Thrips

While over 6000 species of thrips exist worldwide, only ten per cent are deemed to have an economic impact on crops. The most common group is Terebrantia, which includes many of the damaging species such as onion thrips, western flower thrips and plague thrips. Hosts include citrus, green beans, cotton, mungbeans, cereals, some vegetables, summer pulses, sunflowers, canola and peanuts. Thrips can be vectors for tobacco streak virus and tomato spotted wilt virus.

Description

Thrips are small (2 mm), with a slender, cigar-shaped body with fringed wings. Colours range from pale to dark brown and sometimes black. The larvae are similar in appearance to adults however are smaller, pale and wingless.

Eggs are usually laid into plant tissue, although some species will lay eggs on the plant surface. Most species pupate in leaf litter whilst others pupate on protected parts of the plant, such as flowers.

Thrips have tiny needle-like mouthparts which puncture the outer layer of plant cells to suck the sap.

Affected leaves tend to have a silvery-white appearance and younger leaves can become distorted and growing points may die. Feeding damage to fruit can cause blemishes and fruit scarring, resulting in quality downgrades.

Control

As some thrips such as western flower thrips and onion thrips can develop resistance quickly, it is important not to rely on insecticides alone. Natural predators of thrips include pirate bugs, lacewing larvae and ladybird beetles, therefore encouraging these populations will assist in keeping thrips populations low. Avoiding applications of broad spectrum, residual chemicals is important in maintaining these beneficial insect populations.

Regularly monitoring plants for evidence of thrips damage, managing host weeds and planting resistant or tolerant crop varieties will assist in reducing economic losses. Also, turning in harvested residues in crops such as green beans, may assist in killing any thrips that may be present pupating in the soil.

Thrips often occupy protected areas such as flowers, growing tips and leaf curl galls. Consequently, systemic pesticides can be more reliable for control compared to contact pesticides which only control thrips present on the plant surface.

Movento® is ideal for controlling sucking pests which hide in protected parts of the plant and is also soft on most beneficial species when used as directed. Movento is registered for control of western flower thrips in beans (green), celery, rhubarb, eggplants, peppers, tomatoes, herbs, bulb vegetables (excluding bulb onions) and lettuces. It is also registered for control of tomato thrips in beans (green), celery, rhubarb, bulb vegetables (excluding bulb onions), and herbs. Registration for control of plague thrips exist in celery, rhubarb, herbs and provides suppression only in grapes. It is also registered for Kelly’s citrus thrips in citrus and for onion thrips in bulb onions and bulb vegetables. Lastly, it is also registered for suppression of northern plague thrips in grapes.

Movento® Energy is registered in bananas for the control of banana rust thrips.

References

Broughton, S (2018), ‘Thrips in citrus’, Department of Primary Industries and Regional Development

Duff, J and Manners, A (2016), ‘Thrips: A pest management plant for productions nurseries’, Horticulture Innovation Australia, https://www.horticulture.com.au/growers/help-your-business-grow/research-reports-publications-fact-sheets-and-more/thrips-a-pest-management-plan-for-production-nurseries/

Duff, J and Manners, A (2017), ‘What are Thrips’, Horticulture Innovation Australia, https://www.horticulture.com.au/growers/help-your-business-grow/research-reports-publications-fact-sheets-and-more/thrips-fact-sheet/

Queensland Government (2018), ‘Thrips’, https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/crop-growing/pests-field-crops/thrips