The two properties known to be affected by velveltleaf within the Wellington region are in South Wairarapa, one in Pirinoa with 6.8ha of fodder beet and the other in Hinakura with 6.2ha.
GWRC biosecurity manager Davor Bejakovich said three flowering and seeding plants were found and removed at the two sites.
"The plants were bagged to prevent any further seed fall, removed from the site and sent to the landfill for safe disposal," he said.
"The three sites have been marked with GPS and biosecurity staff are working with the landowners to manage the future risk at these sites.
"Because of the likelihood that viable seeds have fallen, these sites will require ongoing monitoring and management."
A recent report to the GWRC Environment Committee said velvetleaf may be considered for inclusion in the review and development of the Regional Pest Management Plan (RPMP), subject to the national decision regarding long-term management options.
The Ministry for Primary Industries has put an alert out to other farmers who have planted fodder beet seed this season to check their crops. Farm, crop and machinery hygiene are important strategies for the prevention and control of velvetleaf and all sightings of the weed should be reported immediately to MPI on 0800 80 99 66.