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Beetle Threat to Horticultural Eucalyptus Crops in Ireland

Researchers at Teagasc and University College Dublin are investigating the biological control of a new insect pest of Irish forestry and horticulture. The accidental introduction of the Eucalyptus leaf beetle pest, Paropsisterna selmani into Ireland, poses a significant threat to our commercial foliage, biomass and forestry industries. This is the first paropsine leaf beetle to become established in Europe and it was initially discovered damaging foliage crops in Kerry in 2007. It is now commonly found in many areas of Cork. Even in the last few months, new information indicates that this invasive pest has spread to Wexford and Wicklow. Predictions of the patterns of spread, suggest that it is only a matter of time before it is established throughout the island and this poses a bio-security risk to the UK and mainland Europe. The colourful beetle defoliates Eucalyptus trees and even small amounts of damage renders Eucalyptus foliage crops unmarketable. In the absence of natural control, insecticide applications have been used by foliage growers, but the unfortunate side-effect of this is the disruption of the successful biological control of another invertebrate pest, a sap-sucking psyllid. Access difficulties deem that insecticides are not a viable option for the forestry or biomass sector.

A parasitic wasp, Enoggera nassaui has been used as a biocontrol agent of similar leaf beetles in New Zealand and was imported into a quarantine insectary in University College Dublin (sponsored by Coillte) for further study. Dorothy Hayden, a Lecturer at the Teagasc College of Amenity Horticulture, National Botanic Gardens, who is currently undertaking a PhD as a Teagasc Walsh Fellow, is investigating the suitability of this egg parasitoid as a biocontrol agent for the leaf beetle in Ireland. The research will provide the necessary information to fulfil the requirements of a risk assessment required, if a field release application is considered safe. The benefits of establishing a natural control agent for the beetle under field conditions include:

• retention of valuable market share and profitability for foliage growers

• growth of biomass and short rotation forestry

• resumption of biological control of the psyllid pest where insecticides had been used

• positive environmental benefits, and

• reduced likelihood of the beetle spreading to neighbouring countries.

“Our research is investigating whether it is safe to release the biological control agent into Ireland. We are investigating its response to Irish weather conditions, its success in attacking the pest species and the extent to which it will only attack the pest species,” says Dorothy.

         

The parasitoid wasp Enoggera nassaui in the act of parasitizing a beetle egg.

The eucalyptus leaf beetle pest Paropsistern selmani.

 

 

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