Tomato thrips is one of the most important insect pests of tomato crop, which causes significant economic losses, both directly and indirectly.
They possess piercing-sucking mouthparts and feed on the mesophyll and epidermal cells of plant tissues.
Thrips can cause damage to tomato harvests by destroying seedlings before they have a chance to become hardy. This is because they thrive on expanding plant tissues.
They thrive in hot, dry conditions and are usually more damaging in areas where these climatic conditions prevail for most of the production season.
Tomato thrips are extremely polyphagous. Apart from tomato crops, they also feed on many field crops, vegetables, various flowers, bedding plants and weedy plants.
IDENTIFICATION
Eggs
They are very small, opaque and kidney-shaped and are usually laid singly in a scattered pattern, but sometimes may occur in rows alongside or beneath veins. They are partially or completely inserted into an incision made into the parenchyma tissue of leaves, flowers or fruit by the saw-like ovipositor of the female.
Eggs are susceptible to desiccation.
Larvae
Larvae and adults are the only feeding stages. The
The
Pupae
There are two non-feeding stages between the larva and adult and both stages have functional legs. The first is the
Adults
They are slender and dorso-ventrally flattened with four wings fringed with long hairs. At rest, the wings are folded over the back lengthwise.
Females have three color forms (pale, intermediate and dark), all of which can mate with the pale males.
Mature adults are approx. 1.5 mm long and pale yellow to light brown in color.
The adults are the only life stage that can fly, but they are not strong fliers. Adult thrips can be carried on wind currents, on clothing, and in association with plants.
LIFE CYCLE
Adult thrips hatch from an egg and develop through two actively feeding larval stages and two non-feeding stages, the prepupa, and pupa, before becoming an adult.
Late-instar larvae change greatly in appearance and behavior and are called prepupae and pupae, even though thrips do not have a true pupal stage.
Females lay their elongate, cylindrical to kidney-shaped eggs on or into leaves, buds, or other plant parts. The pale prepupae and pupae of most species drop to the soil or leaf litter or lodge within plant crevices or galls.
The length of the thrips life cycle from egg to adult varies depending on environmental conditions but is generally 30 to 45 days, though it can be as little as 14 days especially when the weather is warm.
Thrips have several generations in a year.
FEEDING & DAMAGE
Thrips cause direct damage by feeding on the fruits, flowers, leaves, and shoots and very greatly affect crops’ cosmetic appearance.
Affected plants have a stunted growth and the damaged leaves become papery, distorted, develop tiny pale spots (stippling), and drop prematurely.
Flowers and leaves have a characteristic “silvery” appearance and heavy infestation causes flower abortion.
Infested terminals may discolor and become rolled.
Small black fecal deposits (little black spots) may be present in the feeding area.
Damage to plant leaves may also occur when females, using their sharp ovipositor, insert eggs into plant tissue.
They also vector Tomato spotted wilt virus which can wipe out all the tomato plants within no time.
MANAGEMENT
Chemical method
Treatment with foliar insecticide sprays early in the season and continuing through the season as needed helps to control the pest and therefore limit in-field spread of Tomato spotted wilt virus.
A rotation of different classes of insecticides is highly recommended in order to minimize insecticide resistance in thrips.
The following insecticides are recommended for an effective control of tomato thrips;
- ALONZE 50EC 5ml/20l
- PROFILE 440EC 30ml/20l
- DEFENDER 25EC 40ml/20l
- AMAZING TOP 100WDG 5g/20l
- LEXUS 247SC 8ml/20l
- EPITOME ELITE 500SP 10g/20l
- SINOPHATE 750SP 20g/20l
- PRESENTO 200SP 5g/20l
- OCCASION STAR 200SC 5ml/20l
Non-chemical methods
- Avoid planting tomatoes next to onions, garlic, or cereals, because high thrips numbers often build up on these crops.
- Avoid fields near greenhouses where ornamentals (cut flowers) are grown because these plants serve as hosts for the virus and thrips.
- Use of natural enemies like
- Practise rotations with non-host crops
- Plant resistant/tolerant varieties
- Ensure proper weed control
NB; whenever spraying, insecticides should be mixed with INTEGRA 3ml/20l. This is a sticker, spreader, and penetrant which increases the efficacy of the chemical.
