Why Elm Leaf Beetle is a problem for my tree
The damage to leaves by the feeding activity of adult beetles and larvae weakens Elm trees. Severe damage by the beetle causes leaves to die prematurely, while weakened trees are more susceptible to other stresses such as drought, or attack by other pests and diseases. Repeated over several seasons, such damage can result in dieback of otherwise healthy trees or the decline of already stressed or weakened trees. However, treatment is available that can protect your Elm trees for up to three years, helping your trees to thrive.
Life Cycle and Identification
Adult beetles hibernate during winter in sheltered places such as bark crevices, sheds and woodpiles. Around mid October beetles emerge from hibernation, and with rising spring temperatures, begin feeding on elm leaves. Adult beetles chew small round holes through leaves, creating distinctive ‘shot hole’ damage.
In early November the beetles lay clusters of lemon-yellow eggs on the underside of leaves. Within 7-10 days larvae hatch. Larvae are voracious feeders, removing leaf tissue from between the leaf veins – this damage is referred to as skeletonising. Heavy skeletonisation causes the leaves to turn brown and drop prematurely.
Maturing within 2-4 weeks, larvae either crawl down the trunk or drop from the canopy, pupating at the tree base or in bark crevices. Adult beetles emerge about 10 days after pupation, repeating the cycle. In Melbourne there are typically two and sometimes three generations of beetle per year.
Controlling Elm Leaf Beetle
There are several ways to control Elm Leaf Beetle, each varying in effectiveness. Ideally, protection from all stages of the beetle’s life cycle will avoid any damage to trees and help your trees to thrive. Effective protection can be achieved for 2-3 years using either soil or stem injection and can be carried out by Arbor Co’s certified and experienced technicians.
Arbor Co maintains mandatory treatment records and advise our clients when repeat treatments may be necessary.
Soil injections require using a specialised injector to deliver the treatment into the soil under the tree canopy. The chemical is taken up by the tree’s roots and transported to the leaves where it is ingested by feeding beetles and larvae. A minimum of two weeks from application is required for the treatment to take effect.
The ideal timing for soil injections is from late winter until early spring, and moist soils are required for the treatment to be effective.
Stem injections use a specialised injector to deliver the treatment directly into the tree trunk, where it is transported to the leaves where it is ingested by feeding beetles and larvae. A minimum of five days from application is required for the treatment to take effect.
Although stem injections can be applied at any time of the year, the ideal timing is from late winter until late spring. Stem injection is particularly useful where site constraints prevent effective soil injection or where fast-acting treatment is required.
Elm Leaf Beetle FAQs
When is the best time to treat for Elm Leaf Beetle?
The tree can be treated all year round, but the ideal time is between July and the mid November.
What is the treatment guarantee?
We guarantee the treatment for one year and suggest treatment every three years.
What is the cost of treatment?
For residential customers $150-$300 depending on the size of the tree. Discounts apply for multiple trees
What is the difference between Stem injection and Soil injection?
Stem injection delivers the chemical directly to the tree trunk.
Soil injection delivers the chemical to the trees roots via the soil using water to deliver the chemical.
While Arbor Co undertakes both stem and soil injection, and both are effective at treating Elm Leaf Beetle, Arbor Co prefers stem injection as this method:
- is quicker to get the chemical to the leaves (5-10 day for trunk inject and 14-21 for soil inject),
- doesn’t rely on favorable site conditions such as adequate soil moisture levels to be effective,
- contains the chemical in the tree, with no chemical exposure to the surrounding environment (soil inject can leave chemical in soil and other surrounding plants),
- targets Elm Leaf Beetle. (any roots in contact with soil injected chemical will uptake the chemical – if bee-pollinated flowering plants absorb the chemical it can harm bees that feed on the flower).
What if I see damage on my treated trees?
Even treated trees will experience some initial damage early in the season. Adult beetles emerging from hibernation need to feed on the treated leaves to be killed. Should you observe skeletonisation (larvae damage that appears like lace) you should call our office on 1800 801 565 .
Are treatments harmful to the environment?
The chemical used has low toxicity to humans and other mammals, although it is harmful to fish, birds and some soil organisms. Arbor Co prefers treating trees via stem injection containing the chemical wholly within the tree, thereby minimising exposure to the environment.
Further information and useful products
Not sure which treatment’s right for your tree, or simply want more information? Please contact our office to speak with one of our friendly Plant Health Care staff on 1800 801 565.
For the commercial operator, Treelogic Tools has a wide range of stem injection equipment, and access to some of the best arboricultural text books available in our online shop.