Moth Joins Battle To Cut Mimosa Down To Size

CSIRO has Government permission to release Leuciris fimbriaria from quarantine. The larvae of this moth are caterpillars that feed on the leaves of mimosa. Extensive tests showed that these caterpillars cannot feed or grow on any plant other than mimosa.

Mimosa, or the giant sensitive plant, forms impenetrable thickets across more than 800 km2 of the Northern Territory, threatening Kakadu National Park and other wetlands in tropical Australia and Asia. It has also made an appearance in Queensland.

CSIRO entomologist Dr Tim Heard says the first releases will be made near the Alligator River in the Northern Territory and the larvae of the moth will then be free to munch their way through as many mimosa leaves as they can.

"If populations of this insect build up, their feeding will reduce plant growth and seed production, making mimosa easier to manage or even knocking it back to the extent that it is no longer a problem," Dr Heard says.

"Where mimosa blankets the landscape, it reduces biodiversity, competes with pastures and hinders access to water. It is also a serious conservation problem because of its ability to completely alter the landscape of the floodplain." He adds that mimosa is one of 20 Weeds of National Significance.

Mimosa spreads at an alarming rate. After good rain, infestations can double in just over a year. In its home range, which stretches from Mexico to northern Argentina, it occurs in small patches of inconspicuous and straggly plants, but in Australia it grows to six metres and forms impenetrable thorny thickets.

The new moth will join a suite of agents from its native range that have been released over the last 21 years to control the plant and which are now having a noticeable impact. The agents - seed feeding beetles, stem boring moths, flower feeding weevils and root feeding beetles - have been specially chosen to attack different parts of the weed.

Mimosa was introduced to Australia from tropical America in the late 1800s as a curiosity. People were fascinated by the fact that when the leaves were touched, they folded up. But the plant escaped from the Royal Darwin Botanic Gardens and entered the Adelaide River system.

Ongoing releases and evaluation will be done in collaboration with the Weed Management Branch of the Northern territory's Department of Infrastructure Planning and Environment. The research was funded by the Australian Government's Natural Heritage Trust through their Weeds of National Significance program.