Thrips: Silvery Scars and Black Specks on Leaves
By The Budometry TeamPublished Updated
Thrips rasp the leaf surface and drink the contents, leaving silvery, almost metallic scarring. Because part of their life cycle happens in the soil, leaf sprays alone rarely finish the job.
Part of our pillar guide: Plant Training, Pests and Troubleshooting
Identifying
Irregular silver or bronze patches on leaves, tiny black specks of frass, and fast-moving slender insects about 1mm long, often pale yellow or dark.
Treatment
Blue sticky traps for adults, insecticidal soap or spinosad on leaf surfaces in veg, and beneficial nematodes or predatory mites in the soil to break the pupal stage.
Timeline
Plan for three weeks of consistent treatment on a 5-7 day cycle. Stopping when the visible adults disappear is how infestations return.
Frequently asked questions
- Can thrips ruin a harvest?
- They damage leaves more than flower, but heavy infestations reduce photosynthesis enough to cut yield noticeably.
The full guide on this topic
Plant Training, Pests and Troubleshooting
Topping, LST and SCROG explained, plus how to identify and stop spider mites, fungus gnats and powdery mildew, and how to read leaf symptoms correctly.