Tomato

Disease Management

Anthracnose Bacterial Spot Bacterial Wilt Bacterial Canker Buck Eye Rot Collar Rot Damping Off Early Blight Fusarium Wilt Leaf Curl Mosaic Powdery Mildew Potato Virus Rots Spotted Wilt Septoria Leaf Blight Stemphyllium Leaf Spot

Anthracnose Colletotrichum gloeosporioides

  • Primarily a disease of ripe and over ripe tomato fruits. If left uncontrolled, results in serious losses of yield and fruit quality.

Symptoms


Circular lesions


Black specks


Lesions on stems
and leaves


  • Fruit may be infected when green and small, but symptoms do not appear until it begins to ripen.
  • Symptoms first appear on ripe fruits as small, slightly depressed circular lesions.
  • Lesions may enlarge to 12 mm in diameter and become more sunken, with concentric ring markings.
  • Centre of the lesion is usually tan, and as the lesion matures becomes dotted with small black specks.
  • Surface of the mature lesion remains smooth and intact.
  • During moist weather, masses of salmon-coloured spores may be present on the lesion surface.
  • Lesions may also occur on stems, leaves and roots.
  • Small, circular, brown lesions surrounded by yellow halos characterize leaf infections.
  • Fungus survives in association with crop debris and infects fruit resting on the soil surface.

Control

  • Crop rotation with non-solanaceous crops, weed control, staking plants and mulching help in reducing losses.
  • Spraying Mancozeb 2.5 g/l or Carbendazim 1 g/l gives effective control.

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Bacterial spot Xanthomonas campestrisPV. vesicatoria

Symptoms


Irregular spots on leaf


Irregular spots on leaf


Raised spots on fruits

  • Disease first appears as small circular to irregular water-soaked areas showing as definite spots on the lower leaf surface.
  • The spots become depressed with a corresponding bulge on the lower surface.
  • This bulging portion is first smooth but becomes rough later.
  • A narrow yellow halo may surround the spots.
  • When the spots are too many, the interveinal tissues become dry and brown.
  • If the spots are at the edge, they may break away.
  • The leaves may become twisted.
  • Sometimes the petioles and young stems are also affected.
  • On green fruits dark coloured raised points appear sometimes surrounded by water soaked border.
  • The bacterium is seed-borne and also subsists in infected plant debris.
  • Splashing rains are the chief means of local dissemination of bacterium from the ooze developing on the affected parts.

Control

  • Field sanitation and crop rotation reduces the disease incidence.
  • Spraying the plants with a mixture of Streptocycline 200 ppm and Copper oxychloride 3g per litre of water gives fairly good control of the disease.

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Bacterial Wilt Pseudomonas solanacearum

  • Deadly disease of tomato.
  • Tomato cultivation has been abandoned in some parts of India because of this disease.

Symptoms


Wilting of Plant


Stunting Plant


Yellowing of entire plant


Brown vascular
system

  • Wilting, stunting, yellowing of the foliage and finally collapse of the entire plant are the characteristic symptoms of the disease.
  • The lower leaves may droop first before wilting occurs.
  • The vascular system becomes brown.
  • If a segment of the lower stem is cut and squeezed it yields bacterial ooze.
  • Development of adventitious roots from the stem is considerably enhanced.

Control

  • The pathogen is soil-borne, persistent for long periods and very difficult to control.
  • Crop rotation with Cruciferous vegetables is recommended.

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Bacterial Canker Corynebacterium michiganensis

Symptoms


Wilted plant


Water soaked spots


  • Symptoms on the leaves may be unilateral, the leaflets on one side of the rachis being wilted while those on the opposite side appear healthy.
  • On green fruits the secondary infection causes water soaked spots, which soon become surrounded with a white halo.
  • Persistent white halo differentiates canker from bacterial spot.
  • Split open stem lengthwise, show a creamy white, yellow brown line.
  • Disease spreads through the seed, infected debris, in soil, and some solanaceous weed such as Solanum nigrum.

Control

  • Extraction of seed through fermentation, pulp at room temperature for 72 hours eradicates the bacterium from the seed.
  • A 3-year rotation is recommended against the soil borne inoculum.

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Buck Eye Rot Phytophthora parasitica

  • Destructive disease on tomato in areas where moisture is plentiful and favorable temperatures.
  • In tomato, buckeye rot of fruits is very conspicuous.
  • The fungus also attacks beans, brinjal, onion, chillies and pumpkin

Symptoms

  • Spots on fruits are marked with pale brown concentric rings.
  • These spots may be small or Cover a major portion of the fruit surface.
  • There is no rotting of the skin but internal flesh may be discoloured upto the core.
  • When green fruits are attacked they show brownish circular spots at the blossom end, shrink and are mummified.
  • The pathogen survives in soil for many years through oospores and chlamydospores.

Control

  • Crop rotation, destruction of weeds, good soil drainage, selection of light soil, seed treatment and spraying in the seed bed as well as in the field are important for management of the disease.
  • Seed treatment with Captan or Thiram at 3 g per kg seed and spraying with Mancozeb at 2.5 g/l are effective and most economical.
  • Staking of plants, removal of lower foliage (upto 30 cm) and fruits helps in prevention of initiation of the disease and its spread.

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Collar Rot Sclerotium rolfsii

  • Soil borne disease, occurs under adverse conditions for growth of tomato plants in warm weather.

Symptoms

  • Base of the stem near soil line and fruits that come in contact with soil show tissue necrosis. on which fungal mycelium and sclerotia can be seen.
  • Sudden wilting of the plant occurs.

Control

  • The pathogen is soil-borne.
  • Seed treatment with 4 g Trichoderma viride formulation per kg seed is helpful in reducing the incidence of the disease.
  • Drenching soil at the base of the affected plant with Cheshunt compound 3 g/l checks spread.

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Damping Off Pythium aphanidermatum, Rhizoctonia solani

  • Common in many parts of India, occurring in tomato nurseries, and among others, Tobacco, Chillies, Cabbage, Cauliflower, Brinjal and Cucurbits.

Symptoms


  • The fungus attack usually starts on the germinating seed, spreading to the hypocotyl, basal stem, and developing taproot.
  • Young seedlings are killed before they emerge through the soil surface.
  • Seedlings when infected appear pale green with brownish water-soaked lesions at the basal portion of the stem.
  • The lesion girdles the stem, affected tissues rot and the seedlings collapse.
  • In nursery plot the disease may start in patches and in two to four days the entire lot of seedlings may be destroyed.

Control

  • Partial sterilisation of the soil by burning trash on the surface, providing better drainage, forming raised beds and thin sowing are the cultural practices recommended.
  • Seed treatment with 3 g Thiram or 4 g Trichoderma viride formulation plus 6 g Metalaxyl per kg seed or drenching the soil with 1 per cent Bordeaux mixture or Captan 2 g/1 or Metalaxyl (Ridomil MZ) 2 g/1 at 8-10 days intervals, until the seedlings are ready for transplanting, protects them from damping-off.

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Early Blight Alternaria solani

  • Common disease of tomato occurring all over India.

Symptoms


  • The fungus attacks the foliage causing characteristic leaf spots and blight.
  • The disease first becomes visible as small, isolated, scattered pale brown spots on the leaf.
  • Zonate lesions may also develop on stem and fruits.
  • Fully developed spots are irregular, brown to dark brown in colour, and with concentric rings inside the spot.
  • Often several spots coalesce to form large patches resulting in the leaf blight.
  • Lowest leaves are attacked first and the disease progresses upwards.
  • In severe attacks the entire plant may be defoliated.
  • The pathogen survives in soil on diseased plant debris.

Control


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Wilt Fusarium oxysporum f.sp. Lycopersici

  • Worst disease of tomato occurring all over India. Disease is severe in areas where tomato is grown continuously.

Symptoms


  • First symptoms appear as clearing of the veinlets and chlorosis of the leaf.
  • Soon the petiole and leaves droop and wilt.
  • The younger leaves may die in succession and the entire plant may wilt and die in the course of a few days.
  • When plant roots and basal stems are split open dark brown or black discoloration of the vascular tissues may be seen.
  • Fungus survives saprophytically in soil.

Control

  • Crop rotation with non-Solanaceous crops and summer ploughing reduces disease incidence.
  • Seed treatment with 4 g Trichoderma viride formulation or 2.5 g Carbendazim per kg seed is effective.

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Leaf Curl Tomato leaf curl Virus

  • Leaf curl is an important disease in the post rainy and summer tomato.

Symptoms


Stunting and rolling
of leaves


  • The leaf curl is characterised by severe stunting of the plants with downward rolling and crinkling of the leaves.
  • Partial or complete sterility of the plant is also common.
  • Newly formed leaves show chlorosis. The older, curled leaves become leathery and brittle.
  • Plants are stunted due to shortening of the internodes.
  • Diseased plants look pale and produce more lateral branches resulting in bushy growth.
  • The disease is transmitted by the whitefly, Bemisia tabaci.

Control

  • Use of systemic insecticide such as Dimethoate (0.05 % ) as spray or Carbofuran or Phorate granules (50 kg / ha) as soil application are useful in vector control and reducing the disease.

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Tomato Mosiac Tobacco mosaic virus, Cucumber mosaic virus

Symptoms


Mottling of leaves

  • The common symptom of mosaic is mottling of the leaves.
  • The normal green colour of the leaf is interspersed with light green to pale yellow islands of irregular patches.
  • The green parts continue growing while yellowish parts are slow in growth.
  • As a result the normal green patches tend to be sunken or cup-like and gives the leaf a roughened appearance.

  • The edges of the leaf turn downward and are stiffer than those of a healthy leaf.
  • Circular, chlorotic rings appear on the fruit.
  • The virus is sap transmissible and in the field it is transmitted by rubbing between diseased and healthy leaves.
  • Mechanical transmission by insects also occurs.

Control

  • Use of virus-free seedlings and hot water treatment of seed (50 ° C for 25 min.) or seed treatment with 20 per cent Trisodium orthophosphate solution are effective.

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Powdery Mildew Leveillula taurica

Symptoms


Necrotic spots


Lesions on leaf


  • The most common symptoms are light green to bright yellow lesions on the upper leaf surface.
  • Necrotic spots sometimes with concentric rings may develop in their centres.
  • A light powdery covering of these lesions may occur on the lower surface.
  • Under favorable conditions powdery growth is seen on the upper and lower leaf surfaces.
  • Heavily infected leaves die but seldom drop from the plant.
  • The fungus has a wide host range and probably over winters in cultivated and weed hosts.

Control

  • Apply Tridemorph or Dinocap at 1 ml/l or Hexaconazole 2 ml/l for effective control.

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Potato Virus

  • Field symptoms of the disease can be more severe, consisting of dark brown, dead areas in the laminae of nearly mature leaflets.
  • The terminal leaflets may show severe necrosis, and in many cases all leaflets are affected.
  • Subsequently formed leaves exhibit mild Rugosity, slight distortion, and a mild mottle.

  • Leaflets of plants infected are rolled downward with curved petioles, giving the plant a drooping appearance.
  • The virus is readily transmitted mechanically and also by many aphid species.
  • Myzus persicae is the most efficient vector.

Control

  • Methods that serve to delay the entry of primary inoculum into the crop are
    1. Isolation of tomato plantings from areas used to produce earlier tomato and pepper crop.
    2. Planting in areas less likely to support aphid population and virus reservoirs.
    3. Spraying with insecticide to reduce the frequency of transmission.

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Black mold rot Alternaria alternata, Stemphylium botryosum

Symptom

  • Lesions sunken or slightly flattened, water soaked in appearance.
  • May or may not have delimit margins.
  • Soon they become brown to black in colour.
  • The surface of lesions becomes covered with a dense, dark grey to olive green to black covering of Conidia and Conidiophores.
  • Black mold rot fungi are primarily saprophytic.

Soil rot

  • Tomato fruits coming in contact with the soil are attacked by soil-borne fungi causing rotting of the fruits.

Sour Rot Geotrichum candidum, Geotrichum penicillatum

Symptoms

  • Greasy, water soaked lesions begin at wounds or at the edge of the stem scar in green and ripe fruit.
  • In ripe fruit, a white to dirty white, crusty, yeast-like growth develops at breaks in the fruit surface associated with lesions.
  • These fungi are common inhabitants of soil.

Rhizopus Rot Rhizopus stolonifer

Symptoms



  • Lesions begin as rapidly enlarging, water-soaked areas located adjacent to wounds, stem scars, or open stylar pores.
  • Lesions are soft and somewhat watery.
  • Under high humidity, greyish white masses of mold structures develop over the surfaces of diseased fruit.
  • The fungus is wide spread and a common saprophyte.

Blossom end rot Physiological disorder

Symptoms



  • Blossom end rot begins with light tan, water- soaked lesions which then enlarge, turn black and leathery and often become over run with secondary black mold.
  • The disease generally occurs at the blossom end of the fruit.
  • However, it can occasionally occur at the side, and sometimes it produces an internal black lesion not visible from the exterior of the fruit.
  • Fruit affected by blossom-end rot ripens more rapidly than normal.
  • A localized calcium deficiency at the distal end of the fruit results in blossom-end rot.

Control

  • Liming with dolomite or high calcium limestone 2-4 months before planting can alleviate blossom-end rot.
  • During the growing season, foliar sprays of anhydrous calcium chloride may be helpful.

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Tomato Spotted Wilt Tomato spotted wilt virus (TSWV)

  • Recently, it has become the most destructive disease of tomatoes and several other crops.

Symptoms


Dark spots



Concentric rings on fruit


Streaks on stem

  • Affected plants may have a one sided growth habit or may be entirely stunted and have drooping leaves, suggesting a wilt.
  • Plants infested early in the season may produce no fruit, and those, infected after fruit set produce fruit with chlorotic ring spots.
  • Symptoms of spotted wilt vary, but young leaves usually turn bronze and later develop numerous small, dark spots.
  • The chlorotic lesions are highly visible at full colour of the fruit.
  • Weed and perennial ornamentals are important reservoirs of the virus.
  • Disease spreads in the field by the Thrips, Frankliniella schultzei, F.occidentalis and F.fusca.
  • Seed transmission has also been reported in tomato.
  • Growing tips may die-back and stems of terminals may be streaked.
  • Green fruit has slightly raised areas with faint concentric rings, on ripe fruit these turn into obvious rings, which become red and white or red and yellow

Control

  • The infected plants should be rouged out and destroyed.
  • Control of Thrips with insecticides may restrict the spread of the virus.
  • Application of Carbofuran granules ( 100 g/m2) in the nursery and in the main field (15 kg / ha) 10 days after transplantation gives good protection.

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Septoria Leaf Blight Septoria lycopersici

  • Major disease of tomato throughout India.

Symptoms


  • In young plants numerous spots appear on older leaves or on plants with poor growth.
  • Small, circular spots are first observed as water soaked areas on the under surface of the lower leaves.
  • As the spots enlarge, they develop dark brown marking and sunken, white or grey centres with pycnidia.
  • The fungus remains active in soil for at least three years and can also perennate through weed hosts.
  • Two to three days of cloudy weather or drizzle favour the development of the disease.

Control

  • Seed treatment with thiram at 2.5g per kg seed and weekly spray of Zineb at 2.5 g/l in the nursery bed and in main field help in reducing the disease incidence.

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Stemphylium Leaf Spot Stemphylium solani S. Lycopersici

  • This is common worldwide on field tomatoes.

Symptoms


  • Leaf spots appear on the under side of leaves as small brownish black specks.
  • Later these specks develop on both leaf surfaces into greyish brown, glazed lesions.
  • On older leaves lesions dry up, crack and the centres drop out leaving a shot hole appearance.
  • Yellowing of the leaf occurs followed by defoliation of the plant.

Control

  • Foliar application of Mancozeb 2.5 to 3 g/l proves effective.

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Telangana