Elm Leaf Beetle

The Elm Leaf Beetle (Xanthogaleruca luteola) was first discovered in Victoria in 1989 and has since been detected in South Australia from 2009. There are now wide spread infestations throughout our Elm Trees in South Australia.

The majority of Elms planted in our streets, parks and gardens are European species and are susceptible to attack. The Asian species such as the Chinese Elm are relatively resistant to attack.

An infestation of Elm Leaf Beetle will result in severe defoliation. The infested trees will produce new foliage; however it is likely to be smaller and sometimes distorted. Elms that suffer from repeat attack will become weak and this greatly reduces their aesthetic and amenity value. Trees will also be more likely to succumb to other pests and diseases.

Life Cycle
In order to control the insect, it is important to have an understanding of the beetle’s life cycle.

September –The adult beetles begin emerging from shelter. If there is insufficient foliage on the trees, they will die.

October-Most adult beetles will emerge and fly to Elm trees to feed on new foliage. The beetle is not easily seen but their presence will be evidenced by shot hole damage on the leaves.

November-The beetles will mate and lay egg clusters on the Elm leaves. The eggs look like a small double row of lemons. The eggs will take 7-10 days to hatch.

December-The larvae begin to hatch. They feed on and skeletonise the foliage on the Elms. They will grow from one to ten millimetres in length and then move down the branches and trunk to pupate.

The Elm Leaf beetle pupae are usually five millimetres in length and are a bright yellow in colour. They will be found on the ground surrounding the base of the tree and within the textured bark. In about 10 days, the adults emerge to start the cycle again.

January to March – The second cycle will have been completed. By the middle of March, the beetles disappear and find shelter to hibernate for the winter.

Control
– Hand Picking – OK on a small developing tree, however laborious and not practical on larger trees
– Spraying: Horticultural Oil – need to cover entire leaf including underside for any ‘smothering’ effect
– Spraying: Insecticide – caution with drift of a chemical over yard and neighbours. Full spray protection required.
– Banding – stick band at base of tree will capture adults moving down and pupae moving up
– Injection – injection of systemic chemical into trees cambium. Best done during active growing – Spring & Summer.