How to get good bugs into the garden and keep pests down

December 23, 2024

The thing that changed how I garden was working out that most of what is crawling around out there is either doing nothing to my plants or actively helping. Once you stop treating every insect as a problem, a lot of the spraying stops being necessary, and the garden starts sorting out a fair bit of it on its own.

The one everybody kills by accident

Ladybird larvae look nothing like ladybirds. They are little grey and orange things, a bit alligator shaped, and they crawl about on the leaves looking exactly like something that is eating your plant. They are not. They eat aphids, and they eat considerably more of them than the adult beetle does, so the larva is the one you most want to leave alone.

If you learn one insect by sight, make it that one. There are plenty of photos online and it is worth two minutes.

Who else is on your side

Lacewings. The adults are pale green and delicate. The larvae go through aphids, mites, scale and small caterpillars.
Hoverflies. They hang in the air like a tiny wasp that can't decide. The adults pollinate and the larvae eat aphids.
Bees, both the ones you know and the native ones. A lot of native bees are small, dark and solitary, and people do not realise they are bees at all.
Predatory wasps. Tiny, not the ones that ruin a barbecue, and they lay eggs in caterpillars and aphids.

What actually brings them in

Flowers, and specifically the right shape of flower. Hoverflies, lacewings and the small predatory wasps have short mouthparts, so a big deep flower is no use to them at all. What they want is lots of tiny flat flowers, which means the carrot family: dill, coriander, parsley, fennel and carrots themselves, all left to run to flower rather than pulled out the moment they bolt.

That is the trick, and it costs nothing. Let a few of your herbs bolt on purpose. Alyssum does the same job and flowers for months.

The rest of it is straightforward. Something in flower for as much of the year as you can manage. A shallow dish of water with pebbles in it so they can land. Some undisturbed rough ground, a log or a bit of mulch left alone. And going easy on the sprays, because a broad spectrum insecticide does not read labels and takes out the predators along with the aphids, which is how you end up with a worse aphid problem three weeks later once the predators are gone and the aphids have bred back.

Three old tricks that do less than people think

Crushed eggshells around a seedling. Snails and slugs walk straight over them. It has been tested more than once and it does not hold up. If you want the shells in the garden they are fine going into the compost, they are just not a barrier.

Marigolds repel everything. The nematode effect is real, but it comes from growing a solid block of them and digging the lot in as a green manure, not from popping one next to a tomato. As a flower for beneficials they are worth having. As a force field they are not.

A pot of basil keeps the mosquitoes off. The oils in the leaves do repel, which is why crushing a leaf on your arm does something. A plant standing there quietly is not releasing them.

When you do have to step in

Work out what it is first. Plenty of what gets sprayed is either harmless or is one of the predators.
A soap spray works on contact and does nothing once it dries, which is why it is gentler on everything else. Use a plain soap rather than dishwashing detergent, and do it in the evening, because soap on a leaf in full sun can burn it.
An oil spray smothers scale and aphids and then breaks down, so it is a targeted job rather than a blanket one. Same rule, not in the heat of the day.
For snails, an iron based pellet is the one to reach for. It works, unlike the eggshells, and it is a lot safer around dogs and birds than the old blue metaldehyde pellets.
Feed and water the plant properly. A stressed plant is what the pests find first, every time.

Shop related products

Multiguard Snail and Slug Pellets 600g. Iron based, and the one I would use where there are dogs or chooks about.
Brunnings White Oil RTU 1L. Smothers scale and aphids on contact, ready to use.
Multicrop EcoPest Oil Insect Spray. Same idea, and useful on citrus.
Multicrop Kocide Blue Extra Fungicide 30g. For when the problem turns out to be fungal rather than an insect at all.

The rest is in pest control, and the seeds for the flowering side of it are in the DT Brown range. The whole garden centre is here, and if you are not sure what you are looking at, take a photo and bring it in and we will have a look at it with you.

Did you know we also stock Cyclone and Gardenmaster hand tools and a range of seed raising and potting mixes in the shop that aren't all on the website. Give us a ring on (08) 8536 4333 to check what is on the shelf.