If we want to establish predators or parasitoids early-on, before pests are present, we need to give them something for dinner. If we serve them the right type of food, the predators not only survive, but reproduce and build populations in the absence of the pest.
An excellent way to get beneficials started is to offer them food on “banker plants”. A “banker plant system” is a rearing / release system consisting of three basic elements:
- The banker plant.
- Alternative prey or other food to sustain natural enemies.
- The natural enemies themselves.
When using alternative prey, it is important to use plants which harbor prey that is not a potential pest of the protected crop, nor a breeding pool for hyperparasitoids. The most commonly known banker plants are cereal plants with aphids that are widely used to introduce aphid parasitoids. However, these banker plants can have the drawback that they might support hyperparasitoids, which attack the aphid parasitoids.
Flower power
These pitfalls can be avoided if we use banker plants that cater to the vegetarian side of our predators and parasitoids. The diet of many predators and parasitoids is not restricted to prey alone. Often they require flowers which provide them with nectar or pollen, while some others feed on plant sap. Predatory bugs, like Orius, are especially dependent on pollen and nectar for peak performance. For these beneficials “flowering banker plants” could be an effective banker system.
At Biobest we have many years of experience using flowering “black pearl” pepper plants to support establishment of Orius in ornamentals. As we are strong believers in the use of banker plant systems as a tool to support biological control, our R&D department conducted a range of trials to further optimize this system. The trials consisted of a broad screening of 14 different flowering plant species or plant varieties to identify the most effective banker plants to help establish the flower bug Orius laevigatus. The flowering plants were tested both in terms of their attractiveness for Orius, and with regard to their suitability in supporting Orius reproduction.
Small plant, big impact
While some plants were found to be completely unsuitable, others supported a 15-fold increase of the Orius population in absence of prey over a period of a mere two weeks. On the basis of these trials we were able to select two Capsicum varieties that are even more effective than the “black pearl” variety. Also the small, but long-flowering “sweet Alyssum” (Lobularia maritima) was shown to have particular potential, as this plant was shown to be very attractive to Orius and supported predator reproduction over several weeks.
Initial field trials in strawberries yielded very promising results, showing better Orius establishment and a reduction in thrips levels in plots with Alyssum as compared to control plots.
In the upcoming season, Biobest will take this novel concept to trials at the commercial scale. This way growers will be able to see for themselves that “flowering banker plants” not only brighten-up the greenhouse, but more importantly, that they are a low maintenance, practical and effective tool to help control problem pests.