When you have a pest insect infestation in your garden or landscape, there’s an army of predators ready to take them on… if you don’t kill them first.
These predators are called ‘beneficial insects’. And they need two things to survive in your garden.
Pest insects. And flowers.
How the beneficials work
Insect lives have four stages: egg, larva, pupa, and adult.
When a mother beneficial insect is ready to lay her eggs she looks for a pest insect infestation and lays them nearby, or in the pest insect. That way she knows her babies will easily find food, when they hatch.
The young babies start eating those pest insects and grow nice and big and fat. Then they’re ready to pupate to turn into adults.
When the new adults emerge, they need to find flowers that will provide them with nectar and pollen so they’ll have the energy to mate. Then the females will find a place to lay their eggs.
These beneficial insects are carnivores. They eat insect ‘meat’, usually in their larval stage.
Depending on which carnivorous beneficial insect it is, the mother may lay her eggs on a leaf where there are pest insects feeding on leaves. Or they may lay their eggs in or on another insect, like an aphid or a caterpillar.
When the eggs are laid near a pest infestation, the hatched larvae crawl over to the pest insects and start eating them. Like a ladybug larva that devours aphids.
When the eggs are laid in a caterpillar, the hatched larvae eat the insides of the caterpillar, killing it, leaving the vital organs for last to eat all the live insect tissue. Like tiny tachinid flies devouring a tomato hornworm, from the inside. Then they pupate and emerge as adults.
Not all the beneficial insects operate the same way. Some eat other insects in their larval and their adult stage. Like the ladybug. And some need flowers at various times.
But most need pollen and/or nectar to complete their diet. And not just any flowers will do. Like how pollinators need certain flowers, the same is true for the beneficial insects. Which, makes the beneficial insects pollinators, too! But first…
Let’s see who’s working for you in your garden
It takes some keen observation to find all these helpful bugs, but knowing what they look like gets you started. To see some of them having a hand lens or a magnifying glass handy will help you see a new world in action in your garden. (Please beware of getting sun rays into your eye through the hand lens!)
Meet some of the beneficial insects:
Parasitic wasps (they don’t sting us, and some are very tiny, lacewings, ladybugs, beetles, predatory mites (they eat other mites), true bugs, true flies (like hoverflies), spiders (please get over this fear), mantids (like praying mantids, there are different ones), and more.
Now, let’s see who’s eating your plants
These are the insects (and mollusks) that eat foliage, or roots: Aphids, spider mites, scale, caterpillars, slugs and snails, thrips, grasshoppers, whiteflies, psyllids, pest beetles, mealy bugs, corn earworms, and more.
What happens when you kill the pests
When you spray with a pesticide, whether it’s a synthetic or a natural one, you also kill the beneficial insects that are present. And even though you kill the pests, any beneficials that remain are left without their food source. They do not procreate. Your landscape’s beneficial insect population declines and the pests that survive the spraying or that come in later have fewer enemies to keep them in check. The beneficials will need more time to catch up.
So you have your pest cycle all over again. Which means more control and work for you, and so on. And there’s also the impact those measure have on pollinators.
But you can have your garden and landscape plants under full control of beneficial insects, avoid the trouble of spraying or using other pest control measures, and avoid harming the pollinators this whole planet needs for survival. Instead maintain a healthy population of the insects whose very job it is to consume populations of pest insects.
How can you feel sure you can count on your beneficials?
There are two things you need to do to let a beautiful, powerful, process handle your pest control for you.
First, allow a pest population to develop without you correcting it. Don’t panic. This will attract beneficial insects. And the method Mother Nature has devised to attract them is a process of amazing, gorgeous complexity!
You see, insects respond to scents that inform them and influence their behavior. When plants get eaten by insects, they send out scents that signal the situation and that attracts the right type of predator insect to the type of prey that’s on them.
In other words, the plant that’s getting eaten calls the right bugs for help with that problem. And it works.
So let the pests build a population, don’t panic, and the beneficials will come and clean it all up.
The other thing you need to do is plant the flowers that feed the beneficials. This will boost their populations to give you quicker response.
What flowers are good for the beneficials?
Ok, now you have a great excuse for having a flower garden! Some flowers are good as cutting flowers, and most are good for the pollinators, too. And like for the pollinators, different flowers have different ingredients in their nectar. Nectar isn’t all sugar water—not at all! It also has amino acids, lipids, stimulants, organic acids, proteins, and even microbes for insect guts.. You want a diversity of the right flowers; the best fed beneficials are the ones who can do more pest control and make the most babies.
Asters, Heliopsis, native buckwheat (Eriogonum species), Boltonia, calamint, cilantro, cosmos, coreopsis, dill, all daisies, Echinaceas, elderberry, fennel, Erysimum (wallflower, like ‘Bowles Mauve’), feverfew, goldenrod, mountain mint (Pycnanthemum), all oreganos, sweet alysum, black-eyed susans, verbena, and yarrow are all good choices.
Fortify your garden with beneficial insects by planting a variety of flowers attractive to them. Like for pollinators, natives are a plus.
My experience with beneficials
I’ve had landscapes and gardens for decades and never had any pest problems. I’ve always had a variety of flowers just because I liked to grow them and cut them. Being an organic grower, I never would have sprayed anything.
The one time I felt I may need to resort to some kind of insecticide was when I notice curling on the leaves of my Santa Rosa plum tree. It was spring. Looking closer at the underside of the leaves, I found a phenomenal number of aphids all sucking away in unison! Shocked, fear drove my thoughts into what non-toxic or even toxic poison should I use to stop this.
But I also noticed adult ladybugs, larval ladybugs, ladybug pupae, and soldier beetles. So I thought…I hope they can handle this infestation.
I had young children then and was quickly distracted. About two weeks later I went out to check on the plum tree. Not one single aphid. Clean as a whistle. The curled leaves were still curled, but they were getting buried in new growth.
This works. Let it work for you in your landscape.
Observe them, and have fun doing it!
A flower like a cilantro, dill, or parsley flower attracts so many parasitic wasps. It’s fascinating to just sit in the garden and watch them flit around. Many of them are so tiny they’re barely visible. I guarantee they’ll be there. See if you can find lacewings, hoverflies, and even ladybugs on your flowers or near your aphids. And don’t forget the beetles in the soil are helping, too.
An exception to this is when there is a non-native invader pest species. Sometimes these need specific pesticide treatment, or sophisticated biological strategies.
For lots more information and details about this truly fascinating topic, read this book: Attracting Beneficial Bugs to Your Garden, by Jessica Walliser, Cool Springs Press, 2022.
Related Reading:
Our Gardens Can Save the Bees—Much More Than You Think!
The Flowers That Can Save the Bees
Beneficial Insects Need Food: Pests!
To learn about flowers that are good for beneficials and are also great cutting flowers, see my other website growyourflowers.com, and find feverfew, Shasta daisies, Echinaceas, and yarrow, all in the perennials section.