The velvetleaf pest remains a very real risk to the success of Kiwi farmers' crops, according to the Ministry for Primary Industries (MPI).
The warning comes just two days after the Waikato Regional Council stepped up its response after a marked increase in what they describe as "one of the world's most invasive pests".
The plant is dangerous because it competes with arable crops for space, water and nutrients, and is listed as an "unwanted organism" under New Zealand's Biosecurity Act.
Farmers who have planted fodder beet crops are being asked to be particularly vigilant, as some lines of the crop are believed to have been contaminated with velvetleaf seed.
However Waikato Regional Council's Wendy Valois believes fodder beet are not the only crops at risk -- and says the increased threat of velvetleaf also appears to be related to the movement of infested maize or maize silage.
Those maize infestations have been spotted throughout the Waikato region, and are particularly prominent in the North Waikato, Matamata-Piako and South Waikato districts.
MPI velvetleaf response manager Carolyn Bleach says the pest is particularly bothersome because some crops that have already been inspected have now been shown to have become infested with velvetleaf plants.
"It's become apparent that velvetleaf shoots up dramatically when it goes to seed," she said.
"A plant that may have been hidden by the canopy of the crop one week can appear a week or so later."
Dr Bleach says there have been 169 confirmed cases of the weed in 11 regions throughout New Zealand -- and it appears farmers in Canterbury are the worst affected, with 88 confirmed cases in the area.