A world-first biocontrol agent is going to fight a wandering pest
Tradescantia, also known as wandering jew and wandering willie, is an insidious weed that is hard to control. It quickly takes over gardens and reserves, and is known to give dogs dermatitis.
Any scrap left behind can re-sprout. It thrives in shade, in damp conditions, and in most soil types. Its leaves form large, dense mats that prevent native species regenerating.
But there’s new hope for controlling it in NZ with the world’s first field release of the tradescantia yellow leaf spot fungus in Rotorua.
Chantal Probst of Manaaki Whenua Landcare Research says the yellow leaf spot fungus has been extensively tested and is host specific. That means it’s highly unlikely to attack any other NZ plant life.
It works by infecting the weed and damaging the epidermis, causing the leaves to shrivel and die. It is ‘released’ via the planting of lab-infected plants among healthy tradescantia plants.
Dr Probst says it’s hard to determine how long it will take for the fungus to become properly established as it is the first time it has been released in any country as a biocontrol agent.
The fungus was approved for use in 2013, but it was not imported until three species of tradescantia-eating beetles were first given time to establish. The beetles have shown great promise, but struggle in areas that flood, a popular growing area for tradescantia.
The fungus will initially be released into areas without any beetles. In future, it’s expected the beetles and fungus will complement each other. A monitoring project has been set up to measure their effectiveness.