What are Caterpillars?
Caterpillars are the larvae stage in the life cycle of butterflies and moths. Because many caterpillars eat leaves, some species are serious plant pests – one of the most common garden caterpillars, that of the cabbage white butterfly, for instance, can devastate brassica crops.
How to get rid of caterpillars
The most effective way to get rid of caterpillars is to remove them early and combine physical removal with targeted treatments. Start by checking plants regularly, hand-picking visible caterpillars, and washing leaves with water. For ongoing control, use natural treatments like neem oil or biological controls such as Bacillus thuringiensis (Bt), which targets caterpillars without harming beneficial insects.
How to identify caterpillars in Australia
Caterpillars vary widely in size, colour, and appearance, which can make identification challenging. Looking at their colour, markings, size, and the plants they are feeding on can help narrow down the type.
Pale green caterpillars covered in short, velvety hairs
These are the larvae of the small cabbage white butterfly (Pieris rapae) – the cabbage white found in Australian gardens. They are smaller and less obvious than their larger counterparts but can still cause significant damage. They are typically found on brassicas and leafy greens, including cabbage, rocket, bok choy, and other Asian greens.
Small pale-green caterpillars, tapered at both ends, up to about 12mm
These are diamondback moth caterpillars (Plutella xylostella) – Australia’s cabbage moth. They wriggle and drop on a silk thread when disturbed, and leave characteristic see-through ‘windows’ in leaves. They’re most often found on brassica vegetables.
Green to brown caterpillars with faint pale stripes, feeding in groups when young
These are likely cluster caterpillars (Spodoptera litura), a common Australian garden pest. They feed in groups when young and can rapidly defoliate plants. They’re found on a wide range of vegetables and ornamentals, including brassicas, beans and lettuce.
Pale green to brown caterpillars, often boring into fruit or cobs
These are likely heliothis or corn earworm caterpillars (Helicoverpa spp.), a major Australian garden and crop pest. They’re found on tomatoes, corn, beans and many other vegetables, often boring directly into the fruit or cob.
Hairy caterpillars, often found in groups inside silk nests on wattles
These are likely processionary caterpillars. Their hairs can cause skin and eye irritation, so avoid handling them directly.
Caterpillar damage and symptoms
Most caterpillars are active in spring and summer. Large cabbage white butterfly caterpillars eat holes in the leaves of cabbages. The caterpillars of the small cabbage white butterfly and the cabbage moth tend to feed at the heart of cabbages. Box tree caterpillars produce webbing over their feeding area and can strip a box plant of all its leaves.
How to get rid of caterpillars (step-by-step)
Step 1: Identify the caterpillar
Check your plants for chewing damage, droppings, or visible caterpillars. Identifying the species helps determine whether control is needed, as not all caterpillars are harmful.
Step 2: Remove caterpillars by hand
Pick caterpillars off plants and dispose of them. This is one of the quickest and most effective methods for small infestations.
Step 3: Spray leaves with water
Use a strong jet of water to dislodge caterpillars and eggs from leaves, especially on the undersides.
Step 4: Apply a treatment
Use an appropriate treatment such as neem oil, insecticidal soap, or Bt to target remaining caterpillars. Repeat as needed.
Step 5: Remove heavily damaged leaves
Prune affected foliage to reduce populations and help plants recover.
Step 6: Monitor regularly
Check plants frequently, especially in spring and summer when caterpillars are most active.
What are the best caterpillar control and treatment options?
So, how to get rid of caterpillars in your garden? Here are a few different ways to get rid of caterpillars on plants, ranging from natural and biological to chemical.
Natural treatments
Natural options include hand removal. Pick eggs and caterpillars off the leaves (they often feed at night so a torch might come in handy) and remove them to a site where any damage will be less harmful. Other options include spraying with water, using neem oil, and biological controls, such as a mixture of pathogenic nematodes, including Steinernema carpocapsae. The nematodes enter the caterpillars’ bodies to infect them with a bacterial disease. Spray the product directly onto the caterpillars during damp weather at least three times to control the population. Natural treatments are effective for most garden infestations and are safer for beneficial insects.
Chemical treatments
Chemical systemic insecticides can be used for severe infestations, but should be applied carefully and according to instructions to avoid harming beneficial insects. For best results, spray at the first sign of infestation and re-apply when necessary. Before you treat caterpillars on fruit and vegetables, always check that the insecticide is approved for use on edible crops. To protect bees and pollinating insects do not apply to plants when in flower. Do not use where bees are actively foraging. Do not apply when flowering weeds are present.
Preventative methods
Prevent caterpillars by inspecting plants regularly, using netting to block egg-laying moths and butterflies (make sure the netting does not touch the plants as the adults can still lay eggs through it), and encouraging natural predators like birds and beneficial insects. Birds such as willie wagtails, superb fairy-wrens, magpies and butcherbirds eat caterpillars, so try to attract these creatures into your garden with dense native shrubs, a bird bath and nest boxes.
Before you treat caterpillars on fruit and vegetables, always check that the insecticide is approved for use on edible crops. To protect bees and pollinating insects do not apply to plants when in flower. Do not use where bees are actively foraging. Do not apply when flowering weeds are present.
How to prevent caterpillars
- Birds such as bluetits, great tits, blackbirds and robins eat caterpillars, so try to attract these creatures into your garden by providing food and nest boxes.
- Protect brassica crops like cabbages and sprouts with fine netting or horticultural fleece to prevent adult butterflies and moths from laying eggs on the crop. Make sure the netting does not touch the plants as the adults can still lay eggs through it.
FAQs
How do I identify a caterpillar in my garden?
Look at its colour, markings, size, and the plant it’s feeding on. Caterpillars are usually found on or near their host plants and often leave visible chewing damage.
What’s the fastest way to get rid of caterpillars?
The quickest method is to hand-pick caterpillars and follow up with a targeted spray like neem oil or Bt to control remaining larvae.
Do caterpillars come back every year?
Yes, caterpillars often return each year as part of the life cycle of moths and butterflies, especially in spring and summer.
Are all caterpillars harmful to plants?
No, only some species are considered pests. Many caterpillars are harmless or play an important role in the ecosystem.
