Clusters of soft, pear-shaped insects on stems or leaf undersides
Colonies grow fast on new growth and undersides; white shed skins and honeydew follow..
- Also called
- aphids
- green bugs on plant
- little bugs on stems
- clusters of insects under leaves
Likely causes, most likely first
Ranked for this sign on its own. Your stage, medium and readings change the order, so run the checker for your plant.
LikelyAphids
Fix: Squash or rinse small colonies; release parasitoid wasps (Aphidius), predatory midges or lacewings; insecticidal soap or oil only before flower. Control ants that farm them.
Recovery: Colonies shrink and mummified (parasitised) aphids appear within 1-2 weeks.
How to confirm it
- Magnifier check of leaf undersides and new growth. Use a 10-20x loupe for spider mites, thrips, aphids and whiteflies, and a 30-60x lens or clip-on phone macro for broad and russet mites. Check the undersides of 10 affected leaves across several plants and the newest shoot tips, in white light. Look for moving dots, eggs, shed skins, webbing, slender insects with black specks, and glassy specks on new growth.
- Sticky cards for 1-2 weeks. Hang yellow cards at canopy height and lay one flat on the medium surface; add blue cards for thrips. Count catches every 3-4 days. Rising counts of small dark flies at the medium mean fungus gnats; slender insects mean thrips; white wedge-shaped fliers mean whiteflies; winged aphids mean a colony nearby.
Look for
Groups of soft-bodied insects with tailpipes (cornicles), white cast skins nearby..
The full guide: Aphids on cannabis: species, life tables, population growth and IPM
Guidance, not a guarantee. The checker weighs common causes against what you tell it; confirm with the tests before you treat, change one thing at a time and watch the new growth.
