Thursday, August 11, 2016
Sights like this in the Wainui area have become increasingly common as the giant willow aphid becomes more entrenched in the Bay of Plenty. Photo submitted
BLACK soot covering willows around the Bay, caused by mould feeding off honeydew, could have flow-on effects for beekeeping, gardening and river bank erosion.
The honeydew is deposited on leaves and branches by the giant willow aphid.
Bay of Plenty Regional Council principal works engineer Tony Dunlop said the sight of black willow trees around the Bay had become the norm over the past two seasons.
“There were pockets of the aphid across the Bay a couple of years ago, but the mild winter this year seems to have allowed the aphid to spread. This is potentially a big issue for river edge protection works as the willow is a key tool for strengthening river banks against erosion,” he said.
The giant willow aphid, which measures five- to six-millimetres long, was first reported in Auckland in December 2013.
Poplar and Willow Research Trust general manager Ian McIvor said its spread had been rapid and the effect devastating.
“There is no evidence it harms the tree but we’ve not seen it as extensive as this season and the giant willow aphid so far into the winter period,” he said.
Willows were the only recognised host plant and the impact had been seen in ornamental and decorative trees in plants and gardens.
Wasps fed on the honey dew and the increased wasp numbers might be creating potential issues for members of the public with a higher risk of wasp stings.
If the tree health is harmed, there were also flow-on effects for the habitat and shade they provide for trout and eels, and the insects they feed on.
Beekeepers are also keeping an eye on the issue and carrying out their own research into possible solutions.
Bees harvest the honey dew, which can change the characteristics of honey, including raising its melting temperature, creating a grainy texture and causing discolouration.