Horehound in a perennial weed found widespread in southern Australia. It invades disturbed bushland, farmlands and rocky outcrops, decreasing pasture productivity as animals avoid grazing due to its bitter alkaloid taste. The spiny burrs of horehound also decrease the value of wool contribute to the spread of the weed as burrs attach to the fleece of animals and disperse as they graze. The following biocontrol agents have been released to combat the spread of horehound.
1. Horehound clear-wing moth *Chamaesphecia mysiniformis*
2. Horehound plume moth *Pterophorus spilodactylus*
The combined effects of these two biocontrol agents is expected to reduce the spread and growth vigour of horehound in Australia. Since its first release in 1995, the horehound plume moth has established in 90% of its original release sites in SA, ACT, NSW an TAS. At high infestation densities, the larvae of the plume moth have been recorded to reduce plant biomass and life-span. Likewise, the horehound clear-wing moth was fist released in 1997 in Wyperfeld National Park, Vic. Establishment was confirmed in 2001 and since then many more release projects have been undertaken. Regular updates on field days, workshops, and research results are published on the Blog.
Horehound weed, photo: Matt Lavine [CC BY-SA 2.0](https://creativecommons.org/licenses/by-sa/2.0/deed.en)