PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
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LECTURE 11<br />
DISEASES OF CRUCIFERS<br />
1) Club root <strong>of</strong> crucifers or Finger and toe disease: Plasmodiophora brassicae<br />
Fairly severe in hilly regions on cabbage, cauliflower and other crucifers. Fields once<br />
infested with the club root pathogen remain so indefinitely and become unfit for<br />
cultivation <strong>of</strong> crucifers.<br />
Symptoms<br />
Infected plants have pale green to yellowish leaves initially. Later, infected plants<br />
show wilting in the middle <strong>of</strong> hot, sunny days, recovering during the night<br />
Stunting <strong>of</strong> above ground parts and reduction in size <strong>of</strong> heads<br />
Characteristic symptoms become apparent in advanced stage <strong>of</strong> root infection as<br />
spindlelike, spherical, knobby, or club-shaped swellings.<br />
The swellings may be few, or they coalesce and cover the entire root system<br />
Disease cycle<br />
P.I: Soil borne resting spores, which survive for longer periods in soil (10yrs.)<br />
Collateral hosts: Broccoli, Brussels sprout, cabbage, cauliflower, Chinese cabbage,<br />
mustard, raddish, turnip<br />
S.I: Resting spores or zoospores carried through irrigation water or by root contact<br />
Favourable conditions<br />
It occur at a temp range <strong>of</strong> 12-27 0 C (25 0 C)<br />
High soil moisture<br />
Neutral to acidic soils 5-7.0 pH<br />
Management<br />
Use <strong>of</strong> seedlings from disease free fields<br />
Plant cabbage and other susceptible cruciferous crops in well drained fields that<br />
have a pH slightly above neutral (usually about pH 7.2)<br />
Crop rotation does not work since pathogen persists long in soil.<br />
Add hydrated lime to soil to increase pH to 7.2 ( 6weeks before planting @<br />
2.5T/ha)<br />
Avoid excess irrigation<br />
Treat the soil <strong>of</strong> seed bed areas with chloropicrin, methyl bromide or vapam two<br />
weeks before planting. Drenching soil with a solution <strong>of</strong> Brassicol<br />
(Pentachloronitrobenzene)<br />
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