Constant battles are being waged in your garden, some plant to insect, others insect to insect, and even more, human to insect.

Words Kim Syrus

Across the insect spectrum there are those that like to chomp and infest plants; these, we commonly label as “pests”. Then, there are the insects that pollinate, or feed on other insects; these, we commonly label as “friends”. While there always seem to be pests about, encouraging friendly insects into our gardens provides an important balance.

When the insect equilibrium is pest-favoured, it is the gardener who needs to intervene by picking off the nasties, or spraying plants to reduce pest numbers. But having high numbers of insects that prey on other insects, actually helps bring natural order to the yard.

The key to bringing in friendly insects is simple … plants. Plants provide important food and habitat, and diversity in plantings is also important. Adding different flowering and foliage types across the yard gives beneficial insects many different “home” options. Flowers are, of course, high attractors. So the more year-round colour you can provide in your garden, the better.

The idea is to build up generations of good bugs, and you can do this by avoiding chemical sprays and insecticides, which can affect the good bugs, too. You can also “buy in” good bugs. Businesses, such as Bugs for Bugs, can supply both commercial and home quantities of a large range of friendly insects.

Bad Bugs
Cabbage white butterfly
Flitting cabbage white butterfly may animate an Adelaide veggie garden, but this insect’s caterpillar stage creates great angst amongst keen brassica growers by chewing holes through leaves and munching new seedlings. Elongated egg clusters laid on the underside of leaves quickly hatch and the larvae get busy eating. Lacewings and ladybirds help keep their numbers down by feeding on both eggs and young larvae, while parasitic wasps lay eggs inside the cabbage white butterfly grubs.

Citrus gall wasp
Unusual looking lumps and bumps, called “galls”, on the branches of your citrus trees are the result of a visit from the citrus gall wasp. Once the eggs hatch in early summer, the larvae burrow through the bark and feed. This irritation causes galls to develop around the affected sites. Adult citrus gall wasps emerge from these galls around mid-October to early November, so stopping this happening is vital. Grab your snips and cut off any stem or branch below the gall and place in general waste, not green waste. Applying a kaolin clay solution across the entire canopy and branches before adults are on the wing disrupts the egg laying cycle.

Mealybug
As any indoor plant-lover will attest, one of the hardest insects to deal with is mealybug. The small, distinctive wool-like bodies can be found from tips to roots. Tapping into the phloem, mealybugs feed on sap, taking up nutrients and reducing plant vigour. They can quickly build up numbers and large colonies will see plants rapidly decline. Regular checking of your indoor plants is essential. Look under leaves, along stems and around the base. If mealybug is found, isolate and treat by dabbing methylated-soaked cotton buds onto the pest. Otherwise, using horticultural oil and Neem Oil sprays can also help.

Scale
Found along plant stems, on leaves and on fruit, scale is a pest that literally sucks the life out of plants. Mostly small and flat with a protective waxy oval cover, there are hundreds of different types of scale in Australia that affect a wide range of outdoor and indoor plants. Signs that scale has infested a plant include stressed growth, yellowing leaves, sticky residue on stems and foliage and ants running through the canopy.  Lacewings and ladybugs feed on scale, so having good numbers of these in the garden is a great help. Targeted horticultural oil sprays smother scale to quickly reduce populations. Follow-up sprays will help keep them in check.

Slugs and snails
The only difference between slugs and snails, is that the latter have shells, but both these soft-bodied gastropods love our gardens a bit too much. Autumn rains awaken their summer slumber, as well as their appetite. Even though their average speed is one millimetre per second, they can wreak havoc. The “pick and crush” method has been a time-honoured snail-control trick for many gardeners, while beer traps (using full strength beer poured into a low-lying container and placed adjacent vegetable patches), puts a real dampener on their nocturnal celebrations. Birds such as magpies and kookaburras, along with blue tongue lizards, all have an appetite for snails and slugs and help keep numbers down.

Good Bugs
Ladybirds
One the cutest and most beneficial garden friends, ladybirds are amazing pest stoppers. Its larval “ugly duckling” tigers are often mistakenly thought of as a problem insect – but nothing could be further from the truth. These tigers actually devour aphids, scale, mealybugs and plenty more at a rapid rate. Adult ladybirds keep up the pest-eating pace too, as well as being good pollen eaters, so plant plenty of nectar-filled blooms in the garden, please.

Lacewings
Native across South Australia, lacewings help control aphids, scale, mealybug and lots more sap-suckers in the yard. The adults have large lacey wings (hence the name) and feed on pollen and nectar, so it’s the larvae that does the heavy lifting when it comes to pest control. These larvae, known as “antlions”, are grubs whose huge jaws projecting from the front of the head, are extremely effective at seizing, holding and devouring prey.

Parasitic wasps
Relying on a host to complete all, or some, of its life cycle, parasitic wasps have developed a range of clever ways to use pest insects. Aphidius rosae is a tiny wasp that exclusively targets rose aphids by laying eggs inside the aphid. The eggs hatch, eat out the inside, and when adult-time calls, break out of the now-deceased aphid’s abdomen leaving behind a bronzed exoskeleton with a hole in its backside. Seeing bronzed lifeless aphids on your roses is a great sign the parasitic wasp is about. 

Slaters
Lift a garden sleeper or pot and there is a fair chance that small, greyish, armadillo-like insects called slaters will scatter. Nocturnal creatures, they head out across the yard in search of organic matter to munch and compost, helping return valuable nutrients to the soil. Slaters have been known to chow down on new seedlings when other food sources are not available, so keeping additional leaf mulch around helps distract them. Growing plants in raised beds also separates them from the slaters.

Spiders
Walking into a spider’s web at night is likely to set off a quick dance and much body and head rubbing. But while we are not the spider’s prey, lots of pests are. Spiders help control a wide range of insects. Garden orb weavers are common in South Australian gardens, spinning wheel-shaped webs between trees and across pathways. Hiding away during the day, they busily spin out webs to catch mosquitoes, moths and many winged, night-active insects. If you find a spider in the yard, relocate rather that squash.

 

This article first appeared in the Autumn 2024 issue of SALIFE Gardens & Outdoor Living magazine.