At one time recognized as the worst weed in NSW Bathurst burr is one of the worst causes of vegetable fault in wool and seedlings are poisonous to animals, particularly horses and pigs. Competes with Summer crops and reduces pasture productivity. The seeds of Bathurst burr are well adapted to spread by means of the hooked spines on the burrs. The burrs also contaminate seeds of Summer crops and will float on water and move along watercourses. Control is by herbicides or mechanical means such as hand hoeing, mowing or slashing which must be done before burrs are formed. Some control by biological means has been achieved (fungus, insects and rust).
The photograph is of Bathurst burr (Xanthium spinosum L.)
(See the information on Noogoora Burr relating to the taxonomy of the Xanthium genus. Parsons & Cuthbertson give the scientific name of Bathurst burr as Xanthium spinosum L.)