THE potentially serious weed three-horned bedstraw has been confirmed on two unrelated properties in the Central and Great Southern agricultural regions.
Targeted surveillance by the Agriculture Department revealed bedstraw plants scattered over 100ha in the Central Agricultural region property in late August.
The property was next to a 2004 barley paddock where bedstraw was found in a harvest sample.
The barley paddock was quarantined in 2004.
The plants found recently affirmed that the bedstraw seed present in last year's barley sample did originate from that paddock.
Infested paddocks and high-risk areas will be placed in quarantine and subjected to an eradication program.
Agriculture Department weed scientist Jon Dodd said grain samples collected by Cooperative Bulk Handling during the 2004 harvest from the affected farm and from other farms in the district indicated that the infestation was limited to just the one property.
Dr Dodd said Agriculture Department staff had recently carried out on-ground surveillance at the known farm and other linked properties now that bedstraw plants were visible in crops and fallow.
To date this is the only property in the Central Agricultural region known to have this weed.
Bedstraw plants found during the surveillance have ranged from seedlings to flowering plants.
All have a characteristic sticky feel due to their covering of minute hooked bristles.
Fully grown plants have a straggly, scrambling or climbing habit, with weak, branched square stems that can be up to 1m long.
In the Great Southern region, a new infestation of bedstraw was found in an oat crop.
Dr Dodd said thorough searching confirmed the weed's presence in about 0.5ha of the crop.
The affected area has since been sprayed with glyphosate.
Grain from the crop is likely to be exported to minimise the risk of spreading bedstraw seeds to other areas in WA.
"The presence of the weed in crop-free areas within the oat crop indicates that it was not introduced with the seed, but more likely with feed grain that was fed out in the paddock in previous seasons," Dr Dodd said.
"In this instance, we are conducting trace-back activities to identify the source of the bedstraw seed that infested the crop.
"The bedstraw-affected paddock will be placed in quarantine."
This latest find in the Great Southern appears to be unrelated to the three previous discoveries of this weed in WA.
Three-horned bedstraw is a declared weed in WA.
Its classification prohibits the movement of contaminated machinery. Contaminated produce, including livestock and fodder, may not be imported and all plants found must be destroyed.
Dr Dodd said bedstraw was a competitive climbing plant similar to cleavers that formed dense masses of tangled vegetation in crops, along fence lines and in wasteland.
"Bedstraw is a major weed of crops in south-eastern Australia and could become a serious problem in WA if allowed to spread in crops," Dr Dodd said.
"It can be controlled by herbicides in cereals, but is more difficult to control in canola and legume crops.
"An economic analysis of this weed conducted by the Department of Agriculture in 2003 showed a cost to farmers of weed control and foregone yield of as much as $596 million over 12 years if this weed became widespread and fully established in this state."
Colour photos to aid identification are included in Farmnote 97/96 Bedstraw and Farmnote 87/96 Cleavers available from Agriculture Department district offices and at www.agric.wa.gov.au
Bedstraw plants will be on display at the Merredin Research Station field day on September 22.
Suspect samples of bedstraw can be taken to the nearest office of the Agriculture Department for identification or posted to AGWEST Plant Laboratories, Locked Bag 4, Bentley Delivery Centre, WA 6983.