It’ll happen when you least expect it. Your plants will be growing beautifully, and you feel like you have this whole gardening thing under control. And then – out of nowhere – you see them.
Crawling on the surface of the soil, or maybe clustered together on a stem or under a leaf. The bottom drops out of your stomach and the panic sets in.
What do you do now? Yes, you need to take immediate action to curb your pest infestation before it really takes off, but before you reach for the closest pesticide, consider fighting the latest outbreak with an all-natural biological pest control method as old as time itself.
Biological pest control is a pest management technique that involves using beneficial insects to fight pest infestations. Ladybugs, green lacewings, parasitic wasps, predatory mites, and hoverflies are just a few of the insects used to control pest populations without bringing harm to yourself or your plants.
Read on to learn what exactly biological pest control is, and identify how and when to use it in your indoor or outdoor garden.
What Is Biological Pest Control?
Biological pest control is the use of living organisms to control pest populations.
Kimberly Stoner, Entomologist at the Connecticut State Agricultural Experiment Station explains the relationship between biological control and pests:
“Biological control is the use of living organisms to suppress pest populations, making them less damaging than they would otherwise be. Natural enemies of insects play an important role in limiting the densities of potential pests. These natural enemies include predators, parasitoids, and pathogens.¹”https://portal.ct.gov/CAES/Fact-Sheets/Entomology/Approaches-to-the-Biological-Control-of-Insect-Pests#:~:text=Summary-,Biological%20control%20is%20the%20use%20of%20living%20organisms%20to%20suppress,predators%2C%20parasitoids%2C%20and%20pathogens.
Stoner explains that biological pest control can take one of three forms:
- predatory insects
Predatory insects are insects who consume pests in either their larval stage or adult stage. Ladybugs, green lacewings, and praying mantises are examples of predatory insects.
Parasitoids are insects who act as parasites to host organisms – one example is the parasitic wasps, who lay their eggs inside other insect bodies, and when the eggs hatch they kill the host organism.
Pathogens include bacteria or fungi that are designed to infect a specific host species.
Advantages Of Using Beneficial Insects
Using beneficial insects is one of the best ways to fight pest infestations! Here are some of the benefits:
All-Natural & Chemical-Free
Biological pest control removes all worry about coming in contact with harsh chemicals, either synthetic or organic. While most pesticides are so powerful that they must be diluted or applied sparingly, you really can’t overdo it with predatory insects.
The worst-case scenario that may occur is that the surplus of predators will completely eradicate the prey, causing the beneficial insects to starve to death.
Hands-Free Pest Control
Whereas spraying for pests is a time-consuming task that needs to happen on a regular schedule, biological pest control requires significantly less supervision.
You might not even be able to notice whether or not your predatory insects are initially working because the control happens on such a minuscule scale. Eventually, you will see your pest populations decrease and almost disappear.
If applied correctly, you shouldn’t need to add additional rounds of predatory insects, as the insects will live and reproduce on their own. If your insects do die due to exposure to extreme weather conditions or chemicals, you can always order and release more populations.
Establish Permanent Pest Control
Some predatory insects (like ladybugs and green lacewings) are native to North America. Entice beneficial insects to your garden by planting native perennial plants and nectar-rich flowers.
If even you can’t score free predatory insects, you can order hatching eggs of many of these beneficials online for a reasonable price. If you provide habitat and a constant food source for predatory insects, they won’t go anywhere and you can reap the rewards of biological pest control for seasons to come.
Disadvantages Of Using Predatory Insects
As with anything, there are a few realities that may make predatory insects less than ideal in some situations.
Not Compatible With Chemical Sprays
If you spray your plants regularly, you’ll have a hard time keeping predatory insects around, as these insects are sensitive to chemicals. If you can help it, don’t use any pesticides, fungicides, or synthetic fertilizers in conjunction with beneficial insects.
Results Aren’t Instantaneous
Biological pest control doesn’t always work instantly, and in the most severe infestations, you need to act immediately. It takes some time to order and ship predatory insects, and you do need to account for the time it takes for insect eggs to hatch and multiply to really curb the pest population.
When To Use Biological Pest Control
Now that you know what biological pest control is, you might be wondering when you should use it. Here are two use cases:
Many gardeners introduce predatory insects into their gardens well before the telltale signs of infestation, as a preventative measure. Ideally, you’ll want to keep your initial population of beneficial insects alive (and their consecutive generations) by providing a habitat for them to live and reproduce.
Create habitat for beneficial insects in your outdoor garden by planting a pollinator garden that will provide habitat for insects that need to overwinter. Most beneficial insects, even if their larvae are predatory, actually eat nectar and pollen as adults.
Plant re-seeding annuals and perennial flowering shrubs to provide a food supply for the adults. Diversify your plantings as much as possible to create varied habitats and consistent flowering year-round.
Avoid spraying any kind of pesticide or chemical after you’re released predatory insects, or you run the risk of wiping out the good bugs as well as the bad bugs. Build a “bug bath” by filling a shallow dish with water and a few stones or sticks.
You can introduce biological pest control as soon as you notice the first signs of an infestation. Don’t delay in ordering your predatory insects – infestations are so much easier to cull early on.
Biological pest control is very effective, but predatory insects can only eat so many pests per day – even if that number is in the thousands. Introduce predatory insects as early as possible to prevent the prey population from growing exponentially.
Apply biological pest control early and often for the best results – even in the worst of invasions.
How To Apply Biological Pest Control
Applying biological pest control isn’t difficult, but take care to release predatory insects at the appropriate time and in the correct location for maximum success.
Before you order beneficial insects, make sure to correctly identify the pest(s) in your garden and match them up with the correct predator or parasite. While some beneficial insects are generalist feeders, most specialize in one or more pest species.
Depending on the beneficial insects, they’ll be shipped to you as eggs, larvae, or adults. Whatever species you buy should come with detailed instructions on how and when to release. A good rule of thumb is to release beneficial insects in the early morning or late evening when the insects are most active.
Intentionally place predatory insects close to their prey, and make sure there are blooming flowers around to encourage the nectar-eating adults to stick around. Water the plants before after application to ensure newly-hatched predators have water and to help their bodies adhere to the affected plants.
6 Beneficial Insects To Use (Plus Where To Get Them)
Now that you understand how and when to use beneficial insects, use this guide to determine which insect to use for which pest problem.
The red and black beetles that we all know and love are really vicious aphid-eaters. North America is rich in both native and naturalized ladybug species.
The adults and larvae of both types prey on aphids, mites, and other crawling insects. Ladybug larvae have the signature red and black markings of adults, but they resemble a spiky worm with six legs.
Attract ladybugs to your garden by cultivating wildflowers and native perennial plants, or by planting a sacrificial aphid-susceptible crop, like nasturtiums. Give it a week, and these hungry beetles are sure to find their way to your garden.
2. Green Lacewings
While adult green lacewings feed on pollen and nectar, lacewing larvae have such an appetite for aphids that they’ve earned the name “aphid lions.” Lacewing larvae have been known to consume as many as 1,000 aphids in a day.
Green lacewings hold so much benefit for the garden, managing pest populations when young and pollinating plants as adults.
3. Parasitic Wasps
A diverse family of roughly 100,000 species, parasitic wasps can be categorized by a few different types. The University of Maryland groups parasitic wasps into three categories: Aphelinidae (Aphelinids), Chalcididae (Chalcidids), Encyrtidae (Encyrtids), and Trichogrammatidae (Trichogramma), Braconidae (Braconids), and Ichneumonidae (Ichneumons) wasps.²
Braconid wasps are a favorite among farmers and gardeners, as their larvae eat aphids, cabbage looper, tomato hornworm.
Adult wasps lay their eggs in the hosts’ bodies or eggs, injecting a venom that inhibits the hosts’ body from fighting the wasps. Trichogramma wasps target butterflies and moths, while Encrytids are opportunistic wasps that feed on anything they can.
4. Predatory Mites
Who hasn’t had an issue with spider mites in their garden? Those annoying microscopic arachnids will wreak havoc on everything from houseplants to your outdoor vegetable garden. Fortunately, predatory mites are effective spider mite killers, and these aggressive insects will make quick work of any lingering thrips as well.
Adult hoverflies are often confused for honeybees or wasps, especially as these flies are frequently spotted pollinating flowers. Hoverfly larvae are natural predators of several plant pests, including aphids, thrips, scales, and caterpillars. A pollinator native to North America, hoverflies are an essential piece of a healthy garden ecosystem.
6. Predatory Nematodes
You might have heard about nematodes – these microscopic worms can be either friend or foe in the garden, so be sure to look for the identifier “beneficial” or “predatory” when researching and ordering nematodes.
Predatory nematodes live in the soil and seek out their prey via hunting or waiting for an opportunity to ambush. Once the prey has been located, beneficial nematodes invade the host organism. Dr. Leonard Perry, from the University of Vermont, describes the science behind the attack:
“Once found, the beneficial nematodes enter the grub or other pest through body openings, such as the mouth or openings to the breathing tubes (“spiracles”). These juveniles carry a bacterium (safe for plants and the environment) that they release into the pest blood. These bacteria multiply, killing the pest in two days or often sooner, and converting host tissue to food for the nematodes.³”https://pss.uvm.edu/ppp/articles/nemat.html
There’s hardly a more cold-blooded killer of soil-borne pests than the beneficial nematode. Nematodes are useful in controlling pests that inhabit the soil, including flea beetle larvae, Japanese beetle grub, and cutworms.
Where To Find Insects For Biological Pest Control
Use predatory nematodes in conjunction with airborne predatory insects to attack pests at all stages of their life cycles.
Beneficial insects are easier to acquire than you might think. Online retailers like Arbico Organics carry a wide range of predatory and parasitic insects.
Some seed companies, including Territorial Seed Company, have the more common beneficial insects, like ladybugs and green lacewings, available for purchase. Other retailers of predatory insects include Nature’s Good Guys, GrowOrganic, and even Amazon.
When you have a pest infestation, synthetic chemicals aren’t your only option, and even organic sprays don’t have to be your first choice. Consider introducing biological pest control for the worst infestations, or as a preventative measure for the first outbreak even begins. Better yet, incorporate perennials and flowers into your garden to create a balanced ecosystem of predator and prey from the very beginning.
I hope you found this article helpful. If so, please share it with someone who can use the information.
¹ Stoner, Kimberly, “Approaches to the Biological Control of Insect Pests.” The Connecticut State Agricultural Experiment Station, CT.gov, https://portal.ct.gov/CAES/Fact-Sheets/Entomology/Approaches-to-the-Biological-Control-of-Insect-Pests#:~:text=Summary-,Biological%20control%20is%20the%20use%20of%20living%20organisms%20to%20suppress,predators%2C%20parasitoids%2C%20and%20pathogens.
² Raupp, Mike, Traunfeld, Jon, and Sargent, Chris, “Parasitoid Wasps.” University of Maryland Extension, https://extension.umd.edu/resource/parasitoid-wasps.
³ Perry, Leonard, “Beneficial Nematodes.” University of Vermont Extension, https://pss.uvm.edu/ppp/articles/nemat.html.
About the author:
When not writing content or growing flowers in her native Virginia, you can find Sarah hiking a long-distance trail deep in the woods. Follow along with Sarah’s adventures at http://sarahcolliecreative.com.