The Ultimate Guide to Insect Traps

If you’re managing a greenhouse or hydroponic system, pest control is one of the most critical components of maintaining plant health and yield. One of the simplest, most cost-effective tools available to growers is the insect trap. From sticky traps to pheromone lures, these tools help control and monitor a wide range of pests—often before they become a serious problem.

Let’s take a look at how and why different traps are used, the science behind them, and how to make the most of them in your growing environment.

Why Use Insect Traps?

Traps serve two major roles in plant health management:

1. Monitoring: Detect early infestations before they escalate.
2. Control: Reduce pest populations without chemical inputs.

Used correctly, traps give you the data needed to decide whether biological, chemical, or cultural control methods are required.

Yellow Sticky Traps: The Gold Standard

The most common pest trap you’ll find is the yellow sticky trap. These are highly effective against aphids and other flying pests like whiteflies and leafminers. But why yellow?

Why Yellow?
Yellow mimics the appearance of chlorotic (unhealthy) plants—exactly what aphids are attracted to. These pests prefer weakened hosts, so yellow acts as a beacon.

What Makes Them Sticky?
Sticky traps use polybutene, an extremely adhesive compound. It’s so sticky that mishandling can lead to logistics nightmares (ask any delivery driver who’s dealt with a spill!). Polybutene is also used in mouse traps and even red and blue variants of pest traps.

Color Matters: Yellow, Blue, Black, and Red Traps

Each color attracts different pests:

• 🟡 Yellow Traps: General flying insects like aphids, whiteflies.
• 🔵 Blue Traps: Target thrips, with fewer beneficials (like parasitic wasps and lacewings) being caught.
• ⚫ Black Traps: Best for fungus gnats, though rarely manufactured due to market demand.
• 🔴 Red Traps: Often used in orchards to catch fruit flies and rosy apple aphid. Typically combined with bait like ammonium phosphate.

Some traps include synthetic pheromones to lure pests like codling moths with mating signals.

Monitoring Tips for Sticky Traps

For effective monitoring:

• Use gridded traps to count and track pest populations.
• Place traps at plant canopy level.
• Check and replace weekly.
• Record trends to decide when to deploy further control methods.

Remember: sticky traps are better suited for indoor use. Outdoors, they often attract too many non-target organisms to be practical for pest control.

Beyond Sticky Traps: Innovative and Unusual Trapping Methods

Not all traps rely on stickiness. Here are a few fascinating options:

• Spray-on traps: at Eutrema we have experimented with a polybutene spray that activated after drying. While not commercialized, it’s a concept with future potential.
• Slug hotels: In the UK, old doors are placed in fields to monitor slug populations—part of a national project known as SLIMERS.
• Wireworm monitoring: Bury toilet rolls filled with wheat to detect these soil-dwelling pests.
• Zoospore bait traps: In hydroponic systems, rotting vegetables placed in water tanks can attract waterborne oomycetes like Pythium and Phytophthora. These pathogens cause bud and root rot and are a hidden risk, especially when using untreated rainwater.

Traps and Disease Monitoring

Traps aren’t just for insects. They’re also useful for detecting zoospore-based plant diseases. If you’re battling persistent root rot, consider inspecting your irrigation system with bait traps—especially if you use rainwater or organic inputs.

Final Thoughts

Traps are an essential, eco-friendly tool for both monitoring and controlling pests in hydroponic and greenhouse systems. From yellow sticky cards to innovative bait systems, understanding how to use them strategically can prevent outbreaks, protect beneficial insects, and reduce your reliance on chemical sprays.

Article by Dr Russell Sharp

If you would like to keep up to date with subjects just like this, you can listen to both our podcasts! Links can be found bellow:

Hydroponics Daily Podcast: https://open.spotify.com/show/207T7p7fw9sPjINfSjVXW2

Cereal Killers Podcast: https://t.co/eSEbBkTVHl