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16 November 1998 |
Ref 98/267 |
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CSIRO has launched a pre-emptive strike against potentially one of the most damaging woody weeds of the grazing industry in northern Australia.
The target is mesquite, a relative of the devastating Mimosa pigra, which is threatening large areas of Kakadu National Park . A leaf-tying moth and a sap-sucking bug have now been released in Queensland, Northern Territory, Western Australia and New South Wales.
Mesquite (Prosopis sp.) is a serious woody weed found throughout mainland Australia which was introduced early this century as a shade and fodder plant. It has potential to increase beyond its current distribution and become a serious pastoral and environmental weed.
"We have four species of mesquite and some hybrids naturalised in Australia, all of which have come from the Americas," says Dr Rieks van Klinken, the scientist in charge of the project.
"Overseas these weeds have been responsible for transforming vast tracts of open rangelands into thorny shrub forests. In the US, mesquite causes an estimated loss of $1 billion annually to the livestock and support industries. Currently these negative impacts are occurring at a local scale in Australia but the costs would be enormous if mesquite was to reach its potential distribution."
Current control programs rely on chemical and mechanical methods with limited use of fire and stock management. The hardiness of mesquite, together with high seed production and a long-lived seed bank, means that control costs are high and long term. In addition infestations typically occur in remote, commercially low-value regions.
CSIRO Entomology began a biological control program for mesquite in 1994. A leaf-tying defoliating moth (Evippe sp.) has now been released in Qld, NSW, WA and the NT. The sap-sucking bug (Prosopidopsylla flava) was released in November 1998 in WA. It is planned that a further 24 releases of both the moth and the bug will be made by March 1999.
Both species attack the leaves. The moth larvae tie leaves together with silk then feed and pupate and in Argentina this species has defoliated "many miles"of mesquite. The sap-sucking bug punctures the leaves, injects toxins and sucks out the sap. Heavy infestations cause die-back and can kill entire plants.
"Both species should slow the expansion and thickening of infestations and increase the time the weed takes to reach reproductive age (currently about 3-5 years)," Dr van Klinken says.
"By hitting regrowth and surviving plants, mechanical and chemical treatments may be more effective in eradication programs, with the possibility that fewer treatments will be required to exhaust the seed bank."
More information:
Dr Rieks van Klinken Ph: (07) 3214 2749
Email: rieks.vk@brs.ento.csiro.au
(Australia's largest scientific research organisation)
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