Using Banker Plants

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"You Can Bank On It: Banker plants can be used to rear natural enemies to help control greenhouse pests." PDF File

          Biological control is only one tool in our pest-management arsenal.  Its success depends on the other tools that will be used and the availability of beneficial organisms.  Spider mite control using anyone of the many available natural enemies will only work if the foundation of the program has been established. The foundation consists of methods to prevent, detect and manage the major pests. In certain notable cases, there are good and effective natural enemies for the secondary pests.  However, experience has shown that reliance on too many natural enemies is complicated and slowly adapted if it is adapted.

          Growers move to biological controls for many reasons but a crisis is often the motivation for many of those that have been successful.  The crisis is often the loss of effective chemical controls and this usually is for one primary pest; mites, whiteflies, leafminers.... As a result, the biological control agents are often forced into existing pest management programs. In the past, many of the pesticides used precluded integration of these tactics. New chemistry and in some cases new natural enemies make this less of an obstacle.


Prepare the Foundation:

        Establish a scouting program

        Prepare a detailed list of all potential pests and methods for management.

        Prepare a list of chemicals safe to use on the crop.

        Prepare a subset of these chemicals that are relatively safe to the beneficials you intend on using.

        Find reliable sources for the beneficial organisms and other materials needed.

        A reliable source for guidance is also extremely useful.

           Once the foundation is established, the implementation of your plan can begin. Because the establishment phase is the most critical and often the most difficult, my laboratory have concentrated on the development of techniques that will help in this phase. 


        Provide natural enemies not commercially  available.

        Provide growers with methods they can use to evaluate the quality of purchased beneficials.

        Increase the probability of establishment

        Make the use of biological control more economical and reliable.

        Allows greater flexibility in the use of pesticides because the banker plant can be removed or protected during pesticide application. 

What is a 'BANKER ' Plant or Open Rearing System?

 A banker plant is a plant that has a population of reproducing natural enemies (NE) on  it. This terminology is restrictive and does not allow for the sachets used to produce N. cucumeris or the bucket rearing system used to produce parasitoids and predatorss of measlybugs.

 There are 2 types of banker plant systems.

          One system uses the same pest species or crop pest (CP) as the one that is to be managed. This system obviously posses a significant risk.

          The second system uses  a fictitious, surrogate or alternate host or prey (AH).

This host or AH is reared on plants that aren't grown as a crop in the greenhouse where they will be used. They should have a limited host range which does not include the plants being grown commercially.

         CROP=plants we are trying to protect.

Examples: ornamentals, tomato, pepper, cucumber, or herbs.

         CP=crop pest. The organism that is the focus of our management program.

Examples: two-spotted spider mite, melon aphid, silverleaf whitefly.

         AH=alternate host. This is an organism that will not feed on the crop but on another easily grown plant that is of no economic value and would otherwise not be found in proximity to the crop. The AH is also an organism on which our natural enemies will feed and reproduce.

Examples: Bird-cherry aphid (Rhopalosiphum padi), greenbug (Schizaphis graminum), corn-leaf aphid (Rhopalosiphum maidis), Papaya whitefly (Trialeurodes variabilis [Quaintance]) or Banks grass mite (Oligonychus pratensis [Banks]).

        BP=banker plant. This is the banker plant described above and the plant on which we intend to rear the AH.

Examples: winter barley or wheat, sorghum, corn, or papaya.

         NE=natural enemy. This is the natural enemy or organism that will feed on both the crop pest (CP) and the alternate host (AH).

Examples: Encarsia transvena, Aphidus colemani, Stethorus spp., Feltiella acarisuga, Scolothrips sexmaculatus, Galendromus occidentalis, Neoseiulus californicus, or Phytoseiulus persimilis.




This is a schematic view of the crop being attacked by the pest we would like to control.  Examples would be poinsettia infested with silverleaf whitefly (Bemisia argentifolii) or ivy infested with two-spotted spider mite (Tetranychus urticae).



This is a schematic view of natural enemies being released on the crop to protect if from the pest of interest.



This is a schematic view of the banker plant (BP) being attacked by the alternate host (AH).  Examples would be papaya infested with papaya whitefly (Trialeurodes variabilis [Quaintance]), corn infested with Banks grass mite (Oligonychus pratensis [Banks]) or sorghum infested with corn leaf aphid (Rhopalosiphum maidis). 



This is a schematic view of natural enemies being released on the banker plant to attack the alternate host and increase in numbers. 



This is a schematic view to show that the alternate host does not infest the crop.


 This is a schematic view of natural enemies moving between the crop and the banker plant.  This is the aim of the system: the natural enemies will move from the banker plant in search of food.  If the crop is infested with the pest for which the system was designed (spider mites or whiteflies), they will be attacked and killed.



Banker plants in interspersed throughout the crop establishing a resident population of natural enemies that will attack the crop pests if they should happen to try infesting the crop.



Examples of Systems: 


Papaya whitefly (Trialeurodes variabilis [Quaintance]) and Encarsia sophia. This species was previously called Encarsia transvena.

(clicks on photo to enlarge)


Encarsia sophia

Papaya whitefly


The two on the left were killed by an adult E. sophia feeding on them



Banks grass mite (Oligonychus pratensis [Banks]) and various mite predators: Stethorus spp., Feltiella acarisuga, Scolothrips sexmaculatus, Galendromus occidentalis, Neoseiulus californicus, or Phytoseiulus persimilis.

The following video clip is from a DVD developed by IPM Florida and produced by IFAS Communication Services. The authors of the DVD are Drs. Jennifer L. Gillett & Norman C. Leppla. The title of the DVD is Integrated Pest Management in Florida and contains a number of clips that highlight successful IPM projects in Florida.

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Rhopalosiphum padi (Bird-cherry aphids) on winter barley (Hordeum vulgare L.) Schizaphis graminum on winter wheat or Rhopalosiphum maidis (Corn leaf aphid) on sorghum.  All of these aphids can serve as prey for various predators and parasitoids that attack melon and green peach aphids.