Some like it hot, but moth plant does not : the effect of commercial composting on moth plant (Araujia hortorum) seed viability

Abstract

Invasive plants threaten native biodiversity and ecosystem structure and function. Although the removal of invasive plant material is important for the conservation of native plant communities, the disposal of live seeds and propagative material can assist the spread of the invader. Commercial-scale composting windrows can reach temperatures sufficient to render weed seeds unviable, but research has shown that results vary intraspecifically. Here we examine the effects of commercial composting on the viability of the invasive vine moth plant (Araujia hortorum). Moth plant seeds were subject to preliminary viability tests to evaluate background viability and to allow post-composting comparison. Mature pods were then buried in a commercial composting windrow for 33 to 99 days, and assessed for viability by tetrazolium assay and germination trials. We further examined the minimum temperature and exposure time required to kill seeds using incubation and water-bath experiments. Background seed viability was estimated at 99%. After composting in a windrow with a mean temperature of 59°C, seeds were no longer viable. Exposure to temperatures of at least 55°C was lethal to hydrated moth plant seeds in laboratory experiments; however, dry-incubated seeds were substantially more resilient. Overall the findings of this study suggest that large-scale composting windrows maintained above 55°C are an effective and reliable method for the disposal of moth plant pods.