The first biological controls aimed at kerbing woolly nightshade growth were set loose in a Welcome Bay forestry block on Wednesday.
Lace bugs eat woolly nightshade leaves and have a 40 day breeding cycle.
“The females can lay something like 900 eggs,” says Bay of Plenty Regional Council senior pest plant officer John Mather.
Once they are established on the underside of woolly nightshade leaves in the Welcome Bay block, pest plant officers will begin transferring lace bugs to other substantial woolly nightshade growths, says John. Lace bugs do fly, but not very far.
“The biological agent won't eradicate the plant,” says John. “Ultimately what we hope to happen is that the lace bugs will reduce the vigour, we will see hopefully, a lot of leaves yellowing off and falling from the plant – and ultimately young plants may not survive.”
John Mather, Rehua Smallman, Des Heke & Warwick Murray inspect the scene.
The lace bugs are from Brazil, the home of woolly nightshade, and they eat the leaves.
There's no eradication achieved through biological control agents, but they are expected to slow the plants down, and perhaps divert plant energy from seed production to survival.
The lace bugs are initially going to be released in Welcome Bay. Their release is the culmination of 10 years of research, and their importation is approved by the Environmental Risk Management Agency.
“Outside of that area we still require people to control woolly nightshade, which is a very problematic plant,” says John.
“The bio control agent is a tool which will assist us in the control of woolly nightshade, which is an aggressively fast spreading weed that we do not want people to give up on in the lightly infested areas.”
John says an application is to be made soon to import a second biological control agent for woolly nightshade, a flower feeding weevil.
“If Land Care Research gets permission, they will be lodging an application to import them, and we will have an insect that attacks the leaves and general vigour of the plant, and an insect that attacks the flowers, which will hopefully diminish the seed production. Less seed production and less vigorous plants could be hugely helpful for us.”