Fighting old man’s beard in Tasman has just taken a positive step forward with the reintroduction of old man’s beard sawfly at two release sites – Trass Valley and adjacent to the Motueka River.
The larvae stage of the sawfly does all the damage by chewing their way through leaves, which ultimately impacts on the vine’s vitality and vigour.
Old man’s beard (Clematis vitalba) is one of our District’s worst weeds, as it can climb into the canopies of trees, depriving them of the ability to photosynthesis by blocking out sunlight, which ultimately leads to the decline and death of the affected trees.
Biocontrol agents hold the best potential for widespread control of old man’s beard, but it has been difficult to find agents that are host-specific to this pest vine.
Research lab testing of several hosts known to damage old man’s beard confirmed that both the microscopic old man’s beard mite and the old man’s beard sawfly were suitable agents for release in Aotearoa as they are host-specific – or will not harm anything other than old man’s beard vines.
We purchased old man’s beard mites from Manaaki Whenua (Landcare Research) for release in 2021 and in 2022.
These flies were already approved for release by the Environmental Protection Authority in the late 1990s.
However, initial field releases of the flies failed to establish throughout the country, except for a small residual population found near the Waimea River in 2015.
New stocks sourced from Serbia in 2017 have proved to be a much fitter population of flies.
We will be monitoring these sites with great interest in the coming years.
Pictured below: Sawfly larvae and Biosecurity Officer Lindsay Barber at a sawfly release site.
