Causal Agent: 

Root-knot nematodes (Meloidogyne incognita)

Characteristic Symptoms:
Infected plants appear chlorotic, stunted, necrotic or wilted especially during periods of moisture stress and high temperatures.
Galls or knots are formed on the roots measuring 1-10mm in diameter or larger depending on the nematode species and gall location in the root system.
Severely infected root system are malformed with shortened and thickened individual roots suppressing root branching and growth. 
Intensive galling reduces root efficiency resulting in permanent wilting, premature defoliation  and plant death.
Conditions for Disease Development:
J2s which are the infective stage of the root-knot nematode are most active at soil moisture levels of 40-60% of field capacity.
They are most abundant causing serious problems to their hosts in sandy soil with good drainage.
Plants stressed physically or by biological factors are more susceptible to attack and damage of nematodes.
Management and Control:
Use resistant varieties, if available.
Crop rotation with non-hosts crops.
Grow crops that are antagonistic to nematodes like marigold to reduce population of plant parasitic nematodes.

Long fallow periods, deep plowing, solarisation are also effective in reducing nematode population.

Use of nematicides like fenamiphos, carbofuran, oxamyl and aldicarb.

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