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Abstract
Woody weeds pose significant threats to the 12.3 billion dollar Australian grazing industry.
These weeds reduce stocking rate, increase mustering effort, and impede cattle access to
waterways. Two major concerns of woody-weed management are the high cost of weed
management with respect to grazing gross margins, and episodic seedling recruitments due to
climatic conditions. This case study uses a Stochastic Dynamic Programming (SDP) model to
determine the optimal weed management decisions for chinee apple (Ziziphus mauritiana) in
northern Australian rangelands to maximise grazing profits. Weed management techniques
investigated include: no-control, burning, poisoning, and mechanical removal (blade
ploughing). The model provides clear weed management thresholds and decision rules, with
respect to weed-free gross margins and weed management costs.