Aphid Banker plants

Description: Banker plants are plants that are different from the primary crop being grown. They assist in establishing, supporting and maintaining a population of one or more biological control agents that are released on the banker plants. Banker plants support the biological control agents with pollen or other plant material, or a host pest that doesn’t affect the primary crop grown.

Use in Biological Control: The aphid banker plant system is an open rearing system. For it to be most effective, the banker plants need to be introduced as early in the crop as possible before aphids appear. The system is based on introducing cereal aphids into a greenhouse on cereal plants (i.e., rye, barley, wheat). Cereal aphids only reproduce on monocotyledonous plants. Cereal aphids serve as a food source for the parasitic wasp Aphidius colemani, which reproduces on the cereal aphids.

Another benefit of the aphid  banker plant system is the plants attract outside naturally occurring aphid predators such as lady bugs, lace wings, syrphid flies and gall midges — especially during the spring. These predators are attracted by the aphids on the banker plants, even if there are no aphid pests present on the greenhouse crops. In traditional pest management programs, these naturally occurring predators would not survive pesticide applications.

For Best Results: Start the aphid banker plant system as early as possible in the crop cycle. Once the first banker plants are out in the greenhouse and inoculated with A. colemani, it takes another four weeks for the wasps to become reproductive. Introduce a minimum of one banker plant per acre per week or two every other week. The system is only successful when new banker plants are brought into the greenhouse. This supports continuous production of A. colemani, instead of having peaks and valleys in the number of wasps produced in the crop.

Having more banker plants doesn’t hurt. Many growers use higher rates, especially in April to ensure a high population of Aphidius in May when aphids are very active. Do not remove older banker plants until they start to die off. Rye and barley plants can last for eight to 10 weeks. Monitor the banker plants and make sure they are watered. Drip irrigation works the best rather than overhead watering.