Efforts are being made to eradicate the region's wilding pines.
About 200,000ha of invasive wilding conifers are encroaching across Hawke's Bay and could have "devastating" economic and environmental effects.
The warning came yesterday from Local Government New Zealand's Regional Sector chairman, Stephen Woodhead, who claimed while the scourge was widespread, Hawke's Bay is "the worst affected North Island region".
"Wilding
conifers [also known as wilding pines] are an invasive pest tree affecting landscapes and pastoral productivity across New Zealand," Mr Woodhead said. "They are advancing exponentially across New Zealand - establishing dense stands around some of our most iconic tourist destinations, on farmland and on Crown land, and threatening our economy and environment on a number of levels. Wilding conifers are trees in places they are not supposed to be. They have been branded the number one pest in some regions."
Landcare Research said there are 10 main species that have become wildings including Lodgepole pine (Pinus contorta), Radiata pine (Pinus radiata), Douglas fir (Pseudotsuga species) and European larch (Larix decidua).
The organisation said because the trees grew in dense stands, and are not able to be managed as a plantation, they have "no economic value" for wood. Instead, wildings can reduce the value of pasture, displace native biodiversity, reduce water availability and alter the landscape.
