Thrips control: The complete guide

Thrips are among the most persistent cannabis pests and require a rapid response:

**Identify thrips:**

*Visual detection:*

- Tiny, slender insects (1-2mm long)

- Yellow to brown in colour

- Fast, erratic movements

- Hide on the undersides of leaves

- They fly away when disturbed

*Damage pattern:*

- Silvery, shiny spots on leaves

- Small black dots (faeces)

- Leaves turn bronze or silvery

- Severe infestation: completely discoloured leaves

- Slowing of growth

*Understanding the life cycle:*

- Egg stage: 2-7 days

- Larval stage: 5-10 days

- Pupa stage: 1-3 days

- Adult stage: 30-45 days

- Generation time: 15-30 days depending on temperature

**Immediate measures:**

*Isolate infested areas:*

- Separate affected plants from healthy ones

- Reduce air circulation between plants

- Do not share tools between plants

- Wash hands after contact

*Hang up blue traps:*

- Sticky blue traps attract thrips

- 1-2 traps per square metre

- Replace weekly

- Position: Height of the upper leaves

*Remove heavily infested leaves:*

- Cut off leaves with >50% damage

- Dispose of in plastic bag (do not compost)

- Use clean scissors

- Disinfect cut surfaces with cinnamon

**Biological control:**

*Predatory bugs (Orius):*

- Natural enemy of thrips

- Eat adult thrips and larvae

- 1-2 beneficial insects per plant

- Also have a preventative effect

- Temperature >15°C required

*Predatory mites (Amblyseius):*

- Especially against thrips larvae

- Live in the substrate and on leaves

- Long-term effect

- Can be combined with other beneficial insects

- Prefers high humidity

*Ladybird larvae:*

- Eat thrips larvae

- Particularly effective in the vegetative phase

- Favourable alternative

- Need other food when thrips are gone

**Organic sprays:**

*Neem oil solution:*

- 2-3ml neem oil per litre of water

- Add emulsifier (detergent)

- Spray in the evening (UV-sensitive)

- Repeat every 3 days

- Also treat undersides of leaves

*Soft soap spray:*

- 10-15ml soft soap per litre

- Use white potassium soap product

- Spray in the morning, rinse off in the evening

- Blocks the breathing openings of thrips

- Particularly effective against larvae

*Pyrethrin spray:*

- Natural insecticide from chrysanthemums

- Fast knockdown effect

- Short duration of action

- Apply in the evening (light-sensitive)

- Only for heavy infestations

**Systemic treatment:**

*Beneficial Bacteria:*

- Bacillus thuringiensis (Bt)

- Pour over substrate

- Bacteria are taken up by the plant

- Poison thrips when eaten

- Multiple applications necessary

*Diatomaceous earth:*

- Fine powder from fossilised algae

- Dust onto substrate surface

- Injures thrips on contact

- Use only food-grade quality

- Do not inhale

**Environmental modification:**

*Increase humidity:*

- Thrips prefer dry air

- Increase humidity to 60-70%

- Humidifier or wet towels

- Pay particular attention during the flowering phase (risk of mould)

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