From old foes to newer arrivals that continually threaten our borders, weed control is ongoing and expensive. But until recently we’ve not known how much weeds cost the country.
A review, led by scientist John Sanders from Lincoln University, has looked at the cost of weeds to the farming and forestry sectors. The team focused on ten common pasture weeds; the total cost was estimated at $1,306 million a year, mostly due to lost production.
The three most costly weeds were Californian thistle, giant buttercup and yellow bristle grass, knocking out $1,171 million in production - not counting the cost of control.
Forestry has its own problems with weeds, mostly during the early stages of the production cycle when young trees are vulnerable to competition. Forestry weeds were estimated to cost the industry more than $333 million a year, with the main culprits including broom, buddlea, pampas grass and blackberry.
It’s important to know how much weeds cost, so we know where best to invest in their control and what research to prioritise.
While pest control represents a significant on-going problem for most farmers, scientists are working on biological controls to target some of our most troublesome weeds.
For example, Landcare Research is working on an insect biocontrol against horse tail, releasing weevils over the summer onto sites in the Manawatu. Horse tail is a plant that is problematic for a number of reasons. Its deep root system makes it hard to control with herbicide. It can spread through pieces of plant that get carried around on machinery, or in contaminated soil / gravel. It’s toxic to livestock. And its liking for wet conditions puts it in direct competition with native plants, causing riparian margins to be over-run, drains and streams to block.
Research into the impact and control of pests underpins the success of farming. Environmental weeds are also recognised as one of the main risks to native plants, especially threatened or naturally rare species. Federated Farmers is therefore very supportive of research efforts to understand the impact of weeds and come up with better ways to control them.
Dr Lisa Harper - Senior Policy Advisor, Federated Farmers