The stock destroying pasture pest Chilean needle grass is beginning to raise its head and farmers are being advised to keep an eye out.
The grass is found in Canterbury, Marlborough and Hawkes' Bay, and is an invasive weed that in worst cases can cause blindness and even death in lambs.
Hurunui district councillor Vincent Daly said it could be present all year round, but it was easier to spot in summer months.
"Most of the year it just looks like any other grass...this time of year from now on to Christmas it runs up into seed head and the seed head is just like an arrow with a cork screw on the end and it just burrows into any stock hides and just goes straight into muscle, so if stock get it on them they just get condemned and they became value less really, it sort of just destroys your stock."
It can spread through stock movements, vehicles and people and councils are working together to find ways to stop it spreading, Mr Daly said.
AgResearch is also investigating what grasses can withstand the spray that is used to kill Chilean needle grass.
Farmers should contact their regional council if they find it, Mr Daly said.