Is heat treatment a viable option for destroying weed seeds in biosecurity risk goods?
The prevention of biosecurity threats is an international priority and the development of improved phytosanitary treatment technologies is part of New Zealand’s biosecurity science strategy. Twelve temperature/time treatments were investigated as potential methods to devitalise weed seeds. Six weed species, Digitaria violascens, Eleusine indica, Lepidium virginicum, Plantago lanceolata, Portulaca oleracea and Sonchus oleraceus were exposed to treatments of 50°C, 60°C or 70°C each for 1.5 h, 4 h, or 15 h. The efficacy of these treatments was compared with those of two industry standards: (i) 85°C for 15 h at 40% RH; and (ii) methyl bromide (80 g/m3) for 24 h. The standard treatments were significantly more effective at devitalising weed seeds than the experimental treatments. This study showed that temperatures below 85°C are generally insufficient for devitalising seeds of the weed species examined.