PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
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Minute yellow spots surrounded by a grayish margin appear on leaflets. Gradually,<br />
the centre <strong>of</strong> the spots turns grayish white with dark brown margins and a yellow<br />
halo.<br />
Spots coalesce into irregular necrotic patches<br />
Complete drying and shrivelling <strong>of</strong> leaf blade occur giving a blighted or burnt<br />
appearance.<br />
Large number <strong>of</strong> globose or ovoid black acervuli appears on the upper surface <strong>of</strong><br />
affected leaves.<br />
Pathogen<br />
The fungus produces conidia inside the acervuli. The acervuli are black in colour,<br />
cushion shaped, sub-epidermal and break open to expose conidia and black sterile<br />
structures, setae. The conidiophores are hyaline, short and simple, bear conidia at the<br />
tip singly. The conidia are five celled, the middle three cells are dark coloured, while<br />
the end cells are hyaline with 3-5 slender, elongated appendages at the apex <strong>of</strong> the<br />
spore.<br />
Disease cycle<br />
P.I: Conidia in plant debris<br />
S.I: Conidia carried by wind splashed rain water<br />
Management<br />
Remove older affected leaves and burn<br />
Apply heavy disease <strong>of</strong> potash and improve drainage condition <strong>of</strong> soil<br />
Spray foliage with BM@1% COC or captan @0.2%<br />
1) Bunch rot: Marasmius palmivora<br />
DISEASES OF OILPALM<br />
Symptoms:<br />
Strands <strong>of</strong> mycelium are seen spreading over the bunch surface in initial stages<br />
Mycelium is pr<strong>of</strong>use at the back <strong>of</strong> the bunch.<br />
Mycelium grows over the fruit surface and penetrates the mesocarp and leads to<br />
wet rot.<br />
Disease spreads rapidly within 2 to 3 months after initiation <strong>of</strong> monsoon rains.<br />
Management:<br />
Crown cleaning by removing aborted and dried bunches and inflorescences.<br />
Spraying <strong>of</strong> Carbendazim 0.1% or Bordeaux mixture 1%.<br />
2) Spear rot: Phytoplasma disease<br />
Spear rot is an endemic disease in Kerala state.<br />
Symptoms:<br />
Disease is characterized by chlorosis <strong>of</strong> young whorl <strong>of</strong> leaves followed by<br />
necrosis.<br />
Rotting <strong>of</strong> spear leaves<br />
Reduction is leaf size<br />
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