PATH 372 Diseases of Horticultural Crops

Minute yellow spots surrounded by a grayish margin appear on leaflets. Gradually,
the centre of the spots turns grayish white with dark brown margins and a yellow
halo.
Spots coalesce into irregular necrotic patches
Complete drying and shrivelling of leaf blade occur giving a blighted or burnt
appearance.
Large number of globose or ovoid black acervuli appears on the upper surface of
affected leaves.
Pathogen
The fungus produces conidia inside the acervuli. The acervuli are black in colour,
cushion shaped, sub-epidermal and break open to expose conidia and black sterile
structures, setae. The conidiophores are hyaline, short and simple, bear conidia at the
tip singly. The conidia are five celled, the middle three cells are dark coloured, while
the end cells are hyaline with 3-5 slender, elongated appendages at the apex of the
spore.
Disease cycle
P.I: Conidia in plant debris
S.I: Conidia carried by wind splashed rain water
Management
Remove older affected leaves and burn
Apply heavy disease of potash and improve drainage condition of soil
Spray foliage with BM@1% COC or captan @0.2%
1) Bunch rot: Marasmius palmivora
DISEASES OF OILPALM
Symptoms:
Strands of mycelium are seen spreading over the bunch surface in initial stages
Mycelium is profuse at the back of the bunch.
Mycelium grows over the fruit surface and penetrates the mesocarp and leads to
wet rot.
Disease spreads rapidly within 2 to 3 months after initiation of monsoon rains.
Management:
Crown cleaning by removing aborted and dried bunches and inflorescences.
Spraying of Carbendazim 0.1% or Bordeaux mixture 1%.
2) Spear rot: Phytoplasma disease
Spear rot is an endemic disease in Kerala state.
Symptoms:
Disease is characterized by chlorosis of young whorl of leaves followed by
necrosis.
Rotting of spear leaves
Reduction is leaf size
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