The mortality of Siam weed (Chromolaena odorata) caused by fire in the Wet Tropics of northern Australia

Paul WilliamsA, Justine DouglasB, Mark ParsonsC and Merl RobertsB

A Queensland Parks and Wildlife Service, PO Box 5597, Townsville, Queensland 4810, Australia.

B Queensland Parks and Wildlife Service, PO Box 74, Cardwell, Queensland 4849, Australia.

C Queensland Parks and Wildlife Service, PO Box 1293, Ingham, Queensland 4850, Australia.


Siam weed (Chromolaena odorata (L.) R.M.King & H.Rob.) is a significant threat to nature conservation and agriculture in northern Australia, due to its dense smothering habit. The effect of a mid dry season (September) fire on the mortality of Siam weed was assessed at Jalum Conservation Park, near Tully in the Wet Tropics of north-eastern Queensland. Fire caused an overall mortality of 52%. This included an average mortality per plot of 76% of plants that were less than 1 m tall and of 28% of plants that were greater than 1 m tall prior to the fire. The surviving Siam weed resprouted from sub-soil buds located at the base of stems. The reduced size of plants following fire facilitated access for herbicide application. This study indicates that fire may be of value as part of an integrated control program by killing some plants, especially those <1 m tall, and by improving access for herbicide application.


Plant Protection Quarterly (2004) 19 (4) 135-136.