With much of the river protection work in our district reliant on willows, the arrival of the giant willow aphid could be an environmental disaster.
"When we were out duck shooting it was raining giant willow aphid excreta," Top Grass Rd dairy farmer Vince Payne said.
"We had parked our truck under the willows at Ngapaeruru for two days and it was absolutely showered in sugary water, the honey dew of the aphids."
Mr Payne said with a large amount of environmental work in this district carried out with willows, he has concerns.
"I've nine hectares of my 88ha in riparian plantings using willows, the first of which were planted in the 1970s.
The willows have done a great job in taming the shingle and the alluvial processes, with natives regenerating underneath. Willows are a great nursery species, but in the last year I've seen them dying."
First discovered in Auckland in December 2013, the giant willow aphid has spread rapidly and John Barrow, Tararua's representative on Horizons Regional Council, said there have been trees lost in our district.
"We've an awful lot of willows holding our rivers in place and there appears to be some trees which have died, whether they've been weakened by other causes and just finished off by the aphid, or whether it's simply willow aphid damage, it's unclear. It is a concern and if it becomes trouble we'll be trying to breed changed varieties."
Along the banks of the Raparapawai Stream on Mr Payne's farm, the black mould on some sections of the willows is the tell-tale sign of the giant willow aphid, while a gap where a willow has died also indicates the aphid's presence.
Walking in among the plantings, the ground beneath some willows is black, despite recent heavy rain, another sign of the aphid.
"I only noticed the die-back last year when we were carrying out our willow working bee," he said.
"There were large colonies of the aphid and while the willows are dormant at the moment and the colonies not so big, they are still here."
And cutting willow poles used for river protection left people with blood-red hands from the aphids.
"After cutting 1500 poles we certainly had blood on our hands," Mr Payne said.
"The riparian planting of streams with willows has been one of Horizons' absolute success stories and I'd hate to see them destroyed."
Hoping native birds will feed on the aphids, Mr Payne is also looking to resistant willow species.
"The Salix matsudana willow, one of our most prominent willows, is where we could see the most deaths. There are willow species which so far continue to be resistant, but we all need to keep looking closer at our plantings."
Mr Barrow said a secondary problem is that the willow aphid's honey dew attracts wasps.
"This is a very new pest and we're not sure of all the consequences," he said.