Plant Problem Diagnostic
Thrips: Identification and Management
The short answer
Thrips are tiny, slender insects, roughly 1 to 2 millimeters long and just visible to the naked eye. They rasp plant tissue and feed on flowers and foliage, causing stippling, silvery scarring, and distorted growth. Some species also transmit plant viruses such as tomato spotted wilt, which is why early-season management matters.
Sanitation and weed control are among the most effective and least expensive tools, because weeds shelter both thrips and the viruses they spread. Reduce plant stress with proper watering and good air circulation, use yellow sticky cards to monitor, and conserve natural enemies. Targeted insecticides are a later step; if you suspect a virus or the problem is widespread, confirm the diagnosis with your local Extension office before treating.
Recognizing thrips and their damage
Adult thrips are about 1 to 2 millimeters long, slender, and barely visible. Common problem species include flower thrips and western flower thrips. Feeding produces stippled or silvery scarring on leaves and petals and can distort new growth.
- Tiny (1-2 mm), slender insects on flowers and leaf undersides
- Silvery or stippled scarring and distorted new growth
- Some species spread viruses like tomato spotted wilt
Cultural and monitoring steps first
- Practice sanitation and control weeds, which shelter thrips and viruses
- Reduce plant stress: water when needed and avoid reflected heat and poor air circulation
- Use yellow sticky traps to monitor populations
- Conserve natural enemies (predatory insects, mites, and beneficial fungi)
When to escalate
If monitoring shows populations building or you suspect a virus, targeted insecticide applications or biological control releases may be appropriate. Because virus-carrying thrips are hard to control once established, confirm the situation with your local Extension office before choosing a product, and follow the label.
⚠ Plants infected with a thrips-transmitted virus cannot be cured; remove them to protect nearby plants and focus on prevention.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Maryland Extension — Thrips in Home Gardens — Thrips identification, feeding damage, and home-garden management.
- University of Maryland Extension — Thrips Management in Greenhouses — Species and sizes (1-2 mm), sanitation and weed control as key tools, monitoring, targeted control options.
- University of Maryland Extension — Thrips and Tomato Spotted Wilt Virus — Thrips transmit tomato spotted wilt virus; early-season management and weed control matter.