Etiology of the yellowing and wilt diseases of black pepper (Piper Nigrum L.)

Date

10-1990

Abstract

The cause of the yellowing and wilt diseases attacking black pepper (Piper nigrum L.) observed in the Bicol Region was investigated and determined as Meloidogyne incognita Chitwood. Initial symptom was slight to general yellowing of leaves. Wilting occurred two to three months later after heavy, continuous rains followed by sunny, warm and dry weather. The nature of the symptoms was similar to those caused by a wide range of biotic and abiotic factors.

A survey for the presence of Meloidogyne incognita in black pepper plantsfrom 4 provinces, 12 towns and 14 barangays in the Bicol Region showed 64.3% of the 70 samples had galls. Personal assessment of loss in stand was 10 to 65%. Suspect fungal pathogens were ruled out, particularly Phytophthora spp.despite a rapid isolation technique using pimaricin-vancomycin-pentachloronitro-benzene-hyymexazol (PVPH) selective medium.

Identification of the nematode species was by the characteristic perineal patterns of the adult female nematodes. Inoculation tests on black pepper seedlings produced galls using different levels of egg mass and larval inocula. Differences between root and shoot weights in inoculated and uninoculated plants were not statistically significant at 5% level. Yellowing and witling symptoms accompanied by severe root decay and rotting occurred six months after inoculation.

Root-knot nematodes of different developmental groups were recovered at weekly periods after inoculation. One complete life cycle occurred between 21 to 28 days after larval inoculation.

The histopathology of the black pepper nematode revealed the formation of gian cells and galls, distorting the cortical cells and disrupting and blocking the vascular bundles. Multiple infection in the roots produced more galls and giant cells, thus more damage to the plant.

The host range of the nematode included the common intercrops Ipomoea batatas L., Solanum melongena L., Vigna unguiculata L. and Phaseolus vulgaris L., The weed species, Paspalum conjugatum Berg., Ageratum conyzoides L., Emilia oleracea L. found near black pepper plnts in the field were also hosts to the nematode, Coffea sp., Theobroma cacao L., Laucaena glauca Benth. And Gliricidia sepium L. were not infected.

Chicken dung at 3.5 tons per ha and carofuran at 2 kg ai per ha gave comparable control of the nematode, while azolla at 2 tons per ha was ineffective.

Document Type

Dissertation

Degree

Master of Science in Plant Pathology

Major Course

Major in Plant Pathology

College

Graduate School (GS)

Adviser/Committee Chair

Delfin B. Lapis

Co-adviser

Tricita H. Quimio, Manolo B. Castillo

Committee Member

Restituta P. Robles, Lina L. Ilag

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 996 1990 P57 Z37

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