What Are Banker Plants?

Banker plants are companion plants grown in or around crops to support populations of beneficial insects. Instead of applying predators or parasitoids repeatedly, banker plants provide food and habitat that keeps these natural enemies alive and working even when target pest populations are low.

In greenhouses, they help maintain a steady presence of biocontrol agents, so they’re ready to act when a pest outbreak begins.

Why Use Banker Plants in Greenhouses?

• Keeps beneficials active without constant reintroduction
• Provides early intervention, pests are controlled before they spread
• Reduces costs over time by lowering the number of releases needed

Common Banker Plant Systems & What They Support

Aphid Banker Plant
What it supports: Aphidius colemani Plant used: Wheat, barley, or oat How it works: These grasses host a harmless grain aphid (Rhopalosiphum padi), which feeds on the plant but doesn't damage your crops. Aphidius colemani, a parasitic wasp, uses these aphids to reproduce, ensuring it stays active and ready to target pest aphids like Myzus persicae or Aphis gossypii when they appear.
Purple Flash Ornamental Pepper
What it supports: Orius insidiosus (minute pirate bug) Plant traits: Compact, attractive, with pollen-rich flowers How it works: Orius feeds on thrips, aphids, and small insects — but it also uses pollen to survive when prey is scarce. Purple Flash produces abundant pollen, making it an excellent banker plant to keep Orius populations stable in ornamental and vegetable crops.
Mullein (Verbascum spp.)
What it supports: Dicyphus hesperus (mirid bug) Plant traits: Tall, broad-leafed, fuzzy texture How it works: Dicyphus is a generalist predator used for whiteflies, aphids, and thrips. It thrives on mullein, where it can shelter, lay eggs, and even feed on the plant if prey is limited. Mullein is especially useful in long-cycle crops like tomatoes.
Alyssum (Lobularia maritima)
What it supports: Orius insidiosus & hoverflies Plant traits: Low-growing, white or purple flowers, blooms continuously How it works: Alyssum provides nectar and pollen, which are key energy sources for many natural enemies. It helps Orius and pollinators like hoverflies persist in greenhouses while improving biodiversity and beneficial insect activity.

 

How to Set Up a Banker Plant System in Your Greenhouse

Step 1: Choose the Right Banker Plant

• Identify your main pest targets (aphids, thrips, whiteflies)
• Match with the natural enemy you plan to support
• Select a compatible banker plant (e.g., wheat for aphids, Purple Flash for thrips)

Step 2: Pot and Grow Your Banker Plant

• Use clean, pest-free soil in pots or trays
• Grow in the same environment as your crops (lighting, humidity, etc.)
• Start early, so the plant is established before pest pressure rises

Step 3: Introduce the Beneficial Insect

• Release your beneficial directly onto the banker plant.
• To support establishment, consider adding a supplemental food source like Bugfeed, which provides the protein and nutrients many natural enemies need to thrive.
• For aphid banker system, start by pre-inoculating the banker plant with cereal aphids. You can purchase inoculated wheatgrass here. Once the aphids are established on the banker plant, introduce parasitoid wasp AphidiLiv, Aphidius colemani.
  

Monitor the banker plant regularly to ensure the population is establishing and active.

Step 4: Maintain and Monitor

• Keep plants healthy and monitor pest and beneficial populations weekly
• Replace banker plants every few weeks or as needed

 

Summary

Banker Plant	Supports	Best for
Wheat/Barley	AphidiLiv Aphidius colemani	Aphid control
Purple Flash	OriLiv Orius insidiosus	Thrips, aphids, generalist
Mullein	MiriLiv Dicyphus hesperus	Whiteflies, aphids, thrips
Alyssum	OriLiv Orius, hoverflies	General pollen/nectar support

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