The Caterpillar Conundrum: Caterpillar Pests in and Around Perth

Among the many pests plaguing the Perth area and surrounding regions of Western Australia, one might seem like something that most pest control experts might give little attention: the caterpillar. After all, caterpillars represent the larvae stage of moth and butterfly life cycles, and – aside from the occasional moth infestation inside a home – few people view those winged creatures as much of a threat. The problem is that caterpillars are considered to be major agricultural pests everywhere they are found. Moreover, caterpillars usually tend to do more damage to crops than adult moths ever manage.

Built for Survival

Caterpillars are impressive creatures in their own right. Though they cannot yet fly – that ability is not gained until they fully mature into their moth or butterfly forms, they still manage to cut a ferocious path across their landscape. They are literally eating machines that can, in large numbers, strip the leaves from an agricultural field in rapid fashion. They also mature quickly, with many of them able to increase their bodyweight many hundredfold in a relatively short period of time.

Most are herbivores, preferring plants above all other food sources. Some are even specialized herbivores that seek out certain types of plant life to the exclusion of all others. As is true with most species, however, there are caterpillars of all kinds, tastes, and preferences. Some prey on other insect eggs, or larvae. There are even some in certain parts of the world that prey on other caterpillars.

Like many pests, caterpillars are primarily nocturnal in nature, choosing to hide in plants and trees during the daylight hours. They then come out at night to feed on the leaves of any plants they find in the area, or other food sources that they are accustomed to consuming. All of that feeding comes at a cost to humans, of course, since caterpillars are among the most destructive agricultural pests in the world.

The White Cedar Moth Caterpillar

Around the Perth area, there are few environmental pests that pose more of a nuisance than the Cape Lilac Tree Caterpillar – otherwise known as the White Cedar Moth Caterpillar. These caterpillars Are a dark brown color with bright orange legs and a clearly identifiable yellow streak down their back. They grow to be about 4 centimeters long, and are covered in bristles. Those bristles can cause an allergic reaction in some humans, and are believed to cause miscarriages in horses.

Each year in the fall, these caterpillars show up in the area in large numbers ready to destroy crops, strip trees and other plants of their leaves, and even invade homes. Yes, this pest is so pervasive that it navigates its way around barriers, over roads and pathways, and into homes – often in groups as large as several hundred at a time. Moreover, they travel over ground quite rapidly, often covering as much as 80 meters in a very short period of time.

In their natural outdoors environment, they are particularly attracted to the Cape Lilac Tree, and will greedily consume every leaf on any tree they infest. There have been many documented cases where several thousand of the creatures have been found in the branches, nooks, and crannies of just a single tree. Because they are nocturnal, they hide near the base of their chosen trees during the day and emerge at night to climb up and feed.

And that feeding is often nothing short of an all-out attack on the tree’s leaves. Many observers have recounted instances in which they witnessed the trunk of one of these trees almost completely covered in these hungry insects, with the ground surrounding the saturated with their defecation. Once a tree has been completely stripped of its leaves, the communal swarm of caterpillars will venture off in search of its next target tree. That search can bring them into a garage, your car, your home, or just about any other locale that lies in their path.

The trees themselves tend to actually thrive, despite the defoliation efforts of the caterpillars. They are deciduous trees, so the fact that they shed their leaves anyway certainly has something to do with their ability to withstand such constant attacks.

Homeowners in the area are advised by the Department of Agriculture to avoid spraying for the pests. After decades of pesticide use, this species has developed a remarkable tolerance for and resistance to most pesticides. To limit the damage that these creatures do, people should use hessian at the base of the tree trunk to attract the caterpillars during the day. Once they are sheltered beneath that sacking, they can be gathered up and destroyed with insecticide or physical force. Homeowners should recognize, however, that they may have to repeatedly attempt such removal, since these insects are extremely persistent.

The same technique can be used to prevent them from gaining access to a home, garage, or other structure. Roll up hessian and place it at strategic entry points, or apply a spray at any doorways, windows, or other obvious openings.

Home Garden Caterpillar Pest Varieties

In addition to the White Cedar Moth Caterpillar and its destructive attacks on trees, there are a variety of other caterpillar species that can wreak havoc in Perth and across Western Australia. These include various caterpillars that feast on home garden vegetables, and those that attack fruit.

Lightbrown apple caterpillars

This species is native to Western Australia, and can grow up to 20 mm in length. They typically feast on fruit, and prefer orchards and home gardens in isolated areas and a rich abundance of raw materials. They seldom get out of hand, due to the fact that they have a natural predator that keeps their populations in check: the braconid wasp. At times, however, they can grow to be a problem, and can be controlled with weak pesticides that you can find commercially.

Green Caterpillars/ Cabbage White Butterfly caterpillars

These green caterpillars favor leafy green vegetables like those found on cabbage, cauliflower, broccoli and cauliflower. The worm itself can be found in both home gardens and commercial farms. In the former instance, it poses little threat since incursions usually involve only a small-scale pest issue. Where the latter is concerned, however, an infestation can be a major problem. Larvae enter broccoli and other cabbage vegetables, and contaminate it from within. Once that happens, the vegetables are essentially lost.

The fact is that consumers have little patience for discovering caterpillars in their produce. Produce providers know this, and thus will not accept any farm shipments where even a single caterpillar is discovered inside a head of lettuce or a broccoli stalk. When that does occur, it means that the entire shipment to the store is rejected in its entirety, and the grower ends up having to destroy the contaminated shipment. Obviously, that can lead to thousands of dollars in lost revenue – something that no farmer can afford to endure on a regular basis.

As a result, everyone involved at every stage of the produce production process needs to understand how to identify the pest. The caterpillars are a vibrant green color with a yellow stripe and yellow spots. The older larvae can grow to 30 mm in length. Their life cycle typically begins as eggs laid on leaves. Once those hatch within about a week, the larvae begin their stage of development, which lasts for up to three weeks. In that time, they chew round holes through leaves, and spoil the vegetables with their waste.

Monitoring for this pest should begin while the creatures are still in the egg stage. Typically, these eggs can be found on the underside of vegetable leaves. If those are not spotted, routine inspection of vegetables should be conducted to search for signs of their green-brown waste pellets. These searches should be conducted every week to facilitate early detection of infestation. Crops that survive through to harvest without a problem can be sprayed a week before harvest. Experts recommend that professional spraying as the best way to safeguard the crop and maximize your chances of getting it to harvest and market without contamination.


The diamond-back, or cabbage moth caterpillar, is often found on canola. As such, it is considered an economic pest that reduces crop yields and profits. Larvae feed on different parts of the plant as it matures, consuming not only the leaves but the flowers, pods, and buds as well. Due to that destruction and the potential loss of a sizable portion of any infested crop, both natural and chemical control techniques can be used against these pests.

Efforts to conserve crops through the introduction of natural predation have not proven effective in reducing crop loss or negative economic impact. Instead, growers tend to rely on disrupting the moths’ bridging populations by removing weeds prior to planting, and the use of various chemical pesticides. Applications usually need to be reapplied, however, since some larvae populations appear to have developed a resistance to many of the most commonly used pesticides.

Cluster Caterpillar

The cluster caterpillar is among the lesser worm pests in Western Australia. Where they are active, they defoliate plants such as cabbage and damage potato crops. The name is derived from the insect’s mass hatching where as many as 200 eggs can be laid on a single leaf. Upon hatching, all of the caterpillars begin to feast on that same leaf – in a cluster. As a general rule, these pests are unobtrusive. There are occasional outbreaks of heavier activity, but chemical spraying can usually contain those minor threats. Minor infestations can typically be controlled using natural predators like parasitic wasp species.

Looper Caterpillar

Looper caterpillars will consume just about any vegetable or plant, as well as many fruits. They will feed on leaves voraciously. With fruit, they infest in large numbers and feed on the immature fruit to the point where scabs form on the exterior. They tend to leave fruit leaves alone, preferring the meat within. Unfortunately, these spring pests tend to render fruit crops unmarketable, and can severely impact fruit production in any grove.

Because of the nature of these insects’ feeding habits and their heavy activity in the spring months, monitoring should begin early in any growing season. Experts have focused on close inspection of fruitlets to detect signs of feeding as early as possible. The goal is to prevent as much damage to crops as possible. Studies of the insect have revealed that at least one parasitic wasp species seems to prey on it, so natural control agents do exist – though they may not be much help in more controlled environments. Fortunately, there are pesticide products that can be applied to aid in controlling the population and protecting the produce.

Eggfruit Caterpillar

Eggfruit caterpillars are borers by nature, and worm their way into aubergine, where they eat to their heart’s delight. They leave tunnels throughout the eggplant – usually filled with their waste, and only tunnel their way out when they are leaving to enter the pupa stage of their development. Often times, these fruit end up going to market without anyone realizing that the damage has been done. Consumers then discover the infestation when they see the rot inside the eggplant, or have a larva emerge.

These are difficult pests to control, since they do their work on the inside of their target food source. Experts recommend that good farm hygiene practices be maintained at all times, with an emphasis on destruction of waste and older crop supplies to eliminate food sources that might serve to attract large populations of the creatures. There are a number of insecticides that can be used to maintain some level of control over these pests, and they are also subject to predation by native wasps.

Potato Moth Caterpillar

Despite its name, the potato moth caterpillar is not as choosy as some might expect. In addition to potatoes, this pest also seeks out tomatoes, eggplant, and even tobacco. These larval creatures are borers, which makes detection difficult in many instances. They also attack these plants anywhere they find them, from the field to storage locations. They mine both fruit and leaves, and can cause massive financial loss due to the reduction of crop quality and the need to destroy plants.

How to Control Caterpillar Pest Infestation?

Obviously, many of these common pests can pose significant economic risks to agricultural crops, and some impact home gardens as well. Controlling their infestation can be difficult, and some losses are almost always expected. Still, it is important to minimize those economic deprivations as much as possible. The good news is that there are some commonly used strategies for managing the pests.

Cultural Techniques:

Farm hygiene and crop planting techniques require careful attention. Closely planted crops can impede spraying efforts by preventing chemicals from getting where they need to be. That can allow a portion of any pest population to survive, adapt to the treatment, and pass that resistance on to future generations. In addition, crops need to be regularly rotated, as that is one of the best ways to disrupt population carryover from one planting season to the next. If you can deprive a species of its preferred food source by planting something else, you effectively end that infestation. Weed control is also a must, to prevent populations from establishing themselves in the early period after planting begins.

Biological Methods:

The introduction of a caterpillars’ natural enemies can be a natural way to limit population as well. Many of these caterpillars serve as prey to wasps, beetles, and other predatory species. By implementing a program that is designed to conserve these natural predators, you can allow nature to do its part in protecting your crops.


When it comes to any insect infestation, it is only natural that the mind turns to chemical solutions like pesticides. After all, insecticides have been used for many years to eliminate many major pest problems. But the success of those efforts has resulted in problems in the past, and makes effective chemical control something that requires due diligence and careful strategic planning.

Obviously, chemicals must be selected with the preservation of beneficial species in mind. Moreover, different caterpillars have developed different levels of resistance to a wide variety of commercial pesticides. For growers, that can make the process of selecting and using the right chemicals for any given infestation a real challenge.

Relying on the Professionals

Professional pest control experts are often the best solution in these instances where heavy infestations need to be addressed in a safe and effective way. Integrated pest management systems must be used to limit species resistance to pesticides and avoid harming those species’ natural enemies. These techniques offer a strategic approach to limiting pest populations that preserves beneficial populations while proactively reducing pest problems to limit economic damage.

Real pest experts understand these techniques and can help you evaluate the extent of your pest problem, assess your best options, and determine the right course of action to limit the damage caterpillars are doing to your crops, garden, or home. They utilize a rational, scientific approach to pest management that will emphasize environmental protection in balance with your need to reduce economic losses and maintain the integrity of your crop yield.

Caterpillars are a widespread plant pest throughout Western Australia, and cause irreplaceable losses each year due to the destruction they bring. Effective monitoring, preemptive control strategies, and professional pest control services can provide you with the three-pronged strategy you need to ensure that your plants and crops are provided the protection they need to survive and thrive each