Biological control agents have proven very effective in managing several pests in high tunnels and greenhouses; however, some of the challenges include the cost of purchasing biological control agents and keeping those parasitoids and predators in the structure.
Consider using banker plant systems as part of your biological control plan. A banker plant system supplies a non-pest prey for parasitoids and predators to use as an alternative food source. The plants housing the non-pest prey also provides a home for beneficial insects promoting reproduction; thus, providing the next generation of pest assassins. This relationship reduces the need to purchase fresh natural enemies.
Producing banker plants to help maintain this parasite includes growing cereal grains in a pot (or hanging basket) and introducing cereal aphids to create a population high enough to sustain the parasite population. The plants will continue to produce more parasitoids, but when the cereal aphid population is low, fresh banker plants will be needed to replace the previous ones.
The most common banker plant system is one that uses a non-pest aphid species, cereal aphid (bird cherry oat aphid, Rhopalosiphum padi), that lives and feeds exclusively on cereal plants. This system is often used in greenhouses to help maintain the parasite ( Aphidius colemani) which is used to manage aphid pest species.
The recommendation is to start with two banker plants per greenhouse and to add one each week. It is critical to remember to continue producing new banker plants to add throughout the season. Banker plants should be added as soon as plants are introduced. Waiting until you see your first aphid pest is too late, as it can take three to four weeks before new adult parasites will be produced.
West Virginia State University started producing banker plants in the spring of 2017 and found them easy to create. It was also found that with the use of banker plants, our parasitoids and predators were maintained for a longer duration of time. Banker plants will continue to be added this year as part of the integrated pest management (IPM) program to support and extend purchased biological control agents.
Barbara Liedl, WVSU Extension Plant Breeding and Genetics
Last Reviewed: April 2018