Aphids significantly weaken cannabis plants. Complete instructions for control and prevention.
Aphids are common cannabis pests that are easily treatable if recognised early:
Recognise aphid species:
Green aphids:
- Most common species on cannabis
- 2-4mm small, green insects
- Form large colonies
- Favour young shoots and leaves
- Multiply explosively
Black aphids:
- Dark to black colouring
- Often on stems and leaf stalks
- Harder to control than green ones
- Transmit viruses more frequently
- Favour cooler conditions
White/grey aphids:
- Rarer, but very harmful
- Mostly on roots (root lice)
- Difficult to detect
- Cause wilting and growth disorders
- Systemic treatment necessary
Understanding damage patterns:
Direct damage:
- Sting and suck plant sap
- Leaves curl upwards
- Yellow, curled leaf tips
- Slowing of growth
- Weakening of the entire plant
Honeydew problems:
- Sticky, sweet excretions
- Attract other pests
- Promote sooty mould fungi
- Block stomata (stomata)
- Reduce photosynthesis
Virus transmission:
- Aphids transmit plant viruses
- Mosaic virus common
- Irreversible damage
- Destroy infested plants
- Prevention reason no. 1
Quick first aid:
Spraying with water:
- Powerful jet of water
- Rinse aphids from plant
- Repeat daily
- Particularly effective for light infestations
- Can be combined with other methods
Soapy water spray:
- 10ml mild detergent per litre
- Thoroughly clean upper and lower leaf surfaces
- leave on for 15 minutes
- Rinse with clear water
- Daily until infestation is gone
Alcohol spray:
- 70% isopropanol with water 1:1
- Spray directly on aphids
- Kills on contact
- Apply only selectively
- Not in direct sunlight
Biological antagonists:
Ladybirds:
- Eat 50-100 aphids per day
- Larvae even more effective than adults
- Can be bought in garden centres
- Also buy eggs (larger population)
- Need more food after aphid elimination
Lacewings:
- Larvae are "aphid lions"
- Eat up to 200 aphids
- Very effective against all species
- Adults are harmless
- Long-term effect
Gall midges:
- Specialised on aphids
- Very small, inconspicuous beneficial insects
- Larvae live in aphid colonies
- Aphidoletes aphidimyza (available for purchase)
- Also active at low temperatures
Ichneumon wasps:
- Parasitise aphids
- Lay eggs in aphids
- Larvae eat aphids from the inside
- Aphidius species very effective
- For long-term control
Organic sprays:
Neem oil formulation:
- 5ml neem oil + 2ml emulsifier per litre
- Systemic and contact action
- Spray every 5-7 days
- Also preventive effect
- Not harmful to bees
Garlic chilli extract:
- 5 cloves of garlic + 2 chilli peppers
- infuse for 24 hours in 1 litre of water
- Strain and spray
- Strong deterrent effect
- Use every 3 days
Nettle decoction:
- 100g fresh nettles
- soak in 1 litre of water for 24 hours
- Ferment v