Eradication of Red witchweed – one step at a time!

Abstract

The parasitic weed, Red witchweed (Striga asiatica) (L.) Kuntze) was first recorded at Habana, near Mackay in July 2013, the only known infestation to have established in Australia. An eradication response program was endorsed and commenced 1 July 2015 involving a treatment period of 3 years. A ‘targeted adaptive three zone approach’ was adopted, utilising the integration of three treatment methods (planting of false host crops, herbicides and ethylene fumigation) to specific sections, or zones, within each infested property, with the aim to expedite RWW soil seedbank depletion and minimise emergence.

This paper will outline the treatment progress made to date and challenges encountered. The planting of the false host, soybean, in the high priority zone was completed in 2015-16, 2016-17 & 2017-18. High rainfall occurring in the RWW area during 2016 (1607 mm) and 2017 (2100 mm), necessitated an active weed control program within the soybean crop. Potential grass hosts amongst the soybean; needed to be destroyed before RWW could germinate, establish and set seed.

To accelerate RWW soil seed bank run-down ethylene gas was also injected into the soil at 1.5 to 2.0 kg/ha using a custom-made delivery system during the autumn period. Once delivered ethylene gas disperses readily through the soil from the point of injection, saturating the soil profile, initiating germination of any red witchweed seed in the soil that are in a pre-conditioned state. An integrated research field trial (efficacy trial) has also been established on an infested property examining 16 control options to help govern the management strategies utilised within the RWW eradication program.