Dominate Your Landscape: Use Biocontrol to Defeat Deadly Pests
by John Campanini, Technical Directors, RITree
For years, the standard response to a pest infestation was a “scorched earth” policy. If a pest was killing your trees, you sprayed a chemical cocktail to kill it—and, inadvertently, everything else in the vicinity.
But as our environmental awareness grew and chemical resistance turned “superbugs” into a reality, things changed. Looking for a more surgical solution, homeowners, scientists, and farmers began turning to nature’s “hired guns”: biological control.
What’s biological control? Biological control, or biocontrol, is the practice of using living organisms—predators, parasites, and pathogens—to manage pest populations. It’s not a new concept. In fact, it’s rather old.
Chinese citrus growers used predatory ants to defend their trees against caterpillars as early as 324 BC. Over the years, biocontrol has gained popularity, especially in tree care. Today, it’s a cornerstone of sustainable agriculture and tree care, proven time and time again.
Benefits of Biocontrol
For long-lived organisms like trees—whether in a vast forest or a suburban backyard—this approach provides unique advantages that chemical treatments can’t match:
- Long-term, self-sustaining protection
- Surgical precision (target specificity)
- High return on investment
- Reach the unreachable pests.
- Environmental and public health safety
In urban areas and parks, chemical drift poses a significant liability. Biological control removes the risk of toxic exposure to humans, pets, and local water tables. Below, we take a look at three key players in biocontrol.
Predators: Free-Living Hunters
Predators are the front-line combatants in this battle. These are the insect world’s generalists, actively hunting and consuming prey. Predators don’t just kill; they establish a presence. In a healthy ecosystem, a resident population of predators acts as a permanent security detail, keeping pest numbers below the “economic threshold” where they cause significant damage.
Two critical predators are:
- Ladybugs (Coccinellidae): Perhaps the most famous biocontrol agent, a single ladybug can consume up to 5,000 aphids in its lifetime. They are the “infantry” of the garden, providing a visible and effective defense against soft-bodied pests.
- Green Lacewings: Often called “aphid lions” in their larval stage, these voracious hunters use hooked mandibles to seize prey and inject paralyzing venom.
Other predators critical in this battle include ground beetles (Carabids), mealybug destroyers, rove beetles, minute pirate bugs, and hoverfly larvae (Syrphids).
Parasitoids: Surgical Strikes
If predators are the infantry, parasitoids are their special forces. Most parasitoids are tiny wasps or flies that have a more gruesome, yet highly effective, method of operation. A female parasitoid wasp, such as the Trichogramma, will locate a host (often a caterpillar or an egg) and use a needle-like organ called an ovipositor to inject its own eggs inside the victim.
As the wasp larvae hatch, they consume the host from the inside out, eventually emerging as adults to repeat the cycle. This method is targeted. Unlike broad-spectrum pesticides, for example, a specific wasp species usually targets only one pest, leaving bees, butterflies, and other beneficial insects unharmed.
Pathogens: Microscopic Hitmen
The smallest hired guns are invisible to the naked eye. These are the bacteria, fungi, and viruses known as microbial biocontrol agents. The most famous of these is Bacillus thuringiensis, or Bt. This naturally occurring soil bacterium produces proteins toxic to specific insect larvae. When a caterpillar eats a leaf treated with Bt, the protein binds to its gut lining, causing it to stop feeding and die within days.
Other microscopic agents include:
- Entomopathogenic Fungi: Species like Beauveria bassiana act like a “living mold” that grows through the insect’s exoskeleton, eventually mummifying the pest.
- Nematodes: Microscopic roundworms that hunt soil-dwelling pests like grubs, entering their bodies and releasing lethal bacteria.
Biocontrol: Successes and Failures
The history of biocontrol is a tale of spectacular wins and cautionary disasters:
- The Prickly Pear Victory
In the early 1900s, the Prickly Pear cactus (an invasive species) overran 60 million acres of Australian land. The solution? Introducing the Cactoblastis moth from South America. Its larvae bored into the cacti so efficiently that, within a decade, the “Green Desert” was reclaimed for agriculture. It remains one of the greatest successes in ecological history.
- The Cane Toad Disaster
Conversely, the 1935 introduction of the Cane Toad to Australia to control cane beetles is the ultimate warning against “unhinged” biocontrol. The toads didn’t eat the beetles (which lived high on the stalks), but they did eat almost everything else. Lacking natural predators and being highly toxic, they became a massive invasive threat themselves.
What’s the takeaway here? Modern biocontrol requires years of rigorous quarantine and host-specificity testing before a new agent is ever released into the wild.
The Future of the “Hired Gun”
As we approach 2030, the demand for “pesticide-free” and “residue-free” food is fueling a boom in the biocontrol industry. We are transitioning from a philosophy of eradication to one of management, with maintaining a balance as a primary goal. By using nature’s hired guns, we’re not just protecting trees and crops; we’re restoring the intricate web of checks and balances that kept the world green long before the first chemical factory was built.
Educational materials on biological control are widely accessible through agricultural extension services and conservation organizations, such as RI Tree. These materials— ranging from “Quick Tips” for home gardeners to technical guides for farmers and more—are often called “Field Guides” or “Pest Notes.”
