ELM LEAF BEETLE

The Elm Leaf Beetle (ELB) (Pyrrhalta luteola) was discovered in Victoria some time in 1989. It is thought it could have arrived, possibly from the USA, in someone's suitcase. As nothing was done for some time, the insect became well established and populations built up before any measures to restrict the spread were introduced. In the early 1990's entomologists from the USA were asked to assist, and staff at the Keith Turnbull Research Institute (KTRI) at Frankston have worked steadily on the problem. Two biological control insects have been imported and tested prior to release. However, to date neither has survived from one season to another in sufficient numbers and an effective biological control has yet to be established, although work is continuing.

In the meantime ELB has spread and is now established in eastern areas of Victoria including the Mornington Peninsula, Gippsland, Berwick, Dandenong Ranges, and the southern and eastern suburbs of Melbourne, and is beginning to spread to western Victoria. As the beetle is a hitchhiker, it is expected to continue its spread throughout South-Eastern Australia, unless it is checked by some means.

Life cycle
The beetle hibernates in winter in sheltered places. When temperatures in spring reach a certain level, the beetles emerge and feed on young elm leaves (can be any elm species). Their presence is made known by shot-holes in elm leaves. The beetle is described as the size of a small pea, and is either yellow with black stripes or could be bronze in colour. As the season advances, the beetle lays tiny eggs on the underside of elm leaves. These are described as a double row of 'miniature lemons'. They hatch in 7 to 10 days. At first the larvae are small and black. They feed on the leaves by eating the green matter, leaving a skeleton of veins, and reach a size of 12mm when they are described as 'slug-like'.

At this stage they migrate down the trunk of the tree, and they pupate either in the ground or in crevices in the bark of the lower trunk. After a relatively short time new beetles emerge from the pupae and in warm climates a new generation carries on breeding. In southern Victoria, 1-2 cycles occur per year depending on the length of the summer. The new generation of beetles continue to feed on the leaves of elms for several weeks but with the onset of cooler weather, seek shelter for winter in various places, including motor cars, where they hibernate until October.

A HEALTHY ELM IS MORE LIKELY TO SURVIVE

A healthy elm is less likely to be devastated by ELB:

SIMPLE WAYS TO REDUCE POPULATIONS
Trunk banding is the simplest way of breaking the life cycle of the ELB. By observing the growth of the larvae and banding the trunk(s) of the elm tree prior to the descent down the trunk (usually about Christmas time) significant numbers of larvae can be killed. The Friends of the Elms recommend *TAC GEL (*TAC GEL IS DISTRIBUTED BY FERTOOL, Ph: (03) 9796 4433), or TRAPP IT. These are non-poisonous sticky materials which can be plastered around the trunk (two narrow bands separated by about a hand-span) to trap the larvae. They are available from leading retail nurseries in various sized containers. Although not cheap, one application is all that is required and the material keeps well and can be used for a number of seasons.

For those who are looking for a cheaper form of tree banding, wrapping the trunk with sticky tape, with sticky side outwards to trap the larvae, can be effective provided it is in place at the right time, which is between the second half of December and the first half of January. The tape needs to be removed and replaced when it is covered with beetles. In the event of heavy rain, it would be necessary to renew the banding.

Trunk banding can also be achieved by spraying or painting a Carbaryl solution on the trunk in a half-metre wide band. Carbaryl is a poison and therefore all manufacturers' recommendations should be followed and the band should be high enough up the tree to avoid contact with children or pets. Make sure you use a Registered product containing Carbaryl where the Directions for use to control Elm Leaf Beetle on elms is on the label. Examples of Registered Products with such claims are as follows:

NOTE:
Before using any pesticide, always read the label and make sure it is registered for use against Elm Leaf Beetle. Products not registered for ELM will not provide the correct information. Please read the disclaimer.
Disclaimer: Whilst all care has been taken in preparation of this information, it is intended as a source of information only. Friends of the Elms does not accept responsibility for the contents. It urges that only pesticides with labels which refer to their use in connection with Elm Leaf Beetle be used. Such pesticides must be used as directed on the label.

More Effective But Difficult Solutions
Spraying of elm leaves when larvae or beetles are feeding on the leaves is more effective, but for advanced trees it would be necessary to call in a contractor with special equipment. Btt "Novador", a non-poisonous spray, is used by local government and should be available to contractors.
A relatively new development is soil injection of a systemic insecticide. This is proving to be one of the most effective methods of reducing ELB attack. The soil beneath the elms is injected with Imidocloprid, which the tree absorbs into the leaves, and this is fatal to leaf eating insects.
It is effective to use this treatment in spring when the sap is flowing. It is believed that it will only be necessary to treat each tree every 2 or 3 years. It needs to be administered by contractors using special equipment.

Help from Councils
Many local councils offer valuable information and help with ELB infested elms. If your council does not yet provide these services for the elm trees in their municipality, PLEASE KEEP ASKING THEM UNTIL THEY DO. It is important that everybody joins the fight against ELB.

WILL ELB KILL THE ELMS?
Although heavy infestations of ELB can completely defoliate an elm, this does not occur until late in the season. The elm will send out new leaves in the next season. However, the growth of the tree will be affected and ultimately ELB may lead to its demise. By taking steps to reduce the ELB populations, the damage can be much reduced. Experiments at the Keith Turnbull Research Institute showed that banding can be effective in reducing the damage to leaves by more than 50% in the case of English Elms, over a three year banding program, applied at the right time in the ELB cycle.

More info on ELB.

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