How to control thrips biologically

Thrips (Thysanoptera), particularly Frankliniella occidentalis and Thrips tabaci, are among the most persistent pests in horticultural crops and greenhouses. Their accelerated life cycle, ranging from 5 to 20 days depending on temperature, and their high dispersal capacity make control a constant challenge for any grower.

If you have already tried conventional insecticides and the results were below expectations, you are not alone. Resistance accumulated over decades has rendered many chemical solutions ineffective against thrips. The good news? Biological control now offers consistent and sustainable results, combining active monitoring, chromotropic traps, biological insecticides, beneficial organisms and good cultural practices.

In this article, we explain how to control thrips step by step, using tools and strategies that work in the field.

Identification and damage caused by thrips

Before controlling thrips, it is essential to recognize them and understand their behaviour. These insects scrape plant tissues and suck out cellular contents, causing damage that begins subtly but worsens quickly.

The most common signs include leaf silvering, deformation of shoots, necrosis of young tissues, general reduction in plant vigour and bronze spots on flowers and fruits. But the most serious damage is invisible: thrips are vectors of devastating viruses such as TSWV, INSV, IYSV, GRSV, TCSV and CaCV, which can compromise entire crops with no possibility of recovery.

Under favourable conditions, with temperatures between 25 and 30 °C, populations can multiply up to tenfold in just two weeks. This is why early detection is so important: when visible damage appears, the infestation is already advanced.

Effective biological strategies to control thrips

The biological approach does not rely on a single product. It is an integrated system of tools that, together, keep thrips populations below the economic damage threshold.

Chromotropic traps and semiochemicals

Blue chromotropic traps are the first line of defence. They serve three simultaneous functions: monitoring populations and assessing pest pressure, detecting early hotspots before damage becomes visible, and reducing the number of flying adults.

Studies in greenhouses under moderate pressure show captures between 150 and 300 thrips per trap per week, providing a clear picture of infestation dynamics. For a small greenhouse, 1 to 2 traps are sufficient for monitoring. In larger crops, the recommendation is 2 to 10 traps per hectare, evenly distributed.

Biological and botanical insecticides

Biological insecticides are essential to reduce populations without generating resistance, the Achilles heel of conventional chemical treatments. Each type of product acts through different mechanisms, allowing effective rotation.

Beauveria bassiana is particularly effective against young larvae: studies show that populations in plants treated with this fungus are up to 70% lower than those in untreated plants, with mortality peaks of 64.8% eight days after application.

Metarhizium anisopliae works under different conditions, although performance is better above 20 °C. It is a complementary option that allows rotation of active substances and prevents the pest from developing tolerance.

The nematodes Steinernema feltiae are applied to the soil, where they attack the pupal stages of thrips that complete their cycle in the substrate.

Cultural management

Good cultural practices do not replace treatments, but they enhance their effectiveness and reduce pest pressure before numbers increase. The most important measures include: removing plant debris that serves as shelter, reducing excessive humidity near the soil, eliminating spontaneous host plants at crop margins, maintaining adequate ventilation in greenhouses, and avoiding nitrogen‑rich fertilization, which promotes softer tissues that are more attractive to thrips.

The role of beneficials in thrips control

Beneficials are organisms, predators or parasites, that feed on pests and contribute to the biological balance of the crop. In the case of thrips, three species stand out for their proven effectiveness.

The great advantage of beneficials is that their action is continuous and compatible with biological insecticides, provided that the substances are selected carefully. This integration increases overall efficacy and reduces the risk of resistance.

Recommended integrated programme

Combining monitoring, biological treatments and cultural management in a structured programme is what ensures consistent results throughout the season. An integrated programme to control thrips includes six key steps:

• Install chromotropic traps: 1 to 2 per small greenhouse, 2 to 10 per hectare in larger crops
• Monitor weekly: record trap captures and inspect visible plant damage
• Apply biological insecticides preventively: start before population peaks, not after
• Reinforce applications during peaks: increase frequency when trap captures rise
• Integrate beneficials when possible: release predators as a complement to biological treatments
• Rotate active substances: alternate between Beauveria bassiana, Metarhizium anisopliae and nematodes to avoid tolerance

The key is prevention. When intervention begins before thrips multiply exponentially, pressure remains manageable with biological tools, without the need to resort to chemicals.

Advantages of biological control of thrips

Choosing biological control is not just an environmental decision. It has a direct impact on production quality and business sustainability.

• Reduces resistance: rotating between organisms and biological substances prevents thrips from developing tolerance, a chronic problem with chemical insecticides

• Protects natural beneficials: unlike broad‑spectrum chemicals, biological products preserve the predators and parasites already present in the crop

• Improves final quality: fruits and vegetables free from chemical residues have higher commercial value and market acceptance

• Suitable for organic farming: all products and methods described are compatible with organic production regulations

• Sustainable and safe for the operator: no toxicological risks for the applicator and no impact on the surrounding ecosystem

Biological control of thrips is the most effective and sustainable strategy currently available. Combining chromotropic traps for monitoring and capture, biological insecticides such as Beauveria bassiana and Metarhizium anisopliae, predatory beneficials and good cultural practices keeps populations below the economic damage threshold, season after season.

At Biosani, you will find chromotropic traps, biological insecticides and all the resources needed to implement a biological thrips control programme tailored to your crop. Consult our product catalogue or contact us for personalised advice.