An explosion in wasp numbers is being partly put down to one of the latest pests to get across the border - the giant willow aphid.
The aphid feeds on willow trees and causes them to weep sap, which is then eaten by the wasps.
One farmer says wasps have reached such crazy proportions on willow trees on his farm he can't go near them.
The giant willow aphid was first identified in Auckland in December. Four months later it had spread across the entire North Island and made it at least as far south as Ashburton.
Federated Farmers president Bruce Wills says while the Ministry for Primary Industries is now on the trail of the aphids it's way too late to make a difference.
Mr Wills says the wasps are a hazard for farmers and are also having an impact on honey production on his farm.
He says while ladybirds love eating aphids it will take years for their population to grow large enough to get the giant willow aphid under control.
The aphid has also been found on kiwifruit orchards recently and the industry says advice it has received suggests it is quite common for aphid numbers to reach very high numbers very quickly; then collapse again equally rapidly.