Is heat treatment a viable option for destroying weed seeds in biosecurity risk goods?

The prevention of biosecurity threats is an international priority. The Biosecurity Science Strategy Objective 1.7 is to develop improved phytosanitary treatment technologies. Low temperature dry heat treatments were investigated as a method to devitalise weed seeds. Six species, Digitaria violascens, Eleusine indica, Lepidium virginicum, Plantago lanceolata, Portulaca oleracea and Sonchus oleraceus were exposed to treatments of 50°C, 60°C and 70°C for 1.5 h, 4 h, and 15 h. The efficacy of these treatments was compared to that of two industry standards, 85°C for 15 h at 40% RH and methyl bromide (80g/m3) for 24 h. The standard treatments were significantly more effective at devitalising weed seeds. This study showed that reduced heat treatment is not reliable for weed seeds and could not be applied broadly across the biosecurity system for their devitalisation, due to variation between the individual species abilities to survive.