Using Biocontrol in High Tunnels or Greenhouses
Using "banker plants" to help beneficials reproduce is a great option to reduce costs of using biocontrol.
Biological control of pests can be very effective in greenhouses or high tunnels, but it requires a great deal of commitment. It is an option for a variety of reasons, whether your operation is organic, there is consumer demand, pesticides cannot be applied, or due to pesticide resistance issues. Often, there is interest because someone else raves about its success. Anyone can use biocontrol. A primary hurdle is using biocontrol without taking a hit on profits. Using biocontrol requires preparation, practice, and patience.
Switching to biocontrol requires full commitment with complete understanding and ability to adapt.
- Know the biology, life cycle, and behavior of your common pests and the biological control agents that target them and are compatible with the crop and greenhouse conditions.
- Beneficial nematodes are microscopic roundworms that enter the host insect through natural openings, and produce protein-destroying enzymes on pests such as thrips and fungus gnats.
- Predators, such as lady beetles, lacewings, minute pirate bugs, and predatory mites, seek out insect and mite prey, and are usually generalists, feeding on a variety of pests.
- Parasitoids are wasps or flies that lay eggs and complete their life cycle, from larvae to adult, inside or on their host. A range of species are commercially available that target aphids, whiteflies, and scale insects.
- Get to know the biocontrol suppliers and their shipping process. Select reliable suppliers with whom to work.
- Spend at lease one season transitioning to softer pesticides.
- Biologicals and pesticides don’t mix. Direct contact or residues from prior applications can kill some species. Some biorationals (insecticidal soap, hort. oil, Bt, etc.) may be used when absolutely necessary.
- Before introducing biocontrol, take measures to lower the existing pest populations to increase the chances for success.
Begin by focusing on a single pest and a single natural enemy. Longer term crops such as perennials or poinsettia that are not moved around extensively are easier to manage with biocontrol. Once you are comfortable with biocontrol of the first pest, gradually ramp up to a full program.
Keep in mind that a quality biocontrol agent and reliable supplier are key to establishing a successful program. In the beginning, work with the supplier to determine the optimal release schedule for the organisms you are using. Request that orders are shipped overnight, if possible. Once they arrive, inspect the contents carefully before release. If the numbers are low or the insects are dead, a good quality supplier will provide reimbursement or a replacement shipment.
Using biocontrol successfully is impossible without a reliable scouting program. Train yourself and your employees to “always be scouting” rather than having a single person monitoring just once per week. Biological control works best when pest populations are kept at low numbers, and should not be relied upon after a flare up occurs.
When it comes time to sell or distribute your plants, you may find that they are harboring a population of beneficials. As much as we don’t like to hear it, some customers will not tolerate any insects, whether they are a pest or not. In this case, the crop can be sprayed outside the greenhouse, before it goes out, to prevent any complaints.
A successful biocontrol program will rely on regularly scheduled releases of beneficials throughout the growing season of the crop, and only when pest populations are moderate to low. After releasing beneficials, it may take several weeks to see noticeable reductions in pest levels. If pest densities get too high, the supplier you work with can help identify compatible pesticide options.
Initially, the cost of managing pests with biocontrol is greater than using conventional pesticides. For some growers, the financial commitment is worth it to get a premium on their product, and for avoiding sprays and dealing with re-entry intervals. Some growers report that finding labor is easier when they know they don’t have to spray.
Biocontrol is a growing trend in the greenhouse industry and beyond, and it can be successful with the right preparation, expectations, and under the right conditions. As your operation learns more about implementing biological control, efficiency will be increased and costs reduced.
- Marion Murray, IPM Project Leader
For Additional Information:
bioworksbiocontrol.com/nov2010.pdf: An article describing the larger producers of biocontrol agents.
Greenhouse Biocontrol Workbook, Cornell University: nysipm.cornell.edu/nursery_ghouse.pdf
Greenhouse Biocontrol Handbook, Penn State University: pubs.cas.psu.edu/FreePubs/pdfs/agrs96.pdf