The Role of Natural Predators in Controlling Pests in the Garden

 

Garden pest control can be simple. The best way to keep pest populations at bay is to let other creatures eat them.

Birds, frogs, spiders, beetles, parasitic wasps, hoverflies and many others are what gardeners call “beneficials”. These natural predators, quietly keep pest numbers in check, turning your garden into a living, self-regulating system. When we rely on chemical sprays for pest control and constantly tidying of beds, we remove the very insects and animals that control pest populations. The result? We end up fighting every pest outbreak alone. If your garden has natural predators, you won’t have such a problem with controlling pests.

For more on why pests appear in the first place (plant “frequency”, soil health and imbalance), see Garden Balance: How to Let Nature Do the Pest Control Work.

 

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How to Build a Mini Food Web in Your Garden

 

A healthy garden is a simple food web:

 

• Soil organisms break down leaves and organic matter.
• Plants grow in that fertile, living soil.
• Insects feed on plants and decaying material.
• Birds, spiders, frogs and beneficial insects feed on those insects.

 

Your job is to support each link, and by so doing, support the natural eco-system that keeps garden pests in check:

 

Mulch:
Mulching your garden creates habitat for beneficial insects. Living mulch, bark chips or stone chips (which are also rich in good minerals) all give ground-dwellers a place to live and hunt.

 

Bird habitat:
Bird boxes, feeding stations and water stations bring birds in. One of the best ways to house birds is to allow a small section of the garden to become a thicket. Birds, insects, lizards and other small creatures love making their homes in these “super natural” zones.

 

Aquatic habitat:
Shallow ponds, birdbaths or basins introduce frogs and aquatic insects that eat flies, moths and worms.

 

Long grass:
Some birds nest in long grass. It’s often best to cut a grass and perennial section back after ground birds have hatched and you can see them walking around with their chicks.

 

Permeable boundaries:
Clearview fences are popular, but they can trap wildlife. Cutting small holes along the base allows creatures like tortoises, with ground hugging chicks, birds, reptiles and frogs to move and migrate between gardens.

This is how you turn a single garden into a connected, living habitat.

 

 

Know Your Garden Pest Control Allies — Beneficial Insects, Spiders & Predators

 

Lacewings (Chrysopa spp.)

 

What they eat
Lacewing larvae attack almost any soft-bodied insect, including:

 

• Aphids
• Mites
• Whiteflies
• Mealybugs
• Thrips
• Scale crawlers
• Caterpillars
• Psyllids
• Many insect eggs

 

A single larva can kill 30–50 aphids a day.

 

How to identify

 

• Eggs:
  Individual white eggs laid on the ends of inch-long stiff threads.
  → If you see these, don’t destroy them. They’re a sign your garden is recruiting its own pest control.
• Larvae:
  They look like tiny crocodiles. They eat most of the problem pests, especially aphids, and also feed on mites, other small insects and insect eggs.

 

Adults:
Delicate, pale-green insects with large, gauzy wings.

 

Ladybirds (Ladybugs)

 

What they eat

 

Ladybirds are aggressive predators of:

 

• Aphids
• Mites
• Scale crawlers
• Caterpillars
• Beetle eggs and larvae (including Colorado potato beetles)

 

How to identify

 

• Adults:
  Dome-shaped beetles in red, orange, yellow or black, usually with spots.
• Larvae:
  Long, dark, and slightly spiky, often with orange or yellow markings. Many people mistake them for pests, but they’re even hungrier than the adults.

 

Plants that attract hoverflies & ladybirds
Bachelor’s Button, beans, cacti, calendula, coneflowers, coriander, chives, cosmos, dandelion, dill, fennel, feverfew, gardenias, geranium, grapes, hibiscus, marigold, mustard, mint, parsley, peas, Queen Anne’s Lace, roses, statice, strawberries, squash, sunflower, tomatoes, wild carrot, yarrow.

 

Dandelion is a very beneficial “weed” for the soil. As far as possible, don’t weed it out. It also makes a beneficial tea for humans.

 

 Hoverflies (Syrphid / Flower Flies)

 

Also known as syrphid flies, predatory aphid flies or flower flies.

 

What they eat

 

• Adults: pollen and nectar (important pollinators).
• Larvae: soft-bodied insects like aphids and mealybugs.

 

Larvae can consume 200–800 aphids in 7–10 days and play an essential role in suppressing pest populations.

 

How to identify

 

• Adults look like small bees that hover and then dart away quickly. They do not sting.
• Eggs are white, oval, and laid singly or in groups on leaves.

 

Larvae are half-inch maggots in green, yellow, brown, orange or white and look like smooth caterpillars.They raise up on their hind end to catch and feed on aphids, mealybugs and others.

 

Parasitic Wasps and Flies

 

Parasitic Mini-Wasps

 

• Parasites of a variety of insect pests.
• They do not sting humans.
• Their stingers have been adapted to allow females to lay eggs inside the bodies of insect pests.
• The eggs hatch and the young feed on the pests from the inside, killing them and leaving hollow “mummies”.

 

Braconid Wasps

 

• Feed on moth, beetle and fly larvae, moth eggs and various insect pupae and adults.
• If you see lots of white capsules on the backs of a caterpillar, these are braconid cocoons.
  → Leave the dying caterpillar alone – the wasps are doing the work.

 

Ichneumonid Wasps

 

• Control moth, butterfly, beetle and fly larvae and pupae.
• Often slender and long-bodied with an extended “tail” (ovipositor) used to lay eggs into hosts.

 

Tachinid Flies

 

• Parasites of caterpillars (corn earworm, imported cabbage worm, cabbage loopers, cutworms, army worms), stink bugs, squash bug nymphs, beetle and fly larvae, some true bugs and beetles.
• Adults are about 1/3 to 1/2 inch long.
• White eggs are deposited on foliage or directly on the host’s body.
• Larvae are internal parasites, feeding within the host’s body fluids until the pest dies.

 

“Bug” Allies and Predatory Mites

 

 

 Minute Pirate Bugs (Orius spp.)

 

• Tiny (about 1/20 inch long).
• Feed on almost any small insect or mite, including thrips, aphids, mites, scales, whiteflies and other soft-bodied arthropods.
• Particularly attracted to thrips in spring.

 

Damsel Bugs (Nabis spp.)

 

• Usually dull brown and resemble plant bugs that are pests.
• Heads are longer and narrower than most plant-feeding species – the better to eat with.
• Feed on aphids, leafhoppers, plant bugs and small caterpillars.

 

Big-Eyed Bugs (Geocoris spp.)

 

• Small (about 1/4 inch long), greyish-beige, oval-shaped bugs with large, obvious eyes.
• Feed on many small insects (leafhoppers, spider mites), insect eggs and mites as both nymphs and adults.
• Eggs are football-shaped, whitish-grey with red spots.

 

Phytoseiulus

 

A predatory mite that feeds exclusively on spider mites.

 

• Can devour several dozen mite eggs in a day and two to three adult spider mites.
• A powerful natural ally in keeping red spider mite populations under control.

 

Spiders: The Misunderstood Allies

 

 

Recognising “good” and “bad” spiders is a skill you can develop over time. Most spiders in the garden are highly beneficial, eating ants, cucumber beetles, flies and other small prey. Many of their prey are harmful garden pests, though they may also occasionally feed on beneficial insects like ladybirds and predator flies.

 

Black widow spiders are poisonous and most of us know about them. If in doubt, look for a red spot on the body. They are not inclined to attack you, but if you accidentally touch one it may bite in defence; then you should get treatment. They’re usually found in dark shady places, sometimes under vegetables.

 

Once you become familiar with different spiders, you’ll start to see them as part of your diverse ecosystem rather than something to fear.

 

Common Garden Spiders

 

• Yellow garden spider
• Crab spiders
• Lynx spiders
• Wolf spiders
• Cellar spiders / Daddy long legs

 

Yellow Garden Spider

 

• Females are bright yellow and black; males are smaller and dull brown.
• The web has a distinctive zigzag down the centre.
• Often found in slightly sheltered, sunny areas protected from the wind and may stay in the same place for months.

 

Yellow garden spiders are not aggressive and won’t bother you if you don’t bother them. Left alone, their large webs entrap insects, including pests like cucumber beetles and stink bugs. Because they are large, bright and easy to see, bites are rare; if they do bite, it feels like a sting but is not typically dangerous.

 

Crab Spiders (Flower Spiders)

 

• Often coloured to disguise themselves in flowers. Some can even change colour like a chameleon.
• Do not spin webs.
• Sit in flowers and ambush visiting insects, hence the name “flower spiders”.

 

They eat flies and other small insects and are not harmful to humans.

 

Lynx Spiders

 

• Sit on flowers and foliage, waiting for prey to approach.
• Extremely fast, which helps them chase down prey.
• Bristles on their legs help them grab and hold onto the insects they catch.
• Many have elongated bodies, which helps differentiate them from crab spiders.
• Bright colours help them blend into the plants and make them a joy to spot in the garden.

 

They hunt insects on flowers and are very good natural pest predators. They do not have nests, but rather pounce on their prey.

 

 Wolf Spiders

 

• Use speed to hunt down and catch prey.
• May hide in burrows and pop out to ambush insects as they wander by.
• Eat crickets, grasshoppers, ants and flies.

 

Although they look scary, they are not considered highly poisonous and prefer to avoid humans.

 

 Cellar Spiders (Daddy Longlegs)

 

• Very long legs and small, delicate bodies.
• Often seen in corners, under eaves or in quiet, sheltered spots.

 

They feed on a variety of small insects, spiders and worms, and will also eat decaying material — helping clean up the garden as well as eating pests.

 

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How to Attract and Keep Your Allies

 

 

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• Mulch beds generously.
• Leave some leaf litter, bark chips or stone chips.
• Add logs, rocks, hollow stems and small brush piles.
• Allow one corner of the garden to become a thicket for birds, insects and lizards.

 

Add Water

 

• Provide shallow dishes, birdbaths or small ponds.
• Add pebbles so insects can land and drink safely.
• Aquatic habitats bring frogs and dragonflies that feed on flies, moths and mosquito larvae.

 

Plant for Nectar and Habitat

 

• Use a mix of flowering herbs, perennials and shrubs.
• Aim for blooms across multiple seasons to support predators year-round.

 

Welcome Birds

 

• Install bird boxes and feeding stations.
• Leave areas of long grass for ground-nesting birds.
• Keep some seed heads and old stems over winter.

 

Avoid Chemical Pesticides and Fertilisers

 

• Avoid chemical fertilisers and pesticides that sterilise soil and kill beneficials.
• Even organic products should be used sparingly and only when necessary.
• For specific pest remedies and recipes (neem oil, homemade insect soaps, Beauveria, Bt and more), see Targeted Treatments: Natural Remedies for Common Garden Pests.

 

Observe the Biodiversity in Your Garden At Work

 

Spend a little time each week just watching:

 

• Check flowers for hoverflies, bees and crab spiders.
• Look under leaves for lacewing eggs and ladybird larvae.
• Notice where spiders build their webs.
• Listen for birds and watch what they’re eating.

 

Biodiversity increases quietly over time. If your garden hums, rustles and moves, it’s working.

 

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The Big Picture

 

A single lacewing larva can eat up to 50 aphids a day. A single ladybird can consume thousands of pests in its lifetime. Spiders, beetles, parasitic wasps, hoverflies and bats are constantly reducing pest numbers without you lifting a finger. Give them habitat, water and refuge, and they’ll do most of the pest control for you!