Integrated Pest Management

Foliar diseases

Alternaria leaf spot

Causal Organism

Alternaria macrospora

Damage

• Small brown, round spots surrounded by a purple margin appear on leaves.
• On older leaves the necrotic center of the spots may be marked by a pattern of concentric zonation.
• Several spots coalesce to form large necrotic areas particularly near leaf margin.
• Under humid weather conditions the spots appear as sooty black leading to premature defoliation.
• The leaf stalk and bolls become infected with spherical or elliptical purple spots.

Cultural Control

• Grow certified acid delinted seeds of resistant varieties.
• Follow recommended agronomic practices for land preparation, stubble management, seed rate, fertilizers and irrigation management. 
• Do not extend the normal crop period and avoid ratooning.
• Avoid dense cropping that helps in reducing the disease incidence by allowing free air current.

Mechanical Control

• Remove and destroy crop residues after last picking.

Biological Control

• Conserve bio agents ( species of Gossypium) like Aspergillus fumigatus, A. niger, Drechslera  halodes, Fusarium culmorum, F. moniliforme, Monilia sitophila, Rhizopus stolonifer and Trichoderma viride.
  

Chemical Control

• Spray mancozeb 2.5 g or copper oxychloride 3g/ litre 4-5 times at 15 days interval.

• Dress the seeds with vitavax or aureofungin or seedex or difolatan or indofil M-45 @ 2-3 g/kg of seeds.

• Spraying with 0.2 per cent difolatan (captafol) or mancozeb at 20 days interval from first appearance is effective in managing the disease.

Anthracnose

Causal Organism

Damage

• The fungus attacks the seedlings, bracts and bolls.
• On cotyledons small reddish spots are formed.
• At collar region elongate reddish brown lesions are formed.
• Bolls of all stages are attacked, initially small water soaked, circular, sunken, reddish brown spots appear and their centers become black as they grow.
• The pinkish-brown spots appear mainly on the underside of leaves. 
• In case of severe infection, area under necrotic region increases and often results in defoliation.

Survival  & Favourable Conditions

• Dense canopy with warm humid weather favours the disease development.

Cultural Control

• Grow certified acid delinted seeds of resistant varieties.
• Follow recommended agronomic practices for land preparation, stubble management, seed rate, fertilisers and irrigation management. 
• Do not extend the normal crop period and avoid ratooning.
• Avoid water logging.
• Avoid dense cropping and collatoral weeds such as Aristolochia  bracteate and Hibiscusdiversifolius.
  

Mechanical Control

• Remove and destroy crop residues after last picking.
• Destroy the infected plant debris..

Chemical Control

• Acid delinted and treat the seeds with carbendazim or benomyl.
• Spray carbendazim 1.5 g/l; OR
  benomyl 1.5 g/l; OR
  Mancozeb 3g/l.

Cercospora leaf spot

Causal Organism

Damage

• First reddish dots appear which ultimately enlarge but retain a narrow reddish margin enclosing a white to light brown centre of dead tissue.
• Later on spots become irregular surrounded by a chlorotic halo.
• Leaves turn yellow and defoliate prematurely.

Cultural Control

• Grow certified acid delinted seeds of resistant varieties.
• Follow recommended agronomic practices for land preparation, stubble management, seed rate, fertilizers and irrigation management. 
• Do not extend the normal crop period and avoid ratooning.

Mechanical Control

• Remove and destroy crop residues after last picking.

Chemical Control

• Spray mancozeb 2.5 g/l or copper oxychloride 3g/ litre 4-5 times at 15 days interval.

Grey mildew / Areolate mildew

Causal Organism

Damage

• The disease first appear on the lower canopy of older leaves when bolls set.
• Irregular, angular translucent spots (areola) are formed by the veins of leaves.
• Leaves become yellow, turn to brown and defoliate prematurely.

Survival & Favourable Conditions

• The pathogen survives mainly in plant debris and volunteer plants.
• High humid favour disease development.

Cultural Control

• Deep ploughing
• Destroy crop residues.
• Grow certified acid delinted seeds of resistant varieties.
• Crop should be rotated with cereals, and preference should be given to tolerant varieties. 

Mechanical Control

• Crop residues should be removed and the fields must be deeply ploughed in order to bury and destroy the remaining plant tissues. 

Chemical Control

• Spray 3 g wettable sulphur
  OR
• 1 g carbendazim or benomyl per litre.
• Dusting by 8-10 kg of sulphur powder effectively controls the disease.
  OR
• Application of 1% Bordeaux DF.
  OR
• Application of 3% copper fungicide 
• Foliar application of sulphur dust/wettable sulphur @ 10 kg/ha or 2-3 g/l at 10 days interval from the day of first appearance, or sulphex 80 WP (0.25%) or benomyl, carbendazim @ of 200-300 g a.i. /ha is effective in controlling the disease significantly.

Helminthosporium leaf spot

Causal Organism

Damage

• Lower leaves of seedlings turns light yellow which increase in size, become dark brown and 
  surrounded by a dark purple border.
• The centre of the spots become ashy and shed off leaving shot holes. 

Cultural Control

• Grow certified acid delinted seeds of resistent varieties.
• Follow recommended agronomic practices for land preparation, stubble management, seed rate, fertilisers and irrigation management. 
• Do not extend the normal crop period and avoid ratooning.
• Avoidance of dense cropping helps in reducing disease incidence as well as intensity.

Mechanical Control

• Remove and destroy crop residues after last picking.

Chemical Control

• Spray mancozeb 2.5 g/l or copper oxychloride 3g/ l 4-5 times at 15 days interval.
• Foliar spray of thiobendazole or copper oxychloride @ 0.2 per cent controls the disease. However, a number of other fungicides such as zineb, ziram and captan are effective in controlling the secondary spread of this disease.

Soil-borne disease

 Fusarium wilt

Causal Organism

Damage

• The symptoms first appear on the cotyledons vein starts darkening, followed by peripheral 
  chlorosis. The cotyledons become progressively more chlorotic and then necrotic before being 
  shed. 
• In older plants, the first external evidence of infection is yellowing of margin of one or more 
  lower leaves. 
• As the disease progresses within the plant, more leaves develop chlorosis, which characteristically 
  appears in patches between the main veins where as rest of the leaf remaining green.
• Leaves droops, dry and shed off.
• Ultimately plant dies causing 100% mortality.

Survival & Favourable Conditions

• The fungus is soil borne. Nematodes attacking cotton predispose the crop to wilt disease.

Cultural Control

• Deep ploughing.
• Grow resistant varieties.
• Intercrop with moong bean/ragi/ soybean/ groundnut/ maize/ cowpea/ onion.
• Fields with long history of disease should be avoided for growing the crop.
• Use of nitrogen fertilizers, particularly ammonium nitrate should be discouraged while use of potassium fertilizers should be encouraged

Mechanical Control

• Destroy crop residues.

Biological Control

• Treat the seed with 4 g Trichoderma viride formulation/ thiram 3g per kg seed.
• Apply 2 kg of Trichoderma viride commercial formulation with 50 kg farm yard manure along with the rows.

Chemical Control

• Spray of 0.4% solution of oxathilin.
  OR
• 0.1% solution of organomercuria.
• Seed treatment with carbendazim @ 2 g/kg seeds should be given

New wilt

Damage

• The wilt generally appears at flowering and boll development stages and plants show drooping 
  of leaves which start from the crown downwards.
• There is partial epinasty, drooping of lamina, reddening of leaf surface, petiole, stem and branches without chlorosis or necrosis and without loss of turgor. 
•  Leaves shed and some plants show partial recovery whereas others may die. 

Cultural control

• Growing late maturing genotypes.
• Promotion of arboreum species which are known to be relatively tolerant to moisture stress.
• In drought conditions, irrigation can reduce the disease incidence.
• Judicious water management throughout the cropping season and particularly during the dry spells and soon after the cessation of the rainfall.
• Complete field and crop sanitation.
• Scrapping around cotton plants for aeration and revival in case of wet conditions.

Chemical Control

• Drenching of cotton plants with 2% urea for dry conditions.

Root-rot

Causal Organism

Damage

• Circular yellowish black patches are seen on seedlings or wood.
• Root tips are discoloured and black dot size sclerotia develop on the woods which rot.
• The most common symptom is dry or wet dark rot of the lower stem. 
• On split opening, the affected plant can be easily distinguished by discoloured stele of main root and pith of stem. 
• In severe cases, there is dissolution of stem and root tissues.
• Sudden and complete wilting of the plant.

Survival & Favourable Conditions

• The plant suffer high mortality at soil temperatures 39 degree C.

Cultural Control

• Intercrop with moth bean.
• Grow resistant variety.
• Deep ploughing.
• Avoid mono-cropping and cultivation of cucurbitaceous and solanaceous crops, in adjoining fields.
• Fields having long history of disease should be avoided for sowing. 
• Field should be deeply ploughed and left for solarization.
• Early sowing and harvesting is recommended to avoid extreme temperatures. Sowing in April or June instead of May reduces disease incidence.
• Crop should be rotated. Intercropping using Vigna acontifolia reduces the incidence quite significantly.

Mechanical Control

• After harvesting, either plant debris should be completely buried or removed. 
  

Chemical Control

• Treat the seed with benomyl or carbendazim @2.5 g/ kg seed.
• Apply 2 kg of Trichoderma viride commercial formulation with 50 kg farm yard manure along with the rows.
• Seed dressing with bio-pesticide preparation of Trichoderma viride or Gliocladium virens or with brassicol + captan and carbendazim slurry effectively reduces the disease incidence.
• Green manuring with Sesbania acubeata + planting during second week of July, and application of ammonium sulphate and intercropping with moth (Vigna aconitifolia) considerably reduce the 
  disease incidence. 

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Bacterial Disease

Bacterial blight

Causal Organism

Damage

• The larvae feed gregariously on the under surface of the leaves and skeletonize them
  leaving only the mid-rib and veins in severe cases. 
• They also attack flowers, buds and squares causing considerable loss.

Cultural Control

• Plough deeply to expose the pupae and hibernating larvae.

Mechanical Control

• Mechanical collection when larvae are feeding in groups, i.e., the younger larvae.
• Collection and destruction of egg masses. 
• Set-up pheromone traps.

Biological Control

• Release egg parasitoids Trichogramma sp. (1.5 lakh/ha) and larval parasitoids Chelonus blackburni or Telenomus remus or Bracon sp.
• Release of predators Chrysoperla carnea @ 50,000 /ha.
• Spray Spodoptera NPV @ 250 LE/ha.
• Apply B.t.k. @ 1 kg/ha.

Chemical Control

• Spraying of insecticides endosulfan 35 EC @ 600-750 ml/ ha effectively reduces the population.
• Spraying synthetic pyrethroids fenvalerate 20 EC @ 400-500 ml/ha or cypermethrin 10 EC or 
  decamethrin 2.8 EC @ 600 - 700 ml/ha is also effective.