25 Most Destructive Garden Pests

Most garden owners dream of their outdoor space with the right mix and style of flowers, shrubs, crops, and trees. Aside from considering their desired plants, they need to give tender, love, and care to each of them for healthy and desirable growth. Plants require water and fertilisers for nutrients and the right type of soil and sunlight for proper development. Moreover, they also need trimming and pruning for maintenance and disease prevention. 

Pests are one of the worries of garden owners. Sometimes, they don’t even know that pests have already infested their plants since most of these unwanted guests spread fast, and are invisible to the naked eyes. 

So that you can understand better, here are the 25 most destructive garden pests that can cause harm to your backyard plants:

1. Earwigs

Earwigs are brown six-legged insects. They have two antennae, three body divisions, and a pair of forceps on their rear. Depending on the species type, they can grow from 5mm to 25mm. The common misconception about earwigs is that they crawl up then enter one’s ear and eat up brains. Please note that they are harmless to humans. But they can become troublesome pests once they set foot into gardens. 

Depending on their numbers, earwigs can be pests or not. A small population of earwigs can hunt other pests and eat decaying plant matter. But most of the time, they come in large numbers and wipe out seedlings, fruits, vegetables, and ornamental plants. 

How to spot earwigs

Earwigs tend to live in a humid and moist environment. They are often under piles of wet leaves, lawn clippings, mulch, and damaged fruits. They are active at night and attracted to lights. During dry periods, they may wander inside the house, especially in the kitchen and basement.

How to get rid of earwigs

• Set up oil pit traps.
• Spread out petroleum jelly on plant stems.
• Sprinkle borax on infested woodpiles.
• Make an insecticidal spray with ratio 1:1.5 of 70% rubbing alcohol and water, respectively.
• Put a ring of diatomaceous earth (DE) on the bases of plants.

2. Curl Grubs

Curl grubs are the larvae of different species of beetles such as African Black Beetle and Christmas Beetle. They have a white or pale cream body, brown head, and greyish end. As their name implies, they have a habit of curling and form “C” most of the time. And they can grow about 2.5cm long.  

Adult beetles lay their eggs in garden soils. As soon as the larvae hatch, they feed on roots and affect the lawn. Curl grub infestation makes the plants demand more water or kill the plants in case of an outbreak. 

How to spot curl grubs

Curl grubs attack on a wide range of plants except for legumes. During warmer days, the new eggs hatch and the older larvae move closer to the surface while feeding heavily on roots. Brown and large dead patches on the lawn are signs of infestation. Moreover, potted plants are more vulnerable as they have limited space for roots. 

How to get rid of curl grubs

• If exposed, pick them up and feed them to birds.
• Apply organic insecticides during mid-spring to mid-summer to kill hatching eggs and approaching larvae. 
• Minimise outdoor lighting to prevent attracting beetles at night. 

3. Wireworms

Wireworms are one of the most common garden pests in Australia. There are 667 species of true wireworms in the country, mostly spread in cane fields of north, central, and south of Queensland, and New South Wales. They are the first stage of click beetles. Most wireworm larvae have a hard-like body structure, brown, and varying from 13mm to 38mm in length. But some species are also soft and white or yellowish. 

Wireworm usually causes damage at the start of plant development. In particular, they are destructive to corn. But crops such as potatoes, beans, and cabbage are also typical victims. Furthermore, they can also cut small roots or tunnel into the underground portions of the root system.  

How to spot wireworms

Wireworm infestation occurs in moist areas. They require 2 to 6 years in the soil. In those times, they eat on the roots of grasses and plants to complete development. During the dry season, they are hard to locate. They move downward because moisture is barely present on the surface. Moreover, if heavy infestation happens, thin and patchy crops are signs of wireworms in the garden.  

How to get rid of wireworms

• Put soil insecticides, especially if planting corn.
• Control grassy weeds.
• Practice crop rotation to promote soil development and prevent infestation.
• If there are no other choices, make a soil drench with pyrethrin, a biological insecticide. 

4. Root Maggots

Root maggots are the larvae of several species of root maggot flies. They are usually white and about 7mm long. Most of their garden victims are root vegetables and crops such as carrots, turnips, cabbage, and broccoli. 

How to spot root maggots

Root maggots are challenging to spot unless they already cause damages such as holes or tunnels in the roots. Moreover, if the plant itself wilt or turn yellow, root maggots are most likely the culprits. During these circumstances, lift the plants from the soil gently and check for root maggots. 

How to get rid of root maggots

• Spread diatomaceous earth while the plants are still seedlings.
• Apply pesticides for root maggot control. 
• Practice crop rotation and remove dead vegetation during fall. 
• If infestation currently occurs, cut back on the use of organic materials, specifically manure.

5. Tomato Hornworms

Tomato hornworms are green caterpillars, characterised by V-shaped markings on their abdomen. They can grow from 7cm to 10cm with a slender pointed tip on their tails. They usually cause damage by feeding on leaves and chewing holes on fruits. Too much foliage loss may result in stunting and sunscald. 

How to spot tomato hornworms

Tomato hornworms are dangerous when they are large in numbers. Due to their green colour, they can camouflage well on stems and the foliage. It is best to check the leaves for holes and shreds. Furthermore, they release green substances when they eat. So it is also crucial to check on other plant parts and the ground. 

How to get rid of tomato hornworms

• Pick them up and squash them together on a cloth or drop them in soapy water. 
• If uncontrolled, a natural pest control, Bacillus thuringiensis, can solve the problem.  

6. Scales

Scales are sap-sucking insects that attach themselves to branches, twigs, leaves, and fruits of plants. They are tiny, brown, and oval creatures that are capable of multiplying at a fast rate. They most likely enter into gardens when the temperature is warm and dry. Scales are dangerous as they can suck out nutrients from the plants, affecting their growth and development.  

How to spot scales

Most garden owners identify scales as a disease rather than a pest. But they are not. Honeydews and white powders on the leaves and stems are signs of scale infestation. Furthermore, when the foliage turns yellow and leaves keep on falling, scales may have already multiplied.   

How to get rid of scales

• If there are only a few of them, pick them out and put them on a cloth. 
• Prune affected parts and avoid them from making contact with healthy plants. 
• Gently press a cloth soaked in alcohol to the affected area. 
• Apply neem oil pesticide when necessary.

7. Rosemary Beetles

Don’t be fooled by their beautiful appearance. Rosemary beetles are destructive pests, especially for aromatic herbs such as rosemary, lavender, and thyme. They are shiny insects with metallic green backs and purple-bronze stripes. They can grow between 6-8mm long and more active in late spring and late summer. 

How to spot Rosemary beetles

Rosemary beetles often feed on tender tips of herb stems that usually produce a high concentration of camphor. It causes leaves to develop brown and withered edges that distort the growth of affected plants. Always check the underneath of leaves as that’s the spot where they usually lay their eggs. 

How to get rid of Rosemary beetles

• Look for their eggs and get rid of them using soapy water.
• If possible, shake Rosemary beetles off from plants and pick them up. Then, drown them in soapy water.
• Prune damaged branches and twigs.
• As a last resort, use Pyrethrum-based products to get rid of them. 

8. Leaf Miners

Leaf miners are the larvae of various insects that feed on upper and lower surfaces of leaves. They appear like worm maggots that are 9mm long with pale yellow or green colour. As their name suggests, they attack mostly on leaves and reduce yields and vigour in most plants. Beans, peppers, ornamental flowers, and citrus trees and shrubs are the most common victims of these destructive garden pests.  

How to spot leaf miners

Leaf miners usually leave traces of white or light green lines on leaves’ surfaces. Sometimes, there can be black stripes at the tunnel edges. On heavily infested plants, there could be 6 or more leaf miner species on a single leaf. They can cause leaves to turn yellow and fall if not remedied immediately. 

How to get rid of leaf miners

• Examine leaves for white or light green marking lines.
• Maintain plant health with organic fertilisers and proper watering to prevent leaf miner infestation.
• Use floating row covers to avoid insects from laying eggs on leaves. 
• Apply botanical insecticides as a last resort. 

9. Mealybugs

Mealybugs are destructive pests that suck saps from leaves and stems. They are about 3-7mm long, covered in a layer of white powder. They multiply quickly, which makes them hard to control once they become an outbreak in gardens. Different species prefer different feeding areas. Some suck saps under trunks, while others usually attack fruits, flowers, and seed heads.  

How to spot mealybugs

Mealybugs usually excrete honeydew on leaves and stems, so they are easy to spot. They develop in humid condition and peak their numbers during spring and autumn. Symptoms of mealybug infestation include yellowing of leaves, foliage loss, stunting, and wilting.  

How to get rid of mealybugs

• Scrap them off manually with a stick.
• Prune affected plant parts.
• Spray with a veggie oil-soap mixture to get rid of them.
• Use parasitics wasps and Ladybirds to feed on mealybugs.

10. Cutworms

Cutworms are caterpillars of several moth species. They have a plump and smooth-like appearance, and they can grow up to 40mm long. Depending on the type of species, they can be dark grey or light pink in colour. Cutworms can make sharp cuts on stems that may result in their death if ignored.  They feed on a wide variety of plants such as lawn grasses, vegetables, and ornamental flowers. 

How to spot cutworms

If there are scissor cuts on the base of the plants’ stems, cutworms are most likely the culprits. They are tough to see as they usually hide under soil or littered items. Furthermore, they are also prone to stay near the surface of damaged plants. 

How to get rid of cutworms

• Watch out for disappearing seedlings at the early stage of plants.
• Avoid pest infestation with proper garden maintenance and care. 
• Use organic pesticides as much as possible. 
• If there are no other options, go for synthetic pesticides, but be wary of their effects. 

11. Psyllids

Psyllids are insects with six legs, two thread-like antennae, and a pair of brown-marked wings. They are commonly known as plant lice due to their tiny size that varies from 2.5mm to 5mm. Like any other sap-sucking insects, they steal the nutrients of host plants and hinder their development.  They usually attack native Australian plants such as lilly pillies, wattles, and eucalypts. 

How to spot psyllids

When there are ants and bugs on plants feeding on a sticky substance called honeydew, psyllids are most likely the root cause. Psyllid infestation also results in foliage loss, leaf discolouration, and mould growth. Outbreaks typically occur during early spring and mid-autumn. 

How to get rid of psyllids

• Pruning affected plant parts can help, but not effective in the long run. 
• Applying neem oil in affected segments is more effective. 
• When there are no other options, use insecticides.  

12. Weevils

Weevils are beetles that are famous for their elongated snouts. In general, their colours are dark brown to black, and they can grow up to 6mm long with slender and oval-shaped bodies. These destructive little insects can conquer the root system of a healthy plant and eat their way up. Aside from outdoors, they can also infest indoor food such as rice and cereals. 

How to spot weevils

Weevil eggs are hard to locate. And as they mature, they tend to move from outdoor to indoor. You can often find them near food storage or crawling on the walls or windows. They usually invade homes during fall and summer for shelter. On the other hand, they love to eat at night, leaving bite marks on leaf edges and roots. 

How to get rid of weevils

• It is best to pick them out at night. 
• As they are attracted to moisture, set up a pan of shallow water outside as bait.
• Release parasitic beetles that can hunt down weevils.
• Apply pesticides to leaves or soak the soil with liquid pesticide.
• Clean up dead plants and avoid too much mulching. 

13. Cabbage Loopers

Cabbage loopers are one type of caterpillars that are common as garden pests. As their name suggests, they mostly eat cabbages. But, they also feed on lettuce, kale, and other vegetables. They are about 5cm long, with green bodies and silver or white stripes. 

How to spot cabbage loppers

Cabbage loopers typically hide underneath leaves, and due to their colour, they are hard to spot. Also, don’t underestimate them even if they are slow movers. They have big appetites that make holes in the leaves of plants. Too much foliage attracts diseases and may soon cause death.  

How to get rid of cabbage loopers

• Manually handpick them and drop them in soapy water.
• Use row covers during spring to prevent butterflies from laying eggs.
• Planting flowers such as marigolds and sunflowers attract insects that can kill cabbage loopers.
• Use insecticides or insecticidal soaps during a heavy infestation, moderately.  

14. Flea Beetles

Flea beetles are garden pests that endanger many vegetable crops such as turnips, potatoes, spinach and melons. They are small, yet destructive creatures as they chew irregular holes on leaves and result in plant stunting and wilting. 

Most adult flea beetles are 1.5mm to 3mm long, distinguished by their spots and patterns. Also, depending on their species, they can be black, bronze, bluish, or grey. Moreover, they have large back legs that are ideal for jumping, especially when disturbed. 

How to spot flea beetles

Flea beetles are active during spring, but they can also survive the cold months of winter. They hide on leaf litter, hedging plant rows, windbreaks, and wooded areas. Female flea beetles usually lay their eggs on soils and leaves of plants, and occasionally on flowers and trees.

How to get rid of flea beetles

• Check holes on leaves for possible infestation.
• Control weeds to limit food sources of flea beetles. 
• Protect plants with mulch covers.
• Applying neem oil is a temporary solution to get rid of them.
• Use pesticides with spinosad or permethrin agents. 

15. Thrips

Characterised by their small size and flat shape, thrips are dangerous since they require a magnifying glass for detection. They can be 1.5mm to 3mm long, with various possible body colours (brown, black, yellow). Moreover, they carry viruses, mainly of the genus Tospovirus that causes significant crop loss. 

How to spot thrips

After feeding on garden plants and crops, thrips leave white patches, mostly visible on leaves. It is also their way of spreading the viruses they carry. Other signs of infestation include bacterial leaf streaks and silvery specklings. 

How to get rid of thrips

• Place a cloth underneath an infested plant and shake the branches to remove thrips. 
• Spray neem oil and insecticidal cleansers. 
• Pruning affected areas are helpful as well. 
• Dust the underneath of leaves with diatomaceous earth. 

16. Bagworm Moths

Bagworm moths are harmless to humans but can become nuisance pests in gardens. They are about 3cm long and colour brown to grey with patterns on their wings. However, female bagworm moths don’t have wings and legs, which makes them appear like worms. 

In general, they feed on evergreen and deciduous trees and shrubs. Severe infestation causes defoliation, especially on juniper and arborvitae trees.  

How to spot bagworm moths

Bagworm moths usually make trees their shelter. Meaning, they also incline to lay their eggs on backyard trees. As soon as these eggs become larvae, they crawl to surrounding plants and leave their bags on the hosts. Some species also produce silk threads. Furthermore, severe defoliation is also a sign of infestation, as mentioned earlier. 

How to get rid of bagworm moths

• Handpick bagworm moths and put them on soapy water or seal them in bags. 
• Remove green waste and dead branches in the lawn. 
• Apply insecticides to areas with their larvae. 

17. Spider Mites

Spider mites are not insects but arachnids. They are pale or reddish-brown, oval-shaped, and about 0.5mm long. Moreover, they have two dark spots on each side of their body. Mites live in colonies and attack almost all kinds of plants. They pierce leaf tissues and suck fluids for nutrients. 

How to spot spider mites

Spider mites most likely survive in hot and dry conditions. They also come in large numbers. So once they have infested gardens, plant owners need immediate solutions. As mentioned, they usually stick to the undersides of leaves. Furthermore, leaf discolouration and dropping, and fine webbing are signs of spider mites outbreak. 

How to get rid of spider mites

• Prune leaves, stems, and other infected plant parts. 
• Use a bug blaster that maximises a high pressure of water to remove spider mites. 
• Apply horticultural oil on fruit trees in early or late fall to kill their eggs.
• Spray biological or commercial insecticide as a last resort. 

18. Whiteflies

Whiteflies are small sap-sucking insects with two pairs of rounded wings covered with a white waxy powder. They grow up to 1.5mm long and are often near the top of the leaves and end of stems. Moreover, they are active during the day and will fly out when disturbed. 

They like to sap nutrients from trees and eat on leaves. Ornamental flowers and warm-weather vegetables are the usual victims of whitefly infestation. 

How to spot whiteflies

As whiteflies suck on plant juices, they cause leaf discolouration, and in severe cases, leaf drop. Moreover, sooty mould grows on the honeydew, leaving black marks on the leaves. Whiteflies are more visible in mid to late summer as the condition is humid and warm.  

How to get rid of whiteflies

• They prefer newly unfurled leaves, so check on them first. 
• Blast whiteflies with a water hose or spray, strong enough to get rid of them. 
• Consider spraying leaves with insecticidal soap.
• Use commercial insecticides when all else fails.  

19. Aphids

Aphids are small white bugs that are one of the most common destructive pests in gardens. They are about 6mm long with a pear-shaped body and a pair of long antennae. Most garden owners worry about aphids as they multiply fast and survive any weather conditions. 

They can attack various kinds of plants, but prefer beans, potatoes, and other vegetable crops. Moreover, they infect almost all parts of trees, shrubs, and plants, depending on the type of species. 

How to spot aphids

Dull or changed colour of leaves may mean aphids already infested the plants in question. Turning leaves over can verify if they are present. Moreover, sticky substance on stems or other parts can be a residue left by aphids. Check for honeydews on plants and the ground, or look if other insects are feasting on them. Furthermore, honeydews promote fungal infection, so it is best to get rid of aphids as soon as possible. 

How to get rid of aphids

• Spray cold water on infected leaves or apply a water pressure for better results. 
• Pour flour on plants to reduce pests’ footing.
• Place garlic near ornamentals, shrubs, and trees to repel aphids.
• Mix a litre of water, a teaspoon of dish soap, and a pinch of cayenne powder. Then, spray them on infected leaves. 
• Check this article on how to prevent aphid growth in your orchard.

20. Japanese Beetles

Japanese beetles are about 100mm long with metallic green bodies and brown wing covers. They are also one of the most common garden pests as they eat almost everything on plants. They usually feed in groups starting at the top and work on their way down. 

How to spot Japanese beetles

Japanese beetles appear on warm and sunny days. They also prefer plants located in direct sunlight. Group feeding results in foliage loss and most trees appear like victims of scorch fires. Furthermore, they like to consume rose petals and leaves with delicate veins. 

How to get rid of Japanese beetles

• Use mulch covers during the peak season of Japanese beetles.
• Spray castor oil soap as a remedy.
• Treat soil with Bacillus thuringiensis to prevent infestation.

21. Slugs

Slugs are soft-bodied molluscs. But, unlike snails, they don’t have hard shells on their back. Most slugs are grey, dark-orange, and brown, and they grow from 2cm to 8cm long. Even though they are slow movers, they are capable of wiping out an entire crop in a matter of days. They like to eat vegetable-producing plants and also attack most leaves and seedlings.   

How to spot slugs

Slugs usually hide in moist areas such as under rocks, mulch, heaps, and pots. Furthermore, they are more active at night and wander the garden when light is low. Holes in fruits and leaves are signs of slug infestation. 

How to get rid of slugs

• If you want, invite slug predators such as chicken and ducks in your garden. 
• Spray beer or alcohol to kill them.
• Block them with sand, copper wire, or tapes. 
• Trim long grasses and weeds as these invite slugs.

22. Possums

Possums are one of the most common marsupials native to Australia. They are highly adapted to living near humans, so they don’t have a problem visiting residential gardens. They feed on leaves, flowers, buds, and fruits. If ignored, they can infiltrate in large numbers and damage outdoor spaces.  

How to spot possums

Possums are nocturnal. They tend to visit at night, rummaging garden plants and garbage bins. It is best to shoo them before they multiply and invite other companions. 

How to get rid of possums

• Use possum repellents or activate an automated water sprinkling system to startle them. 
• Set traps, but don’t kill them as they are under a protective program. 
• Build fences as a defence. 
• Check this article on how to make a possum proof garden. 

23. Grasshoppers

Grasshoppers are green insects, known for their leaping ability. They have robust bodies and relatively short antennae. As they are light and fast, they are hard to catch. Grasshoppers usually defoliate everything in sight but prefer young green plants. 

How to spot grasshoppers

Vegetables and crops such as beans, corns, and carrots are the usual victims of grasshoppers. Meanwhile, squash and tomatoes are their least favourite. Grasshopper infestation usually happens in the starting weeks of summer right after weeds dry up. Their marks are pretty evident as they leave large bites on leaves and flowers. 

How to get rid of grasshoppers

• When numbers are low, handpick grasshoppers and squash them.
• Put floating row covers for protection.
• Apply hot pepper wax spray, which is available in the market. 

24. Fire Ants

Fire ants are not only dangerous to plants but humans as well. If bothered, they inflict painful bites and stings. With their darkish-brown appearance and tiny size, they are usually hard to spot in the garden. They can damage vegetable crops such as potatoes and okra, and eat up seedlings of corn and cucumber.  

How to spot fire ants

Presence of mounds is enough evidence for their existence. Moreover, they tend to move as a group, climbing on trees and plants. Also, when there is sugar, ants will most likely show up. It is essential to check for fire ants to avoid stings when tending on trees, shrubs, or ornamentals. 

How to get rid of fire ants

• Set up a fire ant bait containing methoprene or spinosad as an active ingredient.
• Use liquid drench to eliminate their mounds in the garden. 
• Apply granular insecticides before planting. 

25. Rodents

Aside from insects, creatures like rodents pose a threat to your backyard. As rodents look for food, water, and shelter, gardens are an ideal spot for their survival. They can colonise compost pits, ornamentals, and vegetations. If ignored, they may soon infiltrate houses. 

How to spot rodents

Rodents often dig up tunnels on soil with a small entrance and exit hole. These are their passageway to feed on their food, possibly crops in the garden. They also create mounds to mark their burrows. One noticeable sign of rodents is their excrement that looks like black grains of rice.

How to get rid of rodents

• Remove mounds to shoo rodents away. 
• Eliminate grubs to uninvite rodents into the garden. 
• Make sure to clean and sanitise the outdoors.
• Seal holes that can be their possible entrance.
• Build fences, especially for plants that require essential care.  

Conclusion

If you are a garden owner or a caretaker, you need to make sure that your plants receive the utmost care if you want them to grow healthy and strong. One effective way to do that is by preventing garden pest infestations. With the 25 most destructive garden pests presented here and their corresponding cure and prevention, the responsibility now lies in your hands. And if you need expert care and advice, Trees Down Under is 24/7 on alert to give bespoke and quality garden services. 

Our team of professional and reliable gardeners offer plant and tree treatments to avoid pest infestations. Your garden is in good hands as we make sure that the products we use don’t interfere with your plants’ growth and development. Aside from treatments, we also conduct trimming, pruning, and mulching services for the well-being and safety of your backyard space. 

Since 2005, we are providing bespoke yet affordable residential tree services , commercial tree services, and industrial tree services in Sydney. We are the number one tree and garden service provider no matter where you are in Sydney. After your call, we will make sure to dispatch the best and brightest team, fully geared up with the right tools and protective equipment. 

So, solve your garden pest problems with Trees Down Under now! Contact us at 0475 463 597, or send us a message through email.