PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
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1) Rhizome rot/s<strong>of</strong>t rot – Pythium sp.<br />
DISEASES OF ZINGER<br />
Symptoms<br />
Rhizome rot <strong>of</strong> zinger is common in all zinger growing areas. When infection takes<br />
place through contaminated seed, sprouts fail to grow resulting in pre-emergence<br />
damping <strong>of</strong>f.<br />
If the disease strikes after sprouting it manifests itself on the leaves, which turn<br />
pale green in colour.<br />
Yellowing is noticed on the top leaves, gradually spreading downwards <strong>of</strong> the leaf<br />
blade and leaf sheath along the margin.<br />
Yellowing is followed by withering and drying <strong>of</strong> the dead area gradually<br />
extending to leaf sheath. Dead leaves ultimately drop <strong>of</strong>f and hang down along the<br />
stem till the entire shoot becomes dry.<br />
On stem, a translucent brown lesion develop at collar region and later becomes<br />
water soaked and s<strong>of</strong>t, extends to whole shoots and can be easily pulled out from<br />
this point.<br />
S<strong>of</strong>t rot extends from the collar region to rhizomes which first become discoloured<br />
and gradually decompose, forming a watery mass <strong>of</strong> putrifying tissues enclosed by<br />
tough ring <strong>of</strong> rhizome.<br />
The fibrovascular strands are rarely affected. Roots arising from affected rhizome<br />
undergo rotting and s<strong>of</strong>tening. Rotting is also noticed in rhizomes collected from<br />
infected crop during storage.<br />
Disease cycle<br />
P.I: Survive in soil and infected rhizomes as oospores<br />
S.I: Spreads through irrigation water as zoospores<br />
Favourable conditions<br />
Mimegralla flies play a role in the spread <strong>of</strong> the pathogen<br />
Management<br />
Crop rotation for 3-5 years with non-host crops<br />
Avoid water stagnation<br />
Collect the seed from disease free plots<br />
Rhizome treatment with Metalaxyl@0.2%<br />
Drench the field with COC@0.3% or Metalaxyl@0.2%<br />
Control the Mimegralla insects by 0.05% methyl parathion<br />
2) Leaf spot – Phyllosticta zingiberi<br />
Symptoms<br />
In A.P., the disease is common during monsoon months.<br />
Initially disease appears as small, yellowish oval to elongated spots on the leaves<br />
measuring 0.5 to 1 mm.<br />
The spots enlarge; turn to white and papery at the centre with dark brown margin<br />
surrounded by a yellow halo.<br />
Spots are usually isolated but under humid conditions they coalesce with one<br />
another developing towards margin forming a big lesion<br />
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