Biocontrol, or biological control, might sounds like scary science fiction, but quite the opposite is true. It’s not science fiction, it’s just good science! Biocontrol relies on the use of living organisms to help manage damaging pest populations. In effect, it uses nature’s best defenses to protect against insect invaders that harm trees and shrubs.
Biocontrol uses natural enemies as a form of treatment. Natural enemies are organisms that kill, decrease the reproductive potential of, or otherwise reduce the numbers of another organism. Predators, parasitoids, and pathogens are all natural enemy groups that could be included in landscape biocontrol efforts as part of a comprehensive plant health care program.
Introducing New Species to Manage Exotic Pests
Classical biological control focuses on the management of exotic pests. When pests are introduced to a new geography, they often leave behind naturally occurring enemies. These enemies would have otherwise kept the pest in check in their native range, but are no longer present. Researchers sometimes identify the natural enemies from the pest’s home range and introduce them into the new area to assist with control. Some intentional introductions have been successful while others have resulted in further negative environmental side effects.
Increasing Populations of Existing Beneficial Organisms
When natural enemies of a certain pest are already present in an area, releasing additional ‘enemies’ can be highly effective in pest management. This is called augmentation biological control. Some common examples include the release of lacewing larvae, lady beetles and predatory mites, which are known to provide pest suppression.
For this method to be effective, in-depth knowledge of the pest and its natural enemies is paramount. There must be an understanding of which enemy is appropriate for a given pest and environment. Careful monitoring of a landscape helps ensure natural enemies are released at an appropriate and effective time. Sometimes, repeatedly introducing small numbers of a natural enemy is better to boost pest regulation throughout the season. Alternatively, releasing a large number at one time may rapidly reduce a pest outbreak.
Creating Habitats that are Favorable for Natural Enemies
While releasing natural enemies into a habitat provides additional control, it’s important to remember that these insects already exist within a landscape! Unfortunately, suburban landscapes may not be as conducive to these beneficial organisms. Conservation biological control seeks to preserve these insects and naturally encourage population growth. When natural enemies thrive, they are better able to continuously regulate pest populations.
The conservation of natural enemies involves adopting practices that support their existence while avoiding practices that would be considered harmful. Diverse landscapes that have a variety of flowering resources and vegetation layers that include ground cover, shrubs, understory and overstory trees are more likely to support a wider range of natural enemies. Other treatments used in the landscape should also be considered. Selective products targeted at specific pests should be used in place of those that are broad-spectrum.
Biocontrol and Integrated Pest Management
Biological control is one tool within an Integrated Pest Management (IPM) program for managing insects and diseases that impact woody plants. This type of sustainable care typically involves more than biocontrol. Practices including proper irrigation and mulching as well as the responsible use of other treatments are also important. This approach is a joint effort where an arborist works closely with the property owner so that problems can be identified early and treatments timed appropriately.
