The Department of Agriculture and Food’s ongoing surveillance for priority weeds recently resulted in an additional find, with the discovery of a serious invasive weed not previously found in Western Australia.
Department priority weed response manager Kay Bailey said olive hymenachne (Hymenachne amplexicaulis), a declared plant formerly recorded only in Queensland and the Northern Territory, was discovered in the East Kimberley.
“The olive hymenachne infestation was identified by a department biosecurity officer during an aerial survey of the East Kimberley for a different weed,” Ms Bailey said.
“Steps were immediately taken by the department to determine the extent of the infestation and treat the plants, as olive hymenachne is a Weed of National Significance and prohibited in this state.
“Olive hymenachne is regarded as a serious weed due to its potential to rapidly spread from both seed and broken stem fragments.”
The semi-aquatic grass can invade wetlands, waterways, irrigation and drainage systems and low-lying commercial enterprises such as sugar cane farms.
It grows to about 2.5 metres tall and has bright green leaves with prominent, light-coloured veins, and a heart-shaped, stem-clasping leaf base.
Ms Bailey said surveillance for the weed following treatment resulted in no additional detections; however, current, wetter-than-average weather conditions were ideal for olive hymenachne to flourish.
A native hymenachne species (H. acutigluma), which has not been recorded in Western Australia, can be easily distinguished from the olive hymenachne because it does not have a heart-shaped, stem-clasping leaf base.
Following the discovery of the weed in the East Kimberley, local landholders and the community have been asked to look out for and report any unusual plants.