Banker plants are a method used in agricultural and horticultural settings to manage pest insects. These non-crop plants are grown specifically to support populations of beneficial insects, also known as biological control agents. The beneficial insects reproduce and thrive on these banker plants, creating a consistent supply of natural enemies that can move to the main crop and control target pests. This approach provides a proactive, living defense system for sustainable pest management.
How Banker Plants Function
Banker plant systems operate on a principle of indirect pest control by providing a reliable food source or habitat for beneficial insects. The banker plant hosts a non-pest prey species, such as an aphid that does not feed on the main crop. This alternative prey allows beneficial insects, like parasitic wasps or predatory mites, to establish and reproduce their populations.
As the beneficial insect population grows on the banker plants, a “bank” of natural enemies is created. When target pests appear on the main crop, these established beneficial insects disperse from the banker plants to control the pest population. This continuous presence of natural enemies helps keep pest numbers below damaging levels.
Advantages of Employing Banker Plants
Employing banker plants offers several benefits for pest management in agricultural and horticultural environments. A primary advantage is the reduced reliance on chemical pesticides, which contributes to environmental sustainability and minimizes the development of pesticide resistance in pest populations.
Banker plants promote biodiversity by fostering a stable presence of beneficial insects within the growing area. They provide long-term, stable pest control by ensuring a continuous supply of natural enemies. This can also lead to cost savings over time and integrate well into comprehensive integrated pest management (IPM) strategies.
Common Banker Plant Applications
A widely recognized banker plant system involves using cereal grasses, such as barley or oats, to host the bird cherry-oat aphid (Rhopalosiphum padi). This aphid species feeds on monocot plants like grasses and does not pose a threat to most dicot cash crops.
The bird cherry-oat aphid serves as an alternative food source for beneficial parasitoids, such as Aphidius colemani wasps. These wasps lay their eggs inside the aphids, and as the wasp larvae develop, they parasitize and kill the aphids. Once established, Aphidius colemani can effectively move from the cereal banker plants to the main crop to control common pest aphids. Another application involves using ornamental pepper varieties to support predatory mites like Amblyseius swirskii. These mites feed on pollen from the pepper plants and effectively control pests such as silverleaf whiteflies and thrips on various greenhouse crops.
Establishing Banker Plant Systems
Establishing banker plant systems involves careful selection and placement to ensure their effectiveness. Growers need to choose banker plant species that are suitable hosts for the desired beneficial insects and their non-pest prey. For instance, wheat and barley are more effective than oats for supporting populations of bird cherry-oat aphids and Aphidius colemani wasps.
Proper placement of banker plants is also important; they can be situated within greenhouses, along field edges, or in pots. For systems utilizing predatory mites, ensuring that the banker plant foliage overlaps or touches the main crop can facilitate the mites’ movement. Timing of planting is also important, as banker plants should be introduced proactively before pest populations are expected to appear, to allow beneficial insect populations to establish. Consistent watering and fertilization are necessary to ensure the banker plants thrive and continue to support healthy beneficial populations.