Broom gall mites, released and monitored by the Otago Regional Council, have proven an effective weapon for combatting broom and restricting its invasion.

The mites have been found in the Strath Taieri area up to 30 kilometres from release points, indicating a good spread and a strong infestation among broom plants.

Team Leader Biosecurity Compliance, Richard Lord, says the mites were having a “real impact” in some areas.

“What’s exciting is we’re finding the mites popping up in so many locations now. For instance, we found infestations of the mites right up the Taieri River, from Sutton to Hyde. They’re finding their way into new areas of their own accord, travelling for kilometres on the wind.”

The mites prove that sometimes the best results require a patient and consistent strategy, he says.

“There’s still a long way to go – and there are no silver bullets in pest management – but we’re quietly hopeful about the long-term effectiveness of the broom gall mites.”

Introduced into Otago in 2012, the broom gall mite is a microscopic organism which colonises and feeds on broom, gradually forming white galls on the plants which can stunt their growth and eventually kill them. As its name suggests, the mite only attacks broom, making it an effective weapon against the invasive bush while protecting our native plants.

ORC’s Proposed Regional Pest Management Plan lists the aggressive and hardy plant, brought over by settlers in the 1800s, as a pest to be managed under sustained control programmes.

In addition to ORC’s biocontrol measures, landowners have a responsibility to limit the spread of gorse and broom. As 53% of Otago is designated gorse and broom free – including large areas of Central Otago and the Queenstown Lakes – occurrences of the plants are low and should be dealt with individually by landowners.

Landowner options for gorse and broom management include spraying, digging the plants out, cutting them down and treating the stumps, or applying granular herbicides.