Western Flower Thrips

What is it?

Western flower thrips is one of the world's most damaging and insecticide-resistant thrips. It feeds inside flowers and buds and on young tissue, and is a key vector of tospoviruses such as tomato spotted wilt — so disease risk compounds the feeding damage.

How to identify it

• Tiny (~1-2 mm) slender insects, pale yellow to brown, hiding in flowers, buds and growing points.
• Silvery, stippled or scarred leaf and petal surfaces with tiny black frass specks.
• Deformed flowers, scarred fruit and distorted new growth.
• Sudden tospovirus symptoms (ring spots, necrosis) signalling thrips-vectored virus.

Life cycle & spread

Very short life cycle with many overlapping generations; pupation often in the soil/media. Rapid turnover is why resistance develops quickly under repeated single-chemistry use.

Conditions that favour it

Warm conditions, flowering crops and protected (greenhouse) environments favour explosive build-up; nearby flowering weeds are reservoirs.

Damage and how it spreads

Direct scarring downgrades flowers, fruit and foliage; tospovirus transmission can cause losses far beyond the feeding damage, sometimes destroying whole plantings.

Monitoring & scouting

Use blue/yellow sticky traps and flower tapping to detect early; scout buds and growing points; act on larvae before populations and virus spread build.

How to control it

1. Target the exposed larval and adult stages with thorough coverage of flowers and growing points;
2. rotate modes of action;
3. remove flowering weed reservoirs;
4. use a natural mode of action to slow resistance.

Preventing it next season

Sticky-trap monitoring, weed/reservoir management, mode-of-action rotation, and early treatment before flowers and virus spread build.

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