Alligator weed found on eastern Bay farm

Bay of Plenty Regional Council staff are working with an eastern Bay of Plenty landowner to remove and control an infestation of the aggressive pest plant alligator weed from farmland near Taneatua.

Alligator weed (Alternanthera philoxeroides), an aquatic weed which also grows on land, was identified by the landowner aftereading about the weed being found in a Tauranga City Council wetland.

Bay of Plenty Regional Council Biosecurity Officer Des Pooley said the weed can grow easily from a small stem or fragment, and because of this it is often spread within and between waterways.

"It may well have been brought to the site as a result stock movement, or on contaminated machinery," Mr Pooley said.

He said if alligator weed establishes in the Bay of Plenty it could seriously impact on farming activities and block waterways.

"So we have to be very careful."

Mr Pooley said once the landowner contacted the regional council the property was inspected to confirm the infestation.

"Restrictions were immediately put in place to prevent it from spreading. This included fencing off the affected area and stopping stock from accessing the area."

“This latest incursion also serves as a reminder to landowners and contractors to ensure all farm machinery is clean before leaving a property,” Mr Pooley said.

A native of South America, alligator weed is easily recognised by its white, papery, clover-like flowers. Its leaves are shaped like teardrops and grow in tiers opposite each other along hollow stems. It is an aquatic perennial that forms dense floating mats on slow moving water bodies. It can hinder access to water bodies and increase the risk of flooding. As in this case, it may also establish as a land-based plant, invading pasture and cropping land. It can form a dense tangle of roots up to one metre deep.

Alligator weed is already widespread in Northland and has been discovered in Auckland and the Waikato. The Bay of Plenty hosts a handful of land-based sites, including one near Edgecumbe, all of which are under intensive long-term control programmes.

Mr Pooley said alligator weed is very difficult to control because of its extensive, deep root systems.

"We urge landowners and contractors to notify Bay of Plenty Regional Council immediately if they are suspicious of an unusual plant," he said.