Protected culture structures, such as hoophouses and greenhouses, are by nature limited in growing space. Many growers make the most of the available space by planting crops that have high returns; i.e., tomatoes, cucumbers, peppers, and eggplants. In a closed environment, it is also well worth it to put a little of the area aside for banker plants.
Any crop that provides a habitat for beneficial insects can be used as a banker plant. One of the greenhouses at Johnny’s research farm is dedicated to peppers and eggplants - both of which are susceptible to predation by aphids. In addition to the peppers and eggplants, space has been reserved for containers of oats which serve as banker plants by providing habitat for oat aphids. The oat aphids are released into the oats, which are then covered to allow the population of the pest to grow.
Why would someone release an aphid of any kind into their greenhouse and then build their population? The oat aphid is host specific to only oats; it won’t attack any other crop. At Johnny’s, once the oat aphid population has grown, Greenhouse Manager, Pam Carter, releases parasitic wasps that attack aphids of all kinds, including those that pose a danger to the peppers and eggplants. As a side benefit, the oats can also provide habitat for ladybugs, another beneficial insect and predator of aphids.
For those of you with concerns about the use of insecticides, banker plants are a practical alternative. In many cases the resulting natural controls by beneficial insects will reduce the need for insecticidal applications.