Horizons celebrates establishment of field horsetail weevil

Horizons environmental manager Craig Davey says the establishment of these weevils is another positive step towards managing field horsetail in our region.
 
“We identified they have survived the winter season by finding an adult weevil at the site alongside larvae within stems of field horsetail,” says Mr Davey.
 
“Using this weevil as a biocontrol agent is a first in the world for field horsetail .
 
“We are excited to have been part of the Rangitikei Horsetail Groups efforts to pave the way for managing field horsetail in Aotearoa New Zealand.
 
Mr Davey says this pest is a threat to the agricultural sector.
 
“Field horsetail invades pasture, spoils bailage and stock won’t graze it, it’s a real nuisance,” says Mr Davey.
 
“Field horsetail is a difficult pest plant to manage as methods such as removal or herbicide work for a short period of time.
 
“Herbicides aren’t effective against field horsetail because they don’t reach the full extent  the root system to properly kill the plant.
 
“Small root fragments can lead to a new population.
 
“Field horsetail is most commonly spread through contaminated gravel, and by water (e.g. flooding).
 
“It’s so persistent and tricky to control, leading to loss of productivity and increased pasture management costs on farmland .
 
“The good news is the weevils should help us manage the plant.
 
“Weevils bore into and feed inside the stem, which kills everything above them.
 
“The adults then lay eggs and the larvae once hatched eat down the stem through to the rhizomes (roots), which help to effectively kill the plant.
 
“We’d like to acknowledge Landcare Trust who facilitated the Rangitīkei Horsetail Group who have made this possible.
 
“Collaborating with this group has led to this wonderful outcome.
 
“They helped research all the options to manage field horsetail which is how we landed on the weevils.
 
“A special mention to Bioeconomy Science Institute Manaaki Whenua Landcare Research as part of this group who have also helped us on this journey and helped us confirm the establishment of the weevils.