PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
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2) Downy Mildew – Peronospora parasitica<br />
Severe in raddish, cabbage, cauliflower, mustard, and knol-khol.<br />
Symptoms<br />
Small purplish brown spots on under surface <strong>of</strong> leaves<br />
Small, pale yellow angular spots on upper surface <strong>of</strong> leaves, with downy growth on<br />
the under surface.<br />
The spots coalesce and the leaves shrivel and dries up prematurely<br />
In cabbage, these spots expose the heads to s<strong>of</strong>t rot<br />
Cauliflower curds look brownish at the top<br />
Stems show dark brown and depressed lesions or streaks which later develop<br />
downy growth <strong>of</strong> fungus<br />
Disease cycle<br />
P.I: Oospores in infected plant parts or in soil<br />
S.I: Wind borne sporangia<br />
Management<br />
Destruction <strong>of</strong> infected plant debris<br />
Avoidance <strong>of</strong> thick sowing and excessive moist conditions<br />
Spray metalaxyl@0.25% or COC@ 0.3% or Mancozeb@ 0.2% at 10 days interval<br />
3) Powdery mildew – Erysiphe polygoni<br />
Symptoms<br />
Seen on cabbage & cauliflower<br />
Symptoms<br />
White powdery spots on the upper surface <strong>of</strong> leaves, stems, flower parts etc.<br />
Finally the mildew may cover the entire surface.<br />
Disease cycle<br />
P.I: Mycelium in infected plant debris<br />
S.I: Wind borne conidia.<br />
Management: Application <strong>of</strong> Dinocap@0.2%<br />
4) Alternaria leaf spot: Alternaria brassicola, A.brassicae, A.raphani<br />
Common on cabbage, cauliflower and mustard.<br />
Symptoms<br />
Spots are small, dark coloured<br />
They enlarge, soon become circular & 1mm. in diameter<br />
Under humid conditions groups <strong>of</strong> conidiophores will be formed in the spot<br />
Spots develop concentric rings<br />
Finally the spots coalesce leading to blighting <strong>of</strong> leaves.<br />
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