Introduction  Anthracnose  Blackarm  Grey Mildew Leaf Curl  Leaf Spots  Little Leaf  Root Rot  Verticillum Wilt  Wilt 
Introduction
The cotton crop sufffers from a number of diseases which can conveniently be classified into foliar and soil borne diseases. The important foliar diseases are bacterial blight caused by Xanthomonas axonopodis Cv.Malvacearnum, leaf spots, caused by Alternaria macropora, Myrothecium roridum and Helminthosporium speciforum. Gray mildew, a foliar disease caused by Ramularia areola which was initially restricted to G.arboreum, is also affecting G.hirsutum. Leaf curl is another devastating foliar disease.
The soil borne diseases include root rots caused by Rhizoctonia solani and R.batalicolaand wilts caused by Fusarium oxysporum and Verticillium dahliae. Root rot and wide spread in the north zone, Fusarium wilt in the black soils of Gujarat, Madhya Pradesh, Maharashtra, Karnataka and Gujarat and Verticillium wilt in Tamil Nadu.
Disease Management Strategies
Bacterial blight and fungal leaf spotSpray the crop using stretocyclin (0.01%) and copper oxychloride (0.25%)Grey mildewSpray wettable S (0.2%) or carbendazim (0.1%)Boll rotSpray copper oxychloride (0.25%) or carbendazim (0.1%) along with the recommended insecticide.Root rotTreat seed with carbendazim 2.3 g/kg seed before sowing. Drench the plants in the affected patch with carbendazim (0.1%). Intercropping with moth bean and application of ZnSO4 kg/ha should be recommended where the disease is prevalent. Seed treatment with antagonists like Trichoderma viride and T.harianum.
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Anthracnose : Colletotrichum gossypii and C. capsici
Mode of survival and spread
Primary inoculum seed-borne ; sec. Spready by soil borne and air borne conidia; survival on collateral hosts.

First seedlings attacked when reddish circular spots on cotyledons and primary leaves; when lesions on collar region the stem is girdled and seedlings wilt and die; boll spotting most common and serious; circular, slightly sunken, reddish brown lesions, deep seated, discoloring the lint to yellow/brown, causing it to rot; fibre brittle.
Control
Seed treatment with organo -mercurials; removal of collateral weed hosts ; spraying plants 2 times with copper fungicides before boll formation.
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Black arm/ angular leaf spot/bacterial blight : Xanthomonas malvacearum
Mode of survival and spread
Primary infection seed borne on the surface; on voluntary plants; sec. spread through wind, water and other physical and biological agents; also on several collateral hosts.
Symptoms

All above ground parts are attacked; on seedlings water soaked lesions on cotyledon which cause distortion and withering of cotyledons and death of seedlings ; water soaked lesions on leaves of mature plants bound by veinlets and turn dark brown to black; on stem brown to black linear sunken lesions which guide the stem; on bolls also sunken spots which are dark brown to black, deepseated and damage the lint fibre and seed.
Control
Acid delinted with conc. Sulphuric acid or organo- mercurials ; internal infection checked by soaking seeds in 100 ppm streptomycin sulphate overnight; secondary spread in field checked by spraying 500 ppm of streptomycin sulphate at 3 week interval ; use resistant varities when available.
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Grey mildew or areolate mildew : Ramularia areola
Mode of survival and spread
Spread by airborne conidia ; survival method not known.

Irregular to angular pale translucent spots usually restricted by veins appear usually on the lower surface of older leaves; in severe infections, leaves turn yellowish brown and fall off prematurely.
Control
Spraying twice with 1% copper fungicide or dusting twice with sulphur.
Leaf curl
The plant disease is now threatening cotton cultivation in north zone. Leaf curl was first noticed in Nigeria in 1912. It is causing considerable damage in cotton fields in north India since, 1993.
The disease is caused by 'Gemini virus' which is transmitted by Whitefly (Bemecia tabaci). The initial symptoms begin on the top newly emerging leaves with the darkening and thickening of leaves. As rains get thickened the leaves either cup upwards or curl downwards. Later leaf shaped enations appear on the lower side of the leaves from the main vein. Plants remain stunted. Excessive shedding of buds and bolls occur.
The G.arboreum cottons are not affected by this disease. Growing G.arboreum cotton or resistant varieties like RS 8975, LRA 5166, LII 144 are some reliable methods to curtail this disease. Removal of alternate hosts like Hibiscus esculentus, Abutilon sp., Sida alba, Althea rosea and Zinnia sp, should be recommended. The vector Bemesia tabaci should be contained by timely spraying to check further spread of the disease.
Agronomic practices
.Deep ploughing during summer season.
Use of certified seeds of cotton hybrids
Complete sowing in a shortest span of time.
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