11 April 2014
Two hundred tradescantia stem beetles (Lema basicostata) have been released into a covenant just north of Kaikoura to tackle the invasive tradescantia weed (Tradescantia fluminensis ). It is hoped biocontrol agents like the tradescantia stem beetle will breed and multiply in amongst the weed, living it off in the process.
It is too soon to know what impact the stem beetle will have here, but laboratory studies have shown that they can be extremely damaging to tradescantia. Few parasitoids (an organism that spends a significant portion of its life attached to or within a single host organism) are believed to occur in New Zealand that could attack this beetle. The effect of the tradescantia stem beetle should complement attack by the tradescantia leaf beetle and tradescantia tip beetle. The stem beetle is highly host-specific and it is highly unlikely that anything other than tradescantia will be attacked. A monitoring programme is in place to measure the effectiveness of the three beetle species.
The tradescantia stem beetle is native to south eastern Brazil and north eastern Argentina. It was first imported from Brazil by Landcare Research into containment for testing in 2009. Permission to release this beetle was granted by ERMA towards the middle of 2011, but releases were delayed because of the need to clear the beetle of a gut parasite. The first field releases began in February 2012 and will be continuing. This beetle has not been used as a biocontrol agent anywhere in the world before.
Photo: Bernard and Rose Hailes (covenantors/landowners), Jodie Denton (former Kaikoura District Council biodiversity officer, who made early Biodiversity Condition Fund applications for the project) and daughter Rosie, and local QEII regional representative, Miles Giller.