Biological Control Methods
The methods of biological control pest management are divided into three categories: introduction (aka classical), augmentation, and conservation. Simply put, biological control uses living natural enemies - predators, parasitoids and pathogens - to manage pest populations.
Natural Enemies are organisms that prey upon or parasitize insect, mite, plant disease, weed and vertebrate pests in agricultural or managed landscape settings. Natural enemies have a variety of common names including, but not limited to, beneficials, beneficial organisms, good bugs and biological control agents or biocontrol agents (= BCAs). As their name suggests, they are naturally occurring organisms that help maintain ecological balance through predator-prey interactions. The concept of natural enemies and using them for pest control has been understood for millennia, but the first use of the term, natural enemies, to describe these organisms has not been determined. Harry Scott Smith is credited with being the first to use the term biological control (the use of natural enemies for pest control) back in 1919.
Introduction
Introduction is the process of safely introducing a small population of a natural enemy to restore ecological balance to a system overwhelmed by populations of a non-native pest species.
Introduction involves foreign exploration and is a method reserved for research scientists associated with a university or the USDA who have access to a federally approved quarantine facility. Groups of highly trained experts are assembled for an introduction program, and such programs are initiated when there is an accident. The accident being the unintentional movement of a species into an area where they previously did not occur. Such an accident is often referred to as an invasion. Invasive species are considered one of the top threats to agricultural production in California, as well as its natural and urban environments.
When an organism gets introduced to a new area, there are several possible fates. The one most feared is that a population will establish, successfully feed and breed on an important crop, and its numbers grow wildly out of control. This nightmare scenario happens all too frequently. Recent examples in California include Asian citrus psyllid, Olive psyllid, shot hole borers, and the dotted paropsine leaf beetle. And its not just insects. There are invasive plants and plant pathogenic diseases as well.
The goal of introduction biological control is to send scientists to the invasive organism's native home to locate populations and determine if those populations are naturally controlled or if they are considered pests. If the populations are in balance and are controlled naturally, the next step is to identify the organism responsible for this control and bring it back to a quarantine facility in the US for further study.
Intensive research is conducted in quarantine to determine if the natural enemy is suitable for release. If it is, a federal permit is acquired, and an introduction is conducted to target the invasive pest, as shown in the photo. This is the “introduction” phase of this biological control method. It's how the first project was conducted in 1888, which is why it's also called “classical” biological control.
This method recreates the ecological balance observed in the native home in the newly invaded area, thus avoiding the need for chemical or other costly control methods.
Introduction biological control differs from augmentation and conservation in that it focuses on just one new natural enemy species to manage one invasive pest species.
Augmentation
Augmentation means manually adding more of a natural enemy species into the environment at the appropriate time and place to improve pest control results. Natural enemies used for augmentation are either already established by way of an introduction program or they are native, naturally occurring species. Augmentation differs from introduction because it uses natural enemies that are present in the environment, This method is employed when the existing natural enemies are not able to provide the level of pest control needed for successful plant growth due to varying biological or environmental factors.
The practice of augmentation is available for everyone to use, not just researchers. The key is to use the natural enemy best suited for the pest problem and ensure you have the correct quantity. Augmentation also allows you to manage multiple pest/natural enemy interactions concurrently. How do you know which natural enemy is best? Seek professional guidance from experts working for a natural enemy supplier. Commercial growers consult with licensed pest control advisors or certified crop advisors. Where does one get natural enemies? Natural enemy suppliers produce a few to several different species of natural enemies and sell them. Some regions have a grower cooperative that provides natural enemies and pest control advice to their members.
There are roughly a dozen commercial insectaries in the US and many more in countries around the world. Koppert, Inc. is an international company that employs skilled technicians in the US to advise growers on how to use natural enemies in the field. They have also developed a Side Effects app to help users understand the impacts of pesticides on beneficial organisms and pollinators. Bugs for Bugs in Queensland, Australia, is a full service insectary that provides growers technical assistance in deploying and assessing natural enemy effectiveness. Arbico Organics is a commercial insectary that provides advice and quantities of natural enemies more suitable for homeowners or small property managers. For a comprehensive listing of companies that produce beneficial insects, visit The Association of Natural Biological Control Producers.
The grower cooperative type of insectary is unique, and only one remains in business at the time of this writing - Associates Insectary, Inc. in Santa Paula, California. Read more on the history of the grower cooperative model Fillmore Citrus Protective District.
Conservation
This type of conservation is all about conserving one type of resource - natural enemies - and it’s a method anyone can adopt.
Conservation biological control has two approaches:
substituting broad spectrum insecticides with selective chemicals
enhancing the landscape to provide food, shelter, and water to improve natural enemy activity in cropping fields.
The conservation method considers the cropping system as a whole, with all of the interconnected flora, fauna and the larger environment, which is very different than the previous two methods. With the many variables involved, it’s difficult to develop predictable outcomes that we’ve come to expect with other pest control techniques, like insecticides. It’s difficult to conduct research on conservation biological control and publish results that provide recommendations with consistent outcomes; the “data-based recommendations”. Data-based recommendations are trustworthy and have become the industry standard, and trust is needed to achieve widespread adoption and implementation.
On the chemical side of natural enemy conservation, the goal is to reduce the hazards that chemical applications pose to natural enemies present in the system. Since natural enemies reduce pest populations, for free, let’s not do anything to impede or harm them. In years past, the focus was on reducing the use of broad spectrum pesticides - the chemicals that indiscriminately kill any kind of insect they contact. From the 1960s through the 1980s, there were few pesticide categories registered for use in cropping systems, so reducing the use of these chemicals was challenging. Since the 1990s, there have been a considerable number of new chemical classes of pesticides that are more selective in their targets, thus limiting their negative impact on natural enemies. However, even the new selective pesticides are not free of negative impacts. The article Various Novel Insecticides Are Less Toxic to Humans, More Specific to Key Pests offers a sobering example.
Enhancing the landscape, or otherwise manipulating the environment, to aid natural enemies is a complex undertaking. It requires experimentation and commitment by the user to be successful. One federal agency, Appropriate Technology Transfer for Rural Areas (ATTRA), has produced several reliable and user-friendly references to guide biological control enhancement in agriculture cropping systems. ATTRA was developed and is managed by the National Center for Appropriate Technology (NCAT).
Visit the Biological Control Resources page for publications on conservation biological control.