Cotton

Diseases

Cotton Leaf Curl Virus

Cause:

The disease causing virus belongs to Gemini group.
Symptoms: Upward and downward curling of leaves accompanied by small as well as main vein thickenings (SVT as well as MVT) on leaves, pronounced on underside. If a diseased leaf is viewed from beneath against the light, thickened vein found darker green and opaque than the normal. In extreme but not in frequent cases, formation of the cup shaped or leaf laminar (veins) out growth called “enation” appears on the back or underside of the leaf. The newly produced leaves are small, excessively crinkled and curled at the edge. The primary stem often tends to grow taller than normal. The enter-nodes being elongated and irregularly curved but sometimes the whole plant is stunted. The flowers checked in growth and become abortive. Bolls remained small in size and failed to open. All parts of badly hit plants are very brittle and ready broken.

Transmission:

The disease transmitted by feeding of the white fly, Bemisia tabaci within 6.5 hours. A single female, carrying virus can infest many plants. It may also be kept in mind that white fly is known to survive on as many as 53 host plant species, and is responsible for transmitting 23 crop diseases in region. At global level, white fly infests 600 different plant species.

Root Rot

Cause: The fungi Macrophomina phaseoli, Rhizoctonia spp., Fusarium spp. etc. are predominantly isolated from diseased roots.

Symptoms: The disease affects the roots exclusively, causing pre-wilt shedding of leaves, yellowing of foliage, disintegration of root tips, discoloration and shredding of roots, exudation of drops of smelly liquid from the rotted plant parts. Mostly, wilting of shoots occur in only few diseased plants, which ultimately results in the death of entire plant. This disease generally appears, when plants are about 4-6 weeks old and continue up to boll formation. Diseased plants can be easily pulled out of the soil, appears in patches. Roots and root-lets show rotting, yellowing, disintegration and shredding.

Perpetuation: Disease causing fungi are soil borne, hence it may be claimed that both (fungi and soil) factors are responsible.

PICKING/ HARVESTING

Cotton bolls in the same fields open at different times. There is a gap of at least 2 months before first and last boll opens. Thus picking should also be done in accordance, at least 2-3 pickings are required to completely harvest the crop. Picking of cotton usually start in September and continues till December or even January. Picking can be both manual and mechanized. The lint from the first and last pickings should be kept separate because the fiber from the last picking is of comparatively low quality w.r.t first one or two pickings.

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