NEW Zealand is losing the war on weeds, challenging our position as a global leader in biosecurity, warns Lincoln University professor of plant biosecurity Philip Hulme.
“Unfortunately, we have rather little to show for the vast amount of time and effort the Government and landowners invest in the management of weeds,” Hulme says.
The professor reviewed all the available literature and reports about weed control in NZ for a series of public lectures around the country, which he was required to give when he won the Leonard Cockayne Award from the Royal Society of New Zealand.
“I dug into the literature, the old reports, regional council information and DOC and MPI datasets to try to build the first comprehensive picture of the trends in weeds in NZ, the impacts they might be having and at the end of the day, how well are we actually responding to controlling them,” he says.
Hulme says the information is publicly available, but you need to know where to find it.
What he discovered is that for a variety of reasons, weeds seem to be winning the battle despite the millions of dollars being spent trying to control them.
Hulme breaks the problem into two areas: weeds that pose a threat to agricultural production and those which are an environmental threat.
He says two high-profile weeds which have arrived in the country relatively recently – blackgrass and velvetleaf – could affect agricultural exports.
“Blackgrass is a really nasty weed because it has a propensity to out-compete the crop, but also it’s known to become herbicide resistant quite quickly, and if you’ve got an oversized competitor in your cropping system, it becomes much harder to manage that sustainably,” he says.
Blackgrass has been detected coming into NZ often but worse than that, Hulme says, is that it has also been found in seed for export.
“There’ve been two or three incursions and the most recent detection was in seeds for export, suggesting it’s been in the country for a while and produced seed in crops so that’s a worrying sign,” he says.
“MPI have done a trace-back to try to figure out where the seeds might be coming from, then monitored those fields to figure out whether they can get rid of it. But there’ve been several occasions these seeds have been coming in over the past 10 years, which suggests it’s slipping through the border somehow,” he says.
Velvetleaf is a serious cropping pest and has been found in fodder beet and maize crops throughout NZ, particularly in Southland. It appears to have come in imported pelletised seed.
“They hadn’t really thought about other material that might be in those pellets. They came from Italy where velvetleaf is quite widespread,” he says
“The seeds were harvested, there was no significant cleaning of the seeds before they were pelletised and the contaminants were encased in the pellets that were brought to New Zealand, and it’s still a problem.”
Hulme says the biggest risk to the environment comes from seeds escaping from domestic gardens.
“There are likely to be new weeds appearing over the next 10 to 20 years that we haven’t got records for in the country,” he says.
“People might be growing more succulents because they want low-water gardens so there might be a whole heap of succulents that we don’t know from South Africa or other parts of the world that are a potential risk.
“If they get shared or someone decides to throw them over the garden fence, there is a risk those species will become established in the wild.”
In the wild, those plants could displace native species, much as is already happening with wilding pines in much of NZ.
He says the main reason weeds are getting away from us, is the lack of a coordinated national strategy.
“Regional councils are great because they have a regional focus and they can do things but for weeds, you need to have a national focus because if Marlborough aren’t controlling a particular weed but Canterbury is, it doesn’t make sense,” he says.
“If they’ve got a weed but don’t see it as a priority but Canterbury does, no matter what Canterbury does, the weeds are going to come from Marlborough at some point.”
Hulme says there’s not enough communication between the various agencies with responsibility for weed control.
“MPI probably don’t liaise as well as they should with the regional councils, regional councils don’t really talk that well to DOC (Department of Conservation), DOC and regional councils don’t talk to the city councils – and probably nobody talks to the landowners as much as they should,” he says.
“You have this lack of communication so the governance of the whole problem is flawed and so no one’s really working as a team, they’re all working in a piecemeal fashion and what happens is the resources we’re investing in controlling these weeds are being used ineffectively.”
Hulme says NZ’s response to covid-19 shows that if there’s enough willpower and a clear message we can succeed but weeds are always low in the list of priorities.
“People will always invest more on things like Mycoplasma bovis than they would in velvetleaf, but for a fraction of the money you spend on M bovis, you could have got rid of velvetleaf in the South Island and yet no-one sits down and weighs those things up,” he says.
“It’s now less about what herbicide we use and the application rates, but much more about the governance issue, about how we manage these problems and how we work effectively as NZ Inc as opposed to individuals or separate parts of the Government.”
