Tree Bugs and How to Fight Them

We are blessed here in New Zealand not to have all that many destructive, environment-destroying bugs. Biosecurity New Zealand, with our help, is doing all it can to keep it that way. However, that’s not to say we’re pest-free and that our pest management is already at its peak. 

We’ve got a significant gorse problem, and possums are eating all our fruit. We also have many different tree bugs that don’t seem to want to play nice. If you find yourself with vulnerable trees thanks to the local bug population, then read on. Below, we identify some of the more common tree bugs and insects – pests in New Zealand – and how to fight them.


Millipedes, in the scheme of things, aren’t as much of a major threat as what other countries are facing. However, they can take a fancy to your young seedlings, which can be devastating if you treat your plants like your children. 


Millipedes eat leaves, roots, and stems. They’re also carnivorous, feeding on spiders and insects that cross their path and look slightly delicious. One or two millipedes in your garden are no problem at all, but too many of them can be a pain.

 Fortunately, you don’t have to reach for the chemicals to give these multi-legged creatures their marching orders. Because millipedes love moist environments, you merely have to take away what they love the most. 

Identify where your millipede population is gathering. What’s there that the bugs would like? Any decaying plant matter, rotting wood, rotting leaves, or similar, is like a candy store for a millipede. Take care of the material yourself, or ask for a helping hand. Those pesky critters will be gone in no time. 

Scale Insects

If your hydrangea leaves have strange-looking blobs on them that are white in colour, then you most likely have cottony hydrangea scale bugs. Those white blobs you are looking at are egg mass! 

Scale insects hatch in mid-summer and suck the sap from the underside of your hydrangea tree’s leaves. At the end of summer, they’ll then run out of leaf sap and move onto the stems. While the occasional infestation is possibly something your tree can take in its stride, multiple attacks can weaken it. 

The next time you’re hanging out the washing, trimming trees, or mowing the lawns, wander over to your hydrangeas and inspect the leaves. If you see those dreaded masses, pick off the leaves and put them in your wheelie bin. 

If you want a more permanent solution for this type of pest control, then you can use a pyrethrum-based spray with newly-hatched scale bugs from midsummer.


Citrus Tree Borer


The name of the citrus tree borer can be deceiving. You might think you’re safe from it because it only attacks citrus trees, but this little critter doesn’t discriminate. Instead, it’s a beetle whose larvae will bore into any garden tree or shrub it takes a fancy to if it can’t find its favourite warm home – the lemon tree.

The borer can cause significant damage, taking you unawares. Adult borer will lay eggs in cut or damaged tree bark; then the larvae will bore into the living wood. They will then create holes to get rid of their frass (a nice name for waste). If you don’t take care of citrus tree borer, it can eventually make your tree its victim – killing it. 

 Take action immediately by pruning the affected limbs. You can also call an expert for help. Clean away the dead branches and leaf litter then purchase a borer injector fluid to inject into the waste holes the borer create. Once you kill the larvae, you can fill the holes with a Blu-Tack-type product. 

Native Moth Caterpillars

If you thought standard cabbage moths were a problem, then you haven’t seen what the native species of moth caterpillar is capable of! The caterpillars of native moths don’t have many predators. As it turns out, they aren’t that appetising to other insects.

As a result, they can create a lot of carnage in a short time without anything else standing in their way. Their favourite victim is the cabbage tree. They form deep notches in every leaf they can find, not stopping until the cabbage tree is a mere shell of its former self. 

There are various products you can buy to take care of these creatures, but you can also try home methods as well. Mix two cups of water with two teaspoons of garlic powder and one of dish soap. Spray the mixture onto the cabbage tree leaves, and you’ve (hopefully) seen the last of them.

Tony Wills ( CC BY-SA 4.0 )

Tony Wills (CC BY-SA 4.0)

Bronze Beetle


Bronze beetles are tree bugs that you want to take care of while your trees are young. Otherwise, they are a “take no prisoner” bug that can ravage a tree in no time at all. They are only small, at around four millimetres, but love leaves, apples trees, and rose flowers. 

They create substantial leaf scars, take big bites out of your apples, and shred your beautiful rose petals until they’re in tatters. When your trees or plants are young, you can shake them off the leaves into a container. Otherwise, you may need to try a spray from your local garden store.


We have many introduced and native tree bugs and pest species that like to make their mark on our native ecosystems. Take back control by taking preventative steps and investing in quality tree care products or experts. These will help give them their marching orders sooner rather than later.

Zach White