DISEASE MANAGEMENT:
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Damping off (Pythium, Rhizo ctonia, Phytophthora, etc.)
In pre emergence damping off, the growing points are killed in the initial stages of seed germination before they come out through the soil. In post-emergence darmping off, the seedlings topple over the ground due to collar rotting and rapid shrinking of the cortical tissue of the hypocotyls.
Control measures:
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• Hot water treatment of seeds (at 51.70 for 30 min)
• Treat the seeds with Thiram / Captan / Metalaxyl-Mancozeb @ 2.5-3.0g/kg of seeds.
• Drenching the nursery beds 7 days before sowing with Thiram / Captan or any copper fungicide @ 3g / litre of water.
• Remove the affected seedlings from beds as soon as the symptoms are visible.
TSWV (Tomato Spotted wilt virus):
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• Vector : Thrips
• Browning of Leaves.
• Leaves show bronze coloring
• Bronzed areas roll inward
• Fruit shows numerous spots about 1.2 cm in diameter
• with concentric circular marking.
• Spraying of Thiazofurin can 00 to 200 mg/l(an antiviral agent).
Late blight (Phytophthora infestans (Mont) de Bary) :
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It is serious fungal disease when temperature lay between 100 to 200 C with relative humidity of 85% and above for 18 hours continuously for at least two consecutive days.
Brown to purple black lesions appears on leaflets, petiole or, stem, advanced rapidly to cause a severe blight in favorable condition with white fructification of fungus appears on the lower side of the leaves. Grey water-soaked spots enlarged to indefinite size and shapes appear at stem end of the fruit. If favorable cool moist weather prevails plant may die within 3-4 days.
Control measures:
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• Spray with protectanct fungicides like copper-oxychloride (0.3 %) / mancozeb (0.25 %) / chlorothalonil (0.2%) at 7-10 days interval.
• If late blight is present in field in pockets, start spraying with metalaxyl-mancozeb (0.25%) / cymoxanil-mancozeb (0.25) / dimethomorph (0.1%) + mancozeb (0.2%) immediately, and alternate spray schedule with protectant and systemic fungicides at 7.10 days interval depending upon weather condition.
Early blight(Alternaria solani (Ellis and Mart) Jones and Grout) :
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It is a serious fungal disease when temperature lay between 180 C to 300C and soil moisture is abundant. Circular to angular and dark brown to black spots appear on the leaflets. Usually, a narrow chlorotic halo is found around the necrotic spots. Fruits may be infected both at the green and ripe stage. At stem end, black or dark brown lesions usually develop with sunken spots which becomes leathery later.
Control measures:
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• Spray the crop with 0.3% mancozeb or 0.1% carbendazim or chlorothalonil 0.2% at 10-15 days interval starting from 45 days after transplanting as a prophylactic measure.
• Two sprays of 0.2% chlrothalonil or difenconazole (0.05%) or propiconazole (0.1) is very effective.
Septoria Leaf Blight (Septoria lycopersici):
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• Small brown spots are often visible on tomato leaves
• The spots, usually surrounded by bright yellow halos, start on the lower leaves and gradually appear on upper leaves over time
• Spots often coalesce together, leading to browning and eventual death of entire leaves.
• A close look at the leaves reveals several details. The spots show a dark border that surrounds leaf tissue that has turned light gray. Tiny pepper-like spots are scattered within the gray tissue. The black, pepper-like spots are structures of the fungus that causes the leaf spot disease, Septoria lycopersici.
Management Strategies:
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o Because Septoria leaf spot is favored by wet leaf conditions, any cultural practices that minimize leaf wetness will discourage disease development. Promote good air flow among leaves to assist drying by proper spacing and staking of plants. Also, avoid wetting the leaves when watering.
o Fungicides are available in the market to protect tomato plants from infection. Sprays should begin before disease begins to develop, or at the very first signs of disease. Sprays are typically repeated every 7-10 days. eg Mancozeb @ 0.2%, Captan @ 0.3%
o The Septoria fungus is able to overwinter on diseased plant parts. Good sanitation practices and 3-4 year crop rotation will help minimize the presence of the fungus in your field.
Buckeye rot(Phytopthora parasitica):
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This fungal disease becomes severe becomes when soil moisture is plenty and soil temperature is around 180C. The disease symptoms appear on the lower fruits. A brownish spot appears often at the point of contact betweenthe fruit. A brownish sport appears often at the point of contact between the fruit and the soil. The spot enlarges and the soil. The spot enlarges and the surface of lesion assumes a pattern of concentric rings of narrow, dark brown and wide, light brown bands.
Control measures:
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• Spray the crop 3-4 times with 0.3% copper oxychloride or mancozeb or metalaxyl-mancozeb (0.25%) cymoxanil mancozeb (0.25%) at 10 days interval starting from disease appearance.
Bacterial wilt(Psendomonas solanacearum E.E. smith)
It is a serious bacterial disease particularly in the sandy loam and lateritic soil. Drooping of the lower leaves followed by wilting of the entire plant. Leaf epinasty, marginal leaf necrosis and development of adventitious roots along the stem take place. A slimy grey material oozes out when the stem is cut.
Control measures:
• Treat the seeds with hot water at 520C for 20 minutes or with 0.01% streptomycin solution for 30 minutes.
• Proper crop rotation with non-solanaceaous crops for at least 2 to 3 years reduces the infestation. Effective rotations are maize okra cabbage/cauliflower, maize-beans-maize, or Okra-rice-mustard.
• Apply bleaching powder @ 15-20 kg/ha and 4.5q lime to the land and mix it property to the soil atleast 3-4 week before planting.
• Proper drainage should be maintained..
Tomato leaf curl (TLCV):
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Tomato leaf curl virus is transmitted by vector white fly (Bemisia tabaci). Severe stunting of the plants with downward curling of leaves, crinkling of the leaves and excessive branching are the characteristic symptoms. Older leaves turn leathery and brittle and the newly emerging leaves look pale yellow and smaller in size. In severe infection, the plants remain unfruitful.
Control measures: :
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• Treat the seeds with hot water at 520C for 20 minutes or with 0.01% streptomycin solution for 30 minutes. Destruction of all weeds around the field which serve as alternate host of the virus.
• Cover the nursery bed with 40-60 mesh fine nylon net and spray the seedlings with imidacloprid (3.5 ml/ 10lt).
• Pre-sowing treatment of nursery beds with carbofuran 3G@15g/10 sq.m.
• Apply carbofuran 3G @ 25-30 kg/ha 10 days after transplanting followed by 2-3 foliar sprays with 0.05% dimethoate (Rogar1.5 ml/l) or imidachlorpid (3ml/10 It) or acetameprid (0.3-0.49/lt) or thiomethoxam (3.5 ml /10 lt) at 10 days interval and alternate the spray schedule with NSKE (0.5%).
Tomato mosaic:
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The tomato mosaic virus (TMV) is transmitted by contact with clothes, man, animal and machinery during cultivation or by contact of infected plants, plant debris and through infected seeds. Yellow-green molting appears on leaves and occasionally on fruits. Infected leaflets are usually distorted, puckered and smaller than normal. Number of branches, inflorescence and flowers are substantially reduced.
Control measures:
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• Soak the seeds in trisodium phosphate solution (90 g/l of water) for 15 minutes a day or two before sowing.
• Practice crop rotation excluding solanaceous crops.
Powdery mildew (Leveillula taurica)
- The disease occurs severely during dry seasons.
- A white powdery coating of the fungal growth appears on the leaf surface.
- Infected leaves may be stiff, narrow and smaller in size
- The fungus progressively attacks new leaves, spreading over leaf stems, twigs, and even the fruit
- Terminal growth of the affected shoot is stunted or killed. The fruit yield is reduced and the affected fruit are smaller in size
- Management: Spraying with karathane (0.1%) or wettable sulphur (3 g/ litre of water) twice at an interval of 10 days helps to control the disease
