Environment Waikato is working to control alligator weed in the lower Waikato River before it becomes a serious threat to the Region’s wetlands and waterways.
This week’s Biosecurity Committee heard the water weed poses a high potential risk to wetlands connected to the river, with 100 hectares of the lower river already infested. The accidentally introduced weed has spread to the river delta and several isolated sites in the Region.
It is an aquatic plant, although it can grow on land and has recently been found growing in some Hamilton lawns. It can form large floating mats in open water, tangled swards on the banks or low growing mats in pasture, clogging waterways, hindering drainage and boat access and excluding native plants. It is also poisonous to stock.
Alligator weed is now present on many of the river’s islands and in some drains in the Aka Aka and Otaua district, threatening wetlands, including the internationally recognised Whangamarino.
It has also been found in the oxidation ponds at Tuakau and on the beach at Kariotahi. Drainage maintenance was also helping to spread the weed.
Environment Waikato has accelerated a project to control the weed, spraying in December, February and March.
Landowners in the area were generally supportive, and a representative of the Huakina Trust had completed herbicide spray training so the Trust could assist. Control was done with both an airboat and helicopter as well as land based spraying.
The Committee was told controlling the weed would require a long term commitment and planning, as well as ongoing evaluation of progress.
Over the next few weeks more spraying would be done and the effects monitored now that distribution of the weed was better understood.
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