Caterpillars on Cannabis (Budworms)
Cannabis caterpillars — usually corn earworms or tobacco budworms — bore INTO buds and eat them from inside. By the time you see damage, they're already eating your harvest.
What it looks like
- ●Small holes in leaves (early)
- ●Dark crumbly frass (poop) in bud crevices
- ●Wilting buds with brown rotten spots
- ●Small green worms inside buds when you inspect
Quick diagnostic checks
Measure before you treat
Plant diagnostic essentials
These tools help confirm the cause of caterpillars / budworms before you change nutrients, watering, or the environment.
Carson MicroBrite Pocket Microscope
Inspect leaf undersides for mites, eggs, mildew, and harvest-ready trichomes.
Check price on AmazonGovee Bluetooth Hygrometer
Track temperature and humidity trends instead of guessing from one reading.
Check price on AmazonAC Infinity CLOUDLINE T4
Automate airflow to manage heat, humidity, and mold pressure.
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Causes ranked by likelihood
1. Outdoor grows are primary target
Most commonSigns
- ●Growing outdoors
- ●Moths visible at dusk
Fix
- ✓Apply Bacillus thuringiensis (BT) spray weekly from pre-flower
- ✓BT is safe for plants and only kills caterpillars
- ✓Inspect buds daily during flower
Recommended products
Captain Jack's BT Spray (Bacillus thuringiensis)
The gold standard for budworms — harmless to plants, only kills caterpillars
⚠️When to worry
Always. Caterpillar damage turns into bud rot within days. Can destroy an entire outdoor harvest.
Gear that prevents this problem
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