How to effectively combat thrips?

Thrips are among the most common and feared pests in indoor growing. Tiny and inconspicuous, they attack leaves by sucking the sap, leaving silvery spots, brown scars, and general weakening of the plant. If left untreated, an infestation can quickly spiral out of control.

To better combat them, it is essential to understand their life cycle , because each stage requires a specific approach.

The life cycle of thrips

Thrips go through several stages of development:

• Egg : Laid directly into leaf tissue. Invisible to the naked eye, protected within the plant.
• Larvae (stages I and II): active on the underside of leaves. They cause the majority of damage by feeding on the sap.
• Nymphs (pre-nymph and nymph): fall to the ground and take refuge in the substrate or plant debris to transform. They do not feed at this stage.
• Adults : Mobile, capable of flying and dispersing quickly throughout the crop. They reproduce quickly and lay new eggs.

A complete cycle can last as little as 2 to 3 weeks depending on the temperature, which explains the speed of infestations.

How to act according to the stages of development

1. Eggs (in leaves)

• Possible action : difficult to eliminate directly. Action is mainly taken in prevention and by limiting the reproduction of adults.
• Strategies : maintain good humidity (thrips prefer dry air), isolate affected plants, monitor with yellow or blue sticky pads.

2. Larvae (on leaves)

• Key action : This is the most destructive stage, and therefore the priority for treatment.
• Effective methods :
  • Clean the leaves regularly (shower, damp cloth, black soap, neem oil, alcohol).
  • Introduce predatory auxiliaries such as Chrysop or Neoseiulus Cucumeris , very effective against young larvae.
  • Apply an insecticide suitable for indoor crops if necessary (not compatible with predatory insects, you risk killing them too).

3. Nymphs (in the substrate)

• Key action : don't forget them, otherwise the population will constantly regenerate.
• Effective methods :
  • Cover the substrate with a thin layer of sand or perlite to hinder transformation.
  • Use nematodes ( Steinernema feltiae ) to be watered into the substrate: they target the nymphs directly.
  • Maintain strict hygiene: remove dead leaves, limit plant debris.

4. Adults (mobile and reproductive)

• Key action : limit dispersal and reduce reproduction.
• Effective methods :
  • Set up yellow/blue sticky traps to capture flying adults.
  • Properly ventilate the growing space to disrupt their flight.
  • In case of severe attack, apply a targeted treatment (neem oil, black soap, insecticide).

Conclusion: Combine approaches to win the battle

Fighting thrips requires a comprehensive and ongoing strategy :

• Trap and eliminate adults, don't hesitate to crush them with your fingers if you see any!
• Clean and treat leaves regularly to target larvae,
• Act in the substrate against nymphs,
• Reinforce prevention through good cultural practices (controlled humidity, isolated plants, strict hygiene, cleaning damaged leaves).

By combining mechanical, biological and natural methods , you create an environment unfavorable to thrips and effectively protect your plants.

For biological control, there are many choices than the Rootsum site.