. Effective control of R. simi/is in cocon ut nursery is

possible with t he application of phorate @ 2.5 g/ seedling

during September, December and May.

6. Nematici des have to be applied on or very near to the

root system by removing the top soil w ithout causing damage

to the root system in the basin and covering it back w ith the

sa me soil immediately. In the absence of sufficient soil moisture

at the ti me of application of nematicides, the crop should be

irrigated. The t reatment has to be continued for 3-4 years for

achieving a satisfactory control of R. similis population in a

severely affected perennial cropping systems.

7. One of the mos t economica l and effective ways of

tontrolling nematodes is by growing nematode res istant plant

cultivars. In view of its importance, most of the available

coconut and arecanut germplasm collections have been screened

against R. simi/is. The results indicated that coconut hybrids,

West Coast Tall x Gangabondam and Chandra Sankara

(COD x WCT), and arecanut cultivars Hirehalli, Sumangala

(VTL-11), and Sreemangala (VTL-17) are tolerant to the burrow ­

ing nematode. These varieties are recommended for planting

in nematode infested areas.

*

Co ver: Nematode damaged roots, Inset : adu lt ne matode

Published by M . K. Nair Director, CPCR I, Kasaragod-670 124 Kerala

Material prepared and Edited by : P. Sundararaju

and P. K. Kosh-y Jan.- -1990

Printed at Sharada Press, Mangalore.