A green tree ant colony needs assessment when nests bring people into repeated contact with defending ants. Colonies in trees away from paths and work areas can often remain. They prey on other insects and build leaf nests. Photograph indoor ant trails separately; a garden nest does not identify every ant found in the kitchen.
TL;DR
- A green tree ant colony in a garden tree is a working predator. Leave it alone unless its nests sit where people need to be.
- The nest you can reach is usually an outpost. A grown colony can hold more than a hundred nests across several trees, so pulling one down rarely ends the problem.
- Defenders bite and spray formic acid. Look up before you prune, pick fruit or set up a ladder.
- The ants farm sap-sucking insects for honeydew. A nest tree gives up some sap in exchange for protection from worse pests.
- Ants inside the house are a separate job. Book Ant Control for the indoor trail and mention the tree colony in the same call.
How do you identify green tree ants?
Green tree ants are Oecophylla smaragdina, a tree-nesting ant also called the weaver ant. Look for green colouring on a slender, long-legged ant with large eyes. Workers come in two sizes. Majors grow to about 10 mm and minors to about 6 mm, while queens reach 25 mm. The majors are the ants you meet. They forage and defend, and the minors stay inside the nest with the brood. The surest sign is the nest itself: leaves bound together with larval silk.
The species occurs in northern Australia's tropical and subtropical environments. A 2009 genetic study described differences between Queensland and Northern Territory colonies. Identify the ants at your property before deciding how to manage them.
Green tree ant and weaver ant are two names for the same insect. If an ant is on the ground with no leaf nest overhead, look again before you assume it's a green tree ant.
What do green tree ant nests look like?
A green tree ant nest is a bundle of living leaves stitched together with silk from the colony's larvae. Workers pull leaf edges together and form living chains to cross gaps. Other workers then hold larvae against the seams so the silk binds the leaves. Finished nests can look like balls, tubes or loose clumps of leaves. Colonies build anywhere from shrubs a few centimetres off the ground up to about 10 metres in the canopy.
Most nests use fewer than 150 leaves and often fewer than 50. The largest in one study held up to 300. Nest size tells you little about the colony, because one colony spreads across many nests. A grown colony can hold more than a hundred nests over several trees and more than half a million workers. Its territory can cover up to 1,600 square metres. On a suburban street, one colony can take in trees on more than one property.
Some outer nests are described as defensive outposts. Removing one reachable nest may leave other parts of the colony intact.
What do green tree ants do for a garden?
Green tree ants are predators that patrol their trees for other insects, and growers have used them as pest control for centuries. Kurzgesagt's published research notes record their use as biological control in China since 304 AD and credit them with reducing more than 50 pest species. A 2006 study in Northern Territory mango orchards reported effective control of Jarvis's fruit fly by green tree ants. The same notes say workers patrol every part of their territory every 5 to 7 minutes by day.
They keep livestock too. Workers lap up sap and tend sap-sucking insects that produce sweet honeydew. In an Australian rainforest canopy study, most of these partnerships involved treehoppers and scale insects. The ants let their own insects stay and drive off most others.
Crop studies describe both benefits from predation and costs from sap-sucking insects associated with the ants. An orchard result does not establish the effect on a particular garden tree. Look at the tree's condition and where people need access.
How do you avoid green tree ant bites?
Spot the nests before you work near a tree, then keep your hands and face away from them. Green tree ants hold their territory against rival colonies and competing ant species. Defending workers bite, and majors squirt formic acid at their targets. Formic acid is corrosive to tissue.
A few habits keep contact down:
- Look up before you prune, pick fruit, hang washing under a tree or set up a ladder. Nests can sit anywhere from knee height to the canopy.
- Read the ants. Workers ready to fight stand high on their legs with their jaws open.
- Wear gloves and long sleeves when you prune a nest tree. Defending ants release an alarm pheromone and call others to the spot.
- Move play gear, outdoor seating and the clothesline out from under nest trees.
Take a slow look along the branches before you start. You can work around a nest you've already spotted.
When does a green tree ant colony need management?
A green tree ant colony needs management when its nests sit where people must regularly work, walk or play. Colonies in high canopy or in trees away from daily traffic can stay. The line gets crossed when you find:
- nests in a fruit tree you harvest often
- nests in a hedge or shrub you trim
- nests over a doorway, path, clothesline, carport or play area
- workers massing on verandas, railings or outdoor furniture beside a nest tree
- someone in the household getting bitten again and again
A reachable nest is usually one outpost among many. Queensland colonies mostly have one queen, and she lives near the top and centre of the territory. Pulling down a low nest removes some guards and leaves the colony running.
Territory also changes hands. A James Cook University study of colonies in a seasonal tropical climate found a few trees switched between two competing colonies once or twice a year. Over one six-month period, more than 50 trees changed possession. An emptied tree in green tree ant country may not stay empty for long. The right response depends on how much of the territory touches the parts of the property you use.
How is a garden colony different from ants inside the house?
Tree nests and indoor trails are different observations. Identify both before choosing treatment. An indoor trail should not be assigned to a garden colony from colour alone.
| Green tree ant colony | Indoor ant activity | |
|---|---|---|
| Where the nest is | Leaf nests in trees and shrubs | Hidden nests, often found late |
| What you see | Green ants on foliage and nearby structures | Small light-brown, dark-brown or black ants trailing to food |
| Worker size | Majors up to about 10 mm | Argentine ants, a common invasive species, about 2 to 3 mm |
| What draws them | Territory and honeydew insects | Food, warmth and moisture |
| First question | Do the nests sit where people work? | Where are the ants getting in, and where is the nest? |
Several ant species may forage inside homes. Their food sources and nest locations differ. Report the kitchen trail and the garden nests as separate observations until identification establishes whether they are connected.
Report indoor trails and garden nests when you call so the assessment covers both. Damaged timber needs a timber-pest assessment. Our guide to reading a termite inspection report explains what that inspection records.
What happens when you book Ant Control for green tree ants?
Insight Termite & Pest Solutions' Ant Control service starts with what you have seen at the property. For green tree ants, describe the nest locations and the areas people use beneath them. We check the pest signs and access before recommending the next step.
Cost follows the job. It depends on the pest, property, access, severity, treatment method and whether follow-up is needed. Our guide to pest control cost in Rockhampton covers those factors in more detail.
Brendan Bartley owns the business and works as a technician. Licensed technicians with 10+ years' experience. We're locally owned and operated in Rockhampton, and we cover Rockhampton, Gracemere and Central Queensland. Call 0490 304 848 or send an enquiry. Send the pest, suburb and urgency, and tell us where the nests are.