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Published: 2008-03-27 00:00:00

Environment Waikato’s alligator weed eradication programme has been praised by a leading aquatic pest plant expert.

Alligator weed – one of the world’s worst weeds – is described as the Waikato’s greatest weed threat. The cost of its control takes up a significant chunk of the council’s biosecurity budget and Environment Waikato’s operations have helped contain it to fewer than 50 infestations in the region, spread over an estimated 200ha.

By contrast, alligator weed is now rampant in Northland, blocking waterways and damaging dairying and horticultural productivity. Northland has no direct control programme in place and landowners are not required to do anything about the weed. In the Waikato it is deemed an “eradication pest plant”, meaning the regional council actively seeks to get rid of it.

In a report to be presented to the council’s regional pest management committee meeting on Monday, Paul Champion from the National Institute of Water and Atmospheric Research says Environment Waikato’s targeted eradication programme is making “good progress”.

Success was due to a range of factors including experienced programme staff, enough funding to allow eradication at newly discovered infestation sites and a resource consent allowing herbicide use.

Dr Champion recommends a number of extra measures, including purchase of a motorised knapsack sprayer to help manage weeds at Waikato River sites, and three-times-a-year treatment at these sites.

“Any reduction to the current programme would severely increase the risk of alligator weed spread and [subsequently increase] impacts and costs to affected parties.”

Meanwhile, Environment Waikato biosecurity officer Wendy Mead said the Trade Me website had followed up with an advertiser who was offering Waikato farmers alligator weed-infected silage for sale during the region’s drought. The advertiser had been reminded by Trade Me that it was illegal to knowingly spread alligator weed in New Zealand. The ad was withdrawn some time ago.

Also, a Hauraki farmer had contacted Environment Waikato about a load of silage imported from Northland - checks showed the silage was full of alligator weed and the person who sold it was required to take it back to Northland.

“These incidents again underline how important it is for Waikato farmers to be very careful about the type of imported feed they buy. As NIWA’s Dr Champion suggests, we in the Waikato have to remain very vigilant if we want to prevent this nasty and economically damaging weed from getting a further foothold in our region.”