Leaf-sucker on nightshade duties

A South American bug that sucks the leaves of woolly nightshade is to be released in Taranaki to see if it thrives in this region and can effectively control the pest plant.

The Taranaki Regional Council is planning three releases of the lacebug, which has already been released in Bay of Plenty following Environmental Risk Management Authority approval for its use.

It will be released at two sites in North Taranaki and one in South Taranaki.

"It's been well established that the lacebug is host-specific and will not affect any other plant life or animal life," says the Taranaki Regional Council's Compliance Manager, Bruce Pope. "We're keen to see if it is effective in Taranaki conditions."

The lacebug feeds on the leaves of woolly nightshade, puncturing the surface and sucking out the green layers beneath. As the leaves dry out, plant growth is stunted and flowering and fruit production are reduced. In severe attacks, the plants may die.

"It's an opportunity to take a long-term approach to control," says Mr Pope. "The Pest Plant Management Strategy for Taranaki classifies woolly nightshade as a surveillance plant rather than an eradication plant, so there is no short-term pressure to remove it. We'll watch the lacebug closely and it it's showing good results within a year or two, we'll consider releasing it at other sites or taking measures to encourage the natural spread of the bug."

He says biological control is preferable to chemical control or physical removal in some areas because only the target plant is affected. "That's why two high-value biodiversity sites are among our three release areas here in Taranaki." The lacebug is also a good option on or near organic properties.

He says ERMA's approval for lacebugs followed rigorous research and testing by Landcare Research, which is supplying lacebugs for the Taranaki releases.

Lacebugs caused extensive defoliation of woolly nightshade at a South African release site in 2007, causing the death of plants from seedlings to large trees. They were also found to be surprisingly cold-tolerant, despite their South American origins.