There have been fresh outbreaks of some invasive weeds in parts of the North Island, posing a threat to farmland and crops.
One weed, velvetleaf - considered one of the United States' worst plant pests - has been found in a Waikato maize crop.
First discovered in New Zealand in the late 1970s and eradicated, it has been identified at Waihou, growing both in the maize crop and along fence lines.
The Foundation for Arable Research is keen to take an aggressive stance to control the weed, which can reduce maize crops by up to 35% and could cost the grain industry millions of dollars to control.
Another plant pest, tutsan, which can cause significant damage to pasture, is also becoming a major problem in Waikato.
The regional council says it is finding pockets of tutsan between Taumarunui and Ruapehu near the regional border.
It is urging all landowners to be on the lookout for the semi-evergreen shrub with yellow flowers and round red berries.
Alligator weed breakout
In neighbouring Bay of Plenty, local authorities are working to control a fresh outbreak of the aggressive plant pest alligator weed in a Tauranga wetland.
The regional council warns that if it became established in the region, it could seriously disrupt farming activities and block waterways.
Alligator weed is already widespread in Northland and has also been found in Auckland and Waikato.