Tomato Spotted Wilt Virus: Tomato is one of the commercial crops grown by Indian farmers .Tomato crop can be infected by viruses and TOSPOW Virus the most serious one.
TOSPOW Virus, which is transmitted by thrips, causes serious loss in economically important crops and it is one of the most economically devastating plant viruses in the world. The TOSPOW is said to be transmitted by at least ten different species of thrips.
TOSPOW virus occurs in all stages like Nursery/ Seedling, Vegetative/Tillering, Flowering/Panicle, Fruiting, Harvest stages. The disease spreads more during hot months of the year with high relative humidity because it is associated with a high population of insect vectors (thrips) during hot season.
Symptoms Of Tomato Spotted Wilt Virus Disease
- Stunting of new growth later the young leaves turn to bronze in colour or leaves may have prominent purple veins.
- Appearance of dark purple to brown ring spots on the leaves. As and when the bronzing area expands on the leaves, the upper foliage becomes twisted and cupped.
- Dark brown streaking develops on the terminal stems.
- The younger plants may start to wilt and ultimately die under severe diseased conditions, but the older plants may survive and bear fruits which get discolored and may not fully ripen.
- In the case of fruits, light green color ring spots on green fruits will be seen and the spots will be more clear with yellow color on ripe fruits.
- Raised bumps on affected areas of fruits.
- Fruits will get deformed and ripen unevenly.
- If the plant is affected at earlier stage, it does not bear any fruits at all.
Causes Of Tomato Spotted Wilt Virus
- The disease spreads during hot months of the year with high temperature with high relative humidity because it is associated with high population of insect vector (thrips) during hot periods.
- Use of more quantities of ammoniacal nitrogen[Urea, Ammonium Sulphate, 19:19:19 …etc] to the crops. The extent of infection even depends on the high levels of Nitrogen and lower levels of Boron in the soil
- Use of improperly decomposed organic manure, poultry manure, Sheep and goat manure.
- Environmental conditions including high temperature, day length (short day) and low light intensity as well as variety (Susceptible), age of the plant (younger) during infection all will decide the severity of infection.
- The infection mostly occurs in plants grown in seedbeds and transplanted as the chances for entry of virus will be more during handling processes of seedlings.
- The virus will remain in weeds and spread by insect vector mainly by thrips. Warm temperatures during hot dry parts of the year, tends to increase in thrips population which favours the development of Tospow and further spreading.
- The thrips move from plant to plant, while feeding on the infected plant it carries virus and transfers to other healthy plants while feeding it.
- Use tolerant varieties.
- Use virus free planting material for planting.
- Remove all the infected plants and destroy (burn) at early infection stages to avoid spread.
- Control the weeds otherwise they act as alternate host for both virus and thrips which in-turn easily transfer virus from one season to next cropping season.
- Maintain hygiene in the field by destruction or removal of old crops by ploughing or physical removal otherwise the affected debris may act as source of infection.
- Control the insect vector population.
- Following crop rotation.
- Avoid planting near crops which are infected with Tomato spotted wilt virus (ToSPOw).
Use reflective mulches to repel the insect vector population (Thrips).
Normally viral diseases can’t be cured, they can only be managed. As discussed earlier TOSPOW Virus infected plants may lose a lot of flowers or may not flower.The TOSPOW Virus disease can be managed by application/ supplying of certain plant growth promoters to strengthen plants to fight against TOSPOW Virus and make them flower. Along with growth promoters an insecticide to kill the thrips can be added to prevent further spread.
Sprays that may be applied:
Regent-2ml/lt +Econeem plus -1ml/lt
2nd spray: after 7- 8 days
Perfekt-1ml/lt + Sambrama-1 tablet in 15 liters of water + Econeem plus -1ml/lt
3rd spray: after 7- 8 days
V-bind viricide or no virus-2ml/lt + Magnum mn - 0.5gm/lt of water
Sprays must be applied on both sides of the leaves.
Subject Matter Expert
BigHaat Agro PVT.
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