Oct. 28, 2026
The Dawes Arboretum has many sustainability practices including using insects to combat harmful bugs naturally.
Each year when spring arrives, Dawes Nursery Manager Bridget Reed, they know it’s time to order insects from the internet.
Purchasing beneficial insects is just one part of the plan Reed uses to manage the health of the nursery. This action is part of Integrated Pest Management (IPM), meaning an “effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices,” according to the EPA.
Reed compared IPM to not putting all your eggs in the same basket.
“They can’t become resistant to their natural predators,” said Reed. “Beneficial insects are a leg of that strategy that allow you to diversify better and not rely on one thing.”
Every year, Reed investigates what pests The Arboretum is seeing inside its greenhouses, either what is currently present or what they have struggled to control in the season prior. Based on that collected data, they fire up their computer and head to Arbico Organics, a site that sells beneficial insects.
Common pests that Dawes deals with are aphids, thrips and mites. Because they are extremely small is size, for example, an aphid can range in size from .0625 inches to more than 0.125 inches, Reed said you don’t necessarily monitor whether you see them, you can also monitor for their damage.
Although each year brings its different challenges, an insect that Reed has purchased year-after-year is green lacewing. Its whole job in its adult life stage, essentially, is to lay eggs and die. In its larval stages, it is a predator against aphids, thrips, whiteflies, leafhoppers, spider mites and mealybugs, which are common garden pests.
They usually purchase insects in an egg form as it’s more value for the dollar. When it’s time to put the eggs in the greenhouse, Reed sprinkles the eggs on the plants right after watering or after spraying the plants. These eggs transform into larvae, which eat soft-bodied insects that don’t have an exoskeleton, such as an aphid.
Reed has purchased green lacewing annually, but she has also purchased minute pirate bugs, assassin bugs, nematodes and more.
If Reed isn’t purchasing a predator, they're purchasing a parasitoid, which means that it lays an egg in the “bad bug” to make a “good bug.”
An example of a parasitoid that they’ve purchased is Aphelinus abdominalis, a parasitoid wasp that hunts aphids. Not only do they lay eggs in adult aphids, but they also eat those that don't get infected with parasites. Once their eggs hatch inside the body of the aphid, the larvae consume the aphid itself and emerge through exit holes at the back of the abdomen. Aphid bodies that have hatched parasitoids are referred to as "aphid mummies."
Over the years, Reed has seen an increase in the native insect population because of this IPM program including the release of beneficial insects. Because of this management tactic, The Arboretum sprays fewer chemical pesticides.
There are still other methods of pest control like simple hand removal or chemicals, but diversifying methods means that populations won’t easily become resistant, compared to if Reed was using one method of removal.
Reed said it was an “old school way” to spray and only spray. If someone is just spraying, they’re not accounting for the entire ecosystem.
Oppositely, it might be necessary to use a pesticide if beneficial insects have been released but they’re doing as much as they can. Sometimes, beneficial insects are outnumbered. That’s when Reed asks an important question: “Is my population high enough that I can sacrifice a few of my good bugs to knock it down?”
Because of the responsible release of beneficial insects, The Arboretum can contribute to having a self-sustaining population. There can also be cost savings by spending less on chemical pesticides.
“It’s worth it to spend more money to safeguard the insects that are neutral and part of our ecosystems,” Reed said.
The nurseries that Reed is protecting holds plants that are for the grounds, the gift shop at Dawes or the four nationally accredited collections.
“Those plants from the collections are priceless,” Reed said. “You can’t even quantify it.”