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5 Worst Tree Pests in New South Wales

New South Wales is Australia’s largest state economy, contributing more than $500 billion every year. Its population, which is about 8.1 million residents, consists of professionals from fields of retail trade, manufacturing, health care, and construction – to name a few. 

With its economy thriving, we can expect that people keep a busy and hectic life. If you are an NSW resident, it is okay to take a breather from time to time. At night, you can relax in your garden and appreciate its beauty and breeze.  

Investing in trees is a wise move. Aside from providing fresh air and shade, trees can enhance the aesthetic appeal of your outdoor space. With its foliage-rich branches and colourful flowers, passersby will undoubtedly be in awe. 

But like any other living thing, you should take care of trees’ well-being and growth. Destructive garden pests can be your number one enemy once they have infested your plants and trees. They can bring sickness to your trees, which may soon lead to their death. 

So for guidance, here are the five worst tree pests in New South Wales to look out for:

1. Myrtle Rust (Austropuccinia psidii)

Myrtle rust is a type of fungus that usually affects plants belonging to the Myrtaceae family. Common Myrtaceae species include Lilly pilly, eucalyptus, willow myrtle, tea tree, and paperbark. It starts as purple spots in leaves and turns yellow once the infestation ages. In extreme cases, spots enlarge and meet, causing leaves to twist and deform. 

NSW Experts detected the increase of myrtle rust in 2010, affecting bushland reserves, property gardens, and even parks and street plantings. It spreads by wind, animals, insects, water, and contaminated garden tools. Now, it has reached other states such as Victoria, Queensland, and Tasmania.   

How to Manage Myrtle Rust?

Follow these steps to contain the spread of myrtle rust:

  • Familiarise the signs of infestation of myrtle rust. 
  • If detected, keep other plants away from the affected area. 
  • Always disinfect cutting tools and garden equipment before and after use. 
  • Apply fungicide to kill spores. 
  • Prune infected parts or prepare to fell the tree

2. Fall Armyworm (Spodoptera frugiperda)

Fall armyworm is a newly detected insect pest in NSW, which comes from Queensland. The larvae stage of the moth is usually light green to brown with a darker head capsule. It grows from 3 to 4 centimetres and takes 23-27 days to complete its life cycle. 

Like caterpillars, the fall armyworm larvae munch leaves, creating holes and shreds to plants and trees. Too much foliage loss can make trees susceptible to stunting or sunscald

Moreover, a single moth lays about 100-200 eggs, so expect heavy infestation once they hatch and develop into larvae. 

How to Manage Fall Armyworm?

Follow these steps to contain the spread of fall armyworm:

  • Check out trees for insect eggs and remove them when detected.
  • Control weeds to minimise pest hosts.
  • If you want, purchase insect traps to prevent moths from laying eggs.
  • Release beneficial insects – such as Trichogramma wasps, lacewing, ladybugs and minute pirate bugs – to feed on eggs and larvae.

3. Yellow Crazy Ant (Anoplolepis gracilipes)

Based on the Global Invasive Species Database, the yellow crazy ant belongs to the top 100 of the world’s worst invasive species. In 2018, NSW authorities detected its presence in Lismore CBD and Terania Creek North of Lismore. Its ‘crazy name means that it moves frantically and changes direction frequently. 

Yellow crazy ant has about 4mm long golden-brown body and a darker brown abdomen. Its legs are relatively longer than other ant species. Instead of biting, it releases formic acid as a defence mechanism.

The ideal nesting grounds for this insect are woody debris, tree bases, and leaf litters. It feeds on seeds, fruits, worms, and even larger animals such as frogs and birds as long as its colony attacks in groups. Moreover, it also protects other garden pests such as aphids and scales from beetles in exchange for nectar or honeydew. 

How to Manage Yellow Crazy Ant?

  • Inspect tree bases and garden debris of unusual ants or nests.
  • If possible, use a broad-spectrum insecticide like Fipronil.
  • Discard green waste appropriately.  
  • Call professional gardeners whenever in doubt.

4. Pampas Grass (Cortaderia selloana)

Pampas grass is a common weed mostly found in Tasmania, NSW. Before being classified as a noxious weed, garden owners used it as windbreakers or soil stabilisers. But since it spreads quickly, it has become a threat to parks, roadsides, and even residential gardens.

It is a perennial plant that can grow up to 4m in height. In general, it forms large clumps of lush, grass-like foliage and brownish-white feathery plumes. Once established, it is highly competitive for water and nutrients, restricting the growth of nearby trees. Furthermore, it is a fire hazard and attracts pests or nuisance animals that spread tree and plant diseases.   

How to Manage Pampas Grass?

  • In small infestations, plant grubbing can prevent further weed growth. 
  • Apply herbicides but remember to follow NSW regulations. 
  • Hire a local garden maintenance provider like Trees Down Under.

5. Giant Willow Aphid (Tuberolachnus salignus)

The giant willow aphid is an established plant pest in NSW that clusters in branches of willow trees. It is a mid to dark-brown insect, known for its row of black spots in its abdomen. Adult species grow about 5-6mm long with a relatively short antenna, just half the body length. 

As mentioned, its colony usually crowds branches of willow trees. It sucks saps from the host and releases sweet honeydew, which attracts other insects and pests. Signs of infestation include black sooty mould on twigs and deformed leaves. Both honeydew and sooty moulds interfere with photosynthesis, impeding the trees’ growth and health. 

How to Manage Giant Willow Aphid?

  • Once present, use water pressure to knock them off from the branches. 
  • In cases of heavy infestation, use insecticidal soap or horticultural oil to kill them. 
  • Scrape and remove clusters of eggs in branches or twigs.
  • Use an ant control product to prevent ants from protecting themselves from beneficial insects. 


Trees are a great addition to your backyard – especially here in New South Wales, where fresh air is limited. Aside from providing essential tree care, garden pest prevention is crucial for their healthy and vigorous growth.

Always lookout for the mentioned five worst tree pests here in NSW. And when in doubt, you can rely on the best and the brightest garden service provider in Sydney, Trees Down Under! 

Most Trusted Garden Service Provider in Sydney

Trees Down Under has professional and skilled gardeners and arborists who can effortlessly spot garden pests and remove them right away. We provide tree care services such as trimming, pruning, and removal to maintain the beauty of your garden in the best way possible. 

We equipped ourselves with the appropriate tools and devices to bring safe, efficient, and excellent garden services. Expect us to be at your doorsteps at your most convenient time. Our team is available 24/7 to answer your tree and plant concerns. You can receive your free quote when you book with us. Contact us at 0475 463 597 or send us a message through our email.

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