Frequently Asked Questions

What bug is eating my Elm tree ?

Beetle Eggs | Elm Leaf Beetle | Larvae
Beetle Eggs | Elm Leaf Beetle | Larvae

If you have damage to the leaves of an Elm tree in south eastern Australia, particularly Melbourne or Victoria, it is most likely to be Elm Leaf Beetle Damage. If whole leaf sections are being eaten that is usually possum damage.

Elm Beetles eat holes while the larvae skeletonize the leaf leaving the veins and a thin film.

What are these green beetles leaving yellow stains on my walls and curtains?

Elm Beetle and eggs
Elm Beetle and eggs

Elm leaf beetles will spend the cooler months in sheltered places like house eaves and wood piles, if they have access to house interiors they can leave nasty little yellow stains.

What does an Elm Leaf Beetle look like?

See images opposite.

The Elm leaf Beetle is small, around 4mm long, dark brown / green with two lighter green GT Stripes down its back.

What do Elm Leaf Beetle eggs look like?

The eggs of the beetles are laid on the underside of the leaf in late November and look like two rows of bright yellow dollops from a VERY small piping bag.

They hatch after about 8 days and the first incarnation of larvae crawl about initiating leaf damage.

Does my tree have Dutch Elm Disease?

We do not have Dutch Elm Disease (DED) in Australia…….yet, which is why we have the largest surviving population of European Elms in the world. We do have Elm Bark Beetle which is the vector for DED.

Elm tree problems – other

Elm Leaf Possum Damage
This type of Elm Leaf damage is usually due to Possum predation rather than Elm Leaf Beetle.

There are other problems associated with elms including the bacterial disease Slime Flux, this disease results in a brown slimy ooze that runs down and stains the trunk or larger branches. Slime flux is not considered a significant problem in Elm trees and there is currently no satisfactory treatment. Elms in Melbourne are also susceptible to Possum predation – see image opposite.

How do I stop Elm Leaf Beetles eating my tree?

Treetec provides a range of treatments, email or phone us 03 8644 8005.

There are a range of Elm Leaf Beetle controls but no permanent solution at this point, the best success is with chemical treatments though there are some organic measures that can help reduce Elm Beetle numbers.

We will soon be starting an experiment with a duck, ducks love grubs and beetles and this would be the equivalent of trunk banding, we’ll keep this space updated and if anyone has information on this or other types of organic controls please let us know.

Why are my Elm tree leaves skeletonized?

Elm leaf treatment larvae damage
The larger holes are from the adult Elm Beetle while the larvae have started stripping the area between the leaf veins

The stripping of Elm tree leaves is from Elm Leaf Beetle larvae rather than the parent beetle. (see image)

What Elm Leaf Beetle chemicals / insecticides are commonly used ?

predominantly the active ingredient used is Imidacloprid you’ll find it in Confidor and other brand names and even in your dog’s flea collar. The chemical is sold and used in different formulations depending on the mode of delivery.

These chemicals are nearly exclusively neonicotinoid insecticides which have been linked to the decline in bee populations across Europe.

Why should I use a qualified arborist to work on my Elm tree?

Because we are consulting arborists and ecologists at Treetec we have an understanding of trees and tree care, we can help give a broader perspective on both the health and structure (safety) of your trees and consult on the longer term implications of your Beetle treatment decisions.

For example we can provide some unbiased guidance on tree structure / failure potential and the associated risk of a failure as well as the implications of drilling or injecting trees or using soil treatments.

How often should I treat my tree for Elm Leaf Beetle?

At Treetec we suggest a stem or soil treatment every three years, in some instances the treatment will last longer particularly if your tree is isolated from other trees with Elm Beetle infestations.

In the third year we often see a small increase in damage however it is normally at manageable / acceptable levels. If it is left much longer the Elm Beetle population can increase dramatically.

If you are comfortable with some damage in some years we encourage people to try trunk banding in the third and even a fourth year to try and reduce chemical use. This approach can leave your tree looking less than perfect in the fourth year (or even fifth) however moderate damage to a tree every so often will not kill it.

Elm tree treatment soil injector
Soil injection treatment for Elm tree damage uses a small probe to deliver the treatment directly to the root zone.

When is the best time to apply Elm Leaf Beetle treatments?

This depends on the treatment used, for soil injection ideally the treatment is done just before or as trees come into leaf, it can be later however there is likely to be some leaf damage if it is left too late in the season.

Stem injection for Elm beetle can be done any time the tree is in leaf, take-up is relatively fast. Some injectors are so powerful they can get chemical into the trunk any time of year regardless of how much transpiration (water movement) is going on. We believe this is poor practice as it damages plant tissue near the wound site and is not necessary, a slower more controlled dose during spring is better for the tree.

Foliar spray for Elm leaf eating insects can be done any time when in leaf but ideally it should be either when all beetles have emerged onto the tree but have not laid the eggs or as soon as possible after the eggs hatch.

Drought Stress
Elm tree treatments will avoid this type of leaf damage. Late in the season larvae damaged leaves will turn brown, curl and fall.
Larvae damage combined with hot dry conditions can quickly defoliate much of a tree.

What if my neighbour has Elm Leaf Beetle and doesn’t treat their tree?

Elm beetles are much better at hitch-hiking than flying, or possibly they are bone lazy, or they are smarter than the average Beetle! Either way most of thier movement across eastern Australia is by road not air. If your trees are isolated from other Elm trees your tree/s will be re-infested more slowly. Don’t park under infested Elm trees in summer!

Neighbouring trees will see some crossover of flying Elm Leaf beetles however if your tree is properly treated it will still look very good even if your neighbour doesn’t treat their tree. Often it is the Elm beetle larvae that do the most significant damage and they neither fly nor hitchhike (despite their obvious enthusiasm and energy).

We have seen, inside a house, some serious staining of internal walls and fabrics from the beetles of a neighbour’s tree, this happens prior to them emerging from where they overwinter.

Legally if the trunk meets the ground within your property then you own the tree and there is some precedent in the courts that means if you own a tree you are responsible for all parts of the tree: leaves, fruit, roots and possibly even the beetles however we are unaware of the beetle bit having been tested in the courts.

What organic controls are there for Elm Leaf Beetle damage?

The beetle is an insect so any home brew or organic recipe (pyrethrum) that you can spray onto them may help, the main organic control method for Elm Leaf Beetle is trunk banding and this can be done with or without chemicals.

There are banding options with gells such as ‘Tree Guard’ from GoNatural.

Trunk Wrapping
Tape sticky side out trapping the Beetle larvae as they head to the ground to pupate.
Some larvae don’t bother with the trunk, they go with gravity thereby avoiding trunk banding traps.

State government research has been undertaken on parasitic beneficial insects however the program failed to establish a local population that could withstand our winters and the program has been shelved.

Elms can be magnificent trees however onging use of toxic chemicals is a high price to pay and therefore if you have a young tree or tree in poor condition we’d encourage you to replace it with an alternative species. As you have probably read regularly, take a walk around your area and choose a replacement tree species that does well locally.

We have heard very good reports from a duck owner as the duck would guard the base of the tree and when the Elm Beetle larvae came to ground to pupate, the duck would hoover them up. If your considering the duck experiment we urge you not to use any chemical treatments for a few years prior.

We are very keen to hear about (and promote) any other organic methods to control Elm Leaf Beetle or other insect species that does not harm the environment, let us know.

Does injecting / drilling / micro injection hurt the tree?

Absolutely. The degree of damage depends on the age, species, location and condition of the tree. Also the hole size, type and number of times it is injected.

Stem injection or micro drilling for Elm Beetle treatment is however effective, quick and cheaper for us to do and therefore more profitable.

Drill or injection holes over the longer term (think in ‘Tree Time’ not human time) can introduce decay to the trunk and prematurely destroy the tree. This damage will not be evident for many years and we’ll probably be long retired when the repercussions become evident. Not all trees injected will decay and fall over but many may see significant problems.

Some more light reading.

ELB minor damage
After treatment of Elms there will usually be some minor leaf damage. The Beetles will emerge in spring and eat holes in leaves so there should be some holes evident, after this they will die and fall off. 2 to 5 holes in most leaves is not unusual and is considered acceptable damage.

Is soil injection for Elm Beetle control bad for the environment?

Absolutely. The chemicals, though widely used, kill things and damage the environment – that’s bad.

Soil treatment and Stem / trunk injection use the same active ingredient, with soil injection it is introduced to the tree via the soil rather than the trunk. For soil treatment more chemical is required and those organisms within the soil that are susceptible, good or bad, can be harmed or killed. Chemicals in the soil are taken up into all plants in the immediate area, whilst Elms are wind polinated many of the other plants nearby will be insect polinated and those polinators will be harmed

Both methods, trunk or soil, introduce a neonicotinoid insecticide into the environment, however stem injection reduces the broader impact of the chemical on the environment and therefore we usually recommend stem injection over soil treatments.

Or ducks.

Can I fix my tree after it has been eaten by Elm Leaf Beetles?

Once Elm Beetles eat holes in a leaf the leaf is damaged for the season, however regardless of how badly an Elm tree is eaten in one year, so long as tree health is good, the next years growth should be fine.

Treatments done prior to the new growth can stop any major damage for that year as well as following years.

How much does it cost for Elm Leaf Beetle treatment?

The cost depends on the size of the tree and the treatment used, the normal treatment is stem injection and the cost is calculated on the trunk diameter above the root buttressing. If you have more than one tree the 2nd, 3rd, 4th tree is cheaper due to economy of scale. The first tree can range in price, for a 3 year treatment, from $160 to $360. We offer a 2 year guarantee on our Elm Leaf Beetle treatments.

If you have neighbours with Elms there are reasonable savings to be made if we can treat a number of trees at one visit. The efficiencies and reduced driving time means all the tree owners receive a worthwhile discount.

Will Elm Beetles and the leaf damage, kill my Elm Tree?

Trees need leaves (or needles or phylodes) so if Elm Beetles continually defoliate an Elm tree then the tree could die, however one or two years Elm Beetle defoliation is not going to kill the tree unless there are some other health issues in place and the Beetle attack tips the tree over the edge.

Does the Elm Beetle chemical treatment affect or kill other plants?

The chemicals used for Elm Leaf Beetle management are insecticides not herbicides so they don’t harm other plants.

The chemical in the soil can harm organisms – insects, the drilling of a trunk for stem injections will permanently harm the tree, the spraying of foliage will harm every insect it contacts……there is some good news however, if you have an Azalea or Rhododendron nearby with silvering leaf then the chemical should clean up the Azalea Lace Bug at no extra charge!

Do Elm Leaf Beetle chemicals kill animals, bees or other insects?

The chemicals used for Elm Leaf Beetle control are insecticides so nearly any insect contacted will be impacted. This includes insects in the immediate area of a soil injection treatment. The primary active ingredient is Imidacloprid.

Our native bees don’t tend to forage on Elm trees due to location, flowering and species so this does not appear to be a serious concern. Larger animals are not generally affected, the chemical is widely used in agriculture and for applications such as domestic animal flea collars, we have heard of no associated problems in Australia. Overseas the chemical has been heavily criticized for its environmental impact particularly on bees because of its extensive use in many areas of agriculture.

Chemical use for Elm Leaf Beetle control in Australia accounts for a very small part of the use of this chemical.

Though the negative outcomes related to Elm Leaf Beetle treatment appear fairly minor (in comparison to widespread agricultural use) we encourage clients to use treatments for the Elm Beetle and larvae sparingly, possibly be prepared to see some damage in some years and use organic measures where possible to reduce the number of treatments required and the cumulative impact on the environment.


ELB Snail on Elm leaf
Though not common it is possible some holes in Elm tree leaves may be from snails, the holes are larger and less regular than from Elm Leaf Beetle.

Variations on the same questions.

What are these tree beetles in my Golden Elm?

Most European Elm species are susceptible to Elm Leaf Beetle damage including English elm Ulmus procera, Dutch elm U. x hollandica, Golden elm U. glabra”Lutescens”, Variegated elm U. minor “Variegata”, and the Weeping elm U. glabra”Camperdowni”. Asian species however such as the Chinese elm U. parvifolia and Japanese Zelkova Zelkova serrata are relatively resistant to elm leaf beetle attack.

What is causing the Elm leaf damage on my tree?

Elm leaf damage is usually from Elm Leaf Beetles – see above. There are a range of tree / leaf treatments available, see below.

What is wrong with my Elm tree leaves?

If there are holes or skeletonization of the Elm leaves this will be the beetle however curling of the edges, chlorosis and dieback are usually related to other problems such as water or heat stress except late in the season when beetle damage to Elms can start to look (from a distance) like water stress. You may also see som snail damage.

How do I stop these Elm tree bugs?

Presently there is no absolute solution for Elm Leaf Beetle, most trees are treated with chemicals, we suggest each three years, this controls the beetles.

How do I remove Elm Leaf Beetle from my tree?

As detailed above on this page there are management practices for Elm Leaf Beetle but no way of permanently removing them. This said, with regular treatment the Elm Beetle damage is usually minor and sometimes unnoticeable. Hopefully your neighbours tree is also getting treated as there can be some crossover.

Melbourne Arborist