You may be surprised to learn that the Elm Leaf Beetle has only existed in Tasmania for approximately 20 years, with the first case detected in Launceston in 2002 and in Hobart in 2008.
Despite their recency, Elm Leaf Beetle has become well established in both the north and south of the state. This is no fun novelty: Severe cases of Elm Leaf Beetle can defoliate an Elm tree in just over a week if left untreated.
Because of the degree of damage they can cause, the ability to identify Elm Leaf Beetle is an important skill in your tree-care-arsenal.
In this article we will answer:
- How do I identify Elm Leaf Beetle?
- What is the life cycle of the Elm Leaf Beetle?
- What symptoms will my Elm tree exhibit if it is infected?
- How is Elm Leaf Beetle managed?
- How can we help?
How do I identify Elm Leaf Beetle?
Typically, you’re more likely to notice that your tree is in distress before spotting individual beetles in your Elm tree. Having said this, there are many beetles that can damage Elm leaves. So, it’s important to be able to identify and distinguish the Elm Leaf Beetle to gauge if your tree is at real risk.
Adult beetles grow to be around 6mm in length and sport gold/yellow/olive green and black stripes. See Figure 1.
Their eggs in contrast are lemon-yellow in colour, and can be found in clumps on the underside of Elm leaves. Once hatched, the larvae appear small and black, and grow to be 12mm long in the summer months. By this point, the larvae will appear like caterpillars with yellow markings.
An adult Elm Leaf Beetle
Elm Leaf Beetle larvae making “shot-holes” in the leaf
What is the life cycle of the Elm Leaf Beetle?
Adult female beetles tend to lay their eggs on the underside of leaves in spring, after which the larvae will hatch after roughly 7 days. At this stage in their life cycle, the larvae will spend the summer feeding on the softer parts of the Elm leaves until they migrate down the tree to find shelter. While hiding in crevices in the bark at the base of the tree or in the soil, they will pupate (begin their process of become an adult beetle).
When the cooler months roll around, Elm Leaf Beetles will seek shelter in wood piles, sheds, or similar spaces.
What symptoms will my elm tree exhibit if it is infected?
The most noticeable symptom of Elm Leaf Beetle is visible in the leaves. Larva and adult beetles feed on the Elm leaves, leaving them skeletonised or “shot-holed”, see Figure 2. Severe defoliation can occur in large infestations, and consecutive years of defoliation can cause stress to your tree, reducing its health and condition. The stress can leave your tree vulnerable to other pests and diseases, and less able to cope with environmental stressors such as low rainfall or high temperatures.
In addition to making your tree look sick and unattractive, Elm Leaf Beetles can often be found entering your house through windows and doors.
How is Elm Leaf Beetle managed?
Luckily, there are a number of ways we can help you battle Elm Leaf Beetle. It must be noted, the most effected methods of treatment should only be conducted by qualified arborists or pest control operators. Your arborist must have the appropriate training and certification to handle these chemicals.
Generally, maintaining the health of your tree is the most important thing you can do to reduce the effect of the beetles. This can include spreading mulch around the base of the tree, from just outside of the trunk to the edge of the crown. A layer of mulch and regular watering can go a long way in reducing the impact of damaged foliage.
Figure 3. Tasmanian Tree Care conducting stem injections at the base of an infected Elm tree
Figure 4. A small diameter drill bit can reduce the risks caused by invasive drilling
A more DIY approach may include adhesive tape, which can be applied directly to the trunk of the tree. Timing is key with this control method, as the tape will trap larvae as they migrate down the tree. Then, the tape must be inspected for larvae and replaced every week in the spring.
Elm leaf beetle control methods such as soil drenches and sprays have been a traditionally accepted method of treatment. This is where insecticide is applied to the tree’s rhizosphere (root zone) or canopy. This is an effective method of controlling the pest but can have a damaging effect on non-target species such as bees, ladybugs or other ecologically important species. Because of this, stem injection is considered to be the most environmentally responsible method.
How can we help?
Tasmanian Tree Care provides professional solutions to Elm Leaf Beetle for any commercial or residential property. If you’re unsure about the health of your natural assets, please contact us to organise an assessment. It’s true what they say: prevention is the better than a cure.
Figure 1 & 2 curtesy of Getty Images/iStockphoto and Didier Descouens, sourced from Wikipedia under Creative Commons license.
Content collected by Jack Colbeck
Jack Colbeck is an understated high achiever with skills, humility and humour in equal measure. Jack is responsible for quality control and delivering professional tree services to our valued clients. Jack is passionate about growing and planting trees to offset the negative impact of removing trees.
Elm Leaf Beetle FACT SHEET
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