Angus Kebbell investigates how the wilding pine weed is being tackled, the challenges, and the paths to successful control

Angus Kebbell investigates how the wilding pine weed is being tackled, the challenges, and the paths to successful control
Wilding pine infestation

Wilding pines are consuming more country each year and farmers are struggling to keep them under control, so how do we address the issue and who is responsible?

The Hanmer radiata forest in North Canterbury, which was planted in 1901 by the Government, has largely contributed to the wilding pine problem through the North Canterbury high country. That was generated in an earlier time when someone else thought planting a billion trees was a good idea.

The northwest wind spreads the pines far and wide, so what responsibility does the Government have to support farmers more in the control of wilding pines? One could argue they have a considerable obligation, you could also argue that commercial foresters also have a responsibility to do more to control what is essentially their waste.

Some think farmers could do more through their grazing systems and if their stocking rates are high enough livestock will control wilding pines. This is an interesting idea but the reality might be different, or should wilding pines be treated in the same way we treat Nassella Tussock where the responsibility sits heavily on the farmer?


This week on Factum-Agri I talk with former Lincoln University senior lecturer for Plant Science, Dick Lucas and farmer Hamish Galletly to get their thoughts on the issue of wilding pines.

Farmers have been fighting a losing battle for years trying to control the problem. Manual culling has been a losing fight - the pines are winning.

But new approaches and new funding, including the use of blanket spraying and controlled burning have proven successful.

But after that the key is grazing intensity, and a rate of at least four stock units per hectare is required to keep the gains. However that is tough to achieve or maintain on low fertility soils. It is these areas that are especially vulverable and expensive to manage, made more challenging because to do so is largely uneconomic in a farming situation. But taxpayers are quite prepared to do that in the Department of Conservation estate given there is no economic constraint.

In the end, soil fertility is the prerequisite for sustainable farm control of wilding pines.

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Angus Kebbell is the Producer at Tailwind Media. You can contact him here.

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"But after that the key is grazing intensity, and a rate of at least four stock units per hectare is required to keep the gains. However that is tough to achieve or maintain on low fertility soils." What kind of dumb advice is that? That sort of stocking rate will just totally degrade the landscape! Livestock farming is becoming unsustainable on marginal land. What's the plan for when this land is permanently destocked and the soil stripped of nutrients and any native vegetation?

Perhaps the mean for a short rotation, I don't think anyone would suggest 4 su per Ha longterm. I.e the livestock eat and trample the pines once or twice a year .

There aren't many (if any) livestock class that will willingly eat pine and to be densely stocked enough to trample them the stock would totally destroy the terrain. Lets face it.. you can't breakfeed the high country. The only control method is "spray and burn".. very expensive (helicopters needed for both). The Govt clearly has an obligation and should front up. Maybe redirect some of the millions spent on upgrading walking tracks to tackle the problem.

Why not put slow growing natives in the area, outcompete the pines.

Unfortunately the pines would smother and outcompete the natives. A seedling pine can be 6ft in <3 years. After a burn, natives could be helisown which would be a good replacement but at the moment a lot of that high country is farmed so there'd be a big loss of grazing. The only way to deal with those wildings is "scorched earth" followed by pasture oversowing and then strategic native plantings.

Pines actually make a reasonable nursery cover for natives. you'd plant the natives and let the wilding pines grow, and shelter them . Abit of pruning and 30 years later you'd cut the wilding pines down , leaving 30 yo natives to grow.
But I think the issue here is that this is land that was never forested.

slorardb you're missing a pretty big point.. leave a wilding pine for 30 years and the landscape would be overrun. They are too scattered for normal viable management (pruning). They are an invasive pest weed and need to be treated as such. The land was forested originally with acclimatised native but successive waves of human intervention (both pre and post colonisation) destroyed the cover. The name Maniapoto actually translates to "plains of death" where vast fires were lit and the Moa were driven into killing zones. Then came European endeavours that cleared what was left for pastoral sheep farming. The area could and should be reverted to native forest but the pines have to be eradicated first.

Yes , after 30 years the pines would have formed a canopy , but youve planted the natives , and they are right underneath it . Its not a do nothing approach , it would require a fair bit of work . But not as much work as taking out the pines , then planting natives , then controlling the regrowth of pines competing with the natives you've planted.It works great with gorse, and I have seen it working with pines, just the clearfelling of pines destroys most of the natives as well . 25 years ago , we were allowed to go into pine plantations, wrench and remove native plants a week later , before clearfelling. We got some good Nikaus ( which were only 1 -2 metres high after 30 years)out of it , and some other natives. Doubt they could let the public do that today . but using the Pines as a nurse crop is a known technique. Last year i planted natives under gorse , and am pleased with the result, apart from rabbit damage . this year I'll partially clear the gorse to give the natives more light , but not take it out completely. i plan to leave most the gorse in .

The pines you're talking about are in a plantation setting, dense plantings compared to the wildings. We need to compare apples with apples. All the plantations I've walked through are pretty barren underneath, blackberry, some spindly light starved pittosporum, a few spindly ferns and deep layers of acidic needles. These are plantation forests next to native blocks so they don't seem to be much of a nursery for regen. After a good hot burn there isn't any regrowth of pine because the seed burden has been destroyed. Have a look at any pine to pasture conversion - no pines

I hope none of your gorse solardb is near a waterway. The new freshwater reg proposals were that gorse had to be removed/killed near any waterway because of the N leaching they cause. I haven't had a look at the final regs that came out recently, so stand to be corrected on that.

Its not . Havent heard of that rule , but the regional councils would be up for a huge bill if that was the case. And nzta and kiwirail.
I always thought the nitrogen gorse captured was stored in nodules on the roots , so hard to see it leaching.

As with all areas, the topography of the region isn't completely homogenous, it isn't a flat square area on a map. There are gorges, spurs, valleys, rivers, multiple altitudes, incursion boundaries, etc. Planting all of the fingers of topography that would naturally and historically have supported native flora and fauna populations that have been diminished by human use would be more effective than a rabbit proof fence/firewall catch net for invasive seeds. I'm from an area that is very similar to the North Canterbury highlands and observed this myself over many years.

fortunately there are some really good biological controls.

Interesting Aj.. wasn't aware of that. Where do I find out more?

pitch pine canker and pine beetle on google.

Radiata are nearly extinct in California due to these two.

All very useful Aj but none of those controls exist in NZ and there's no way approval would be given to import or establish them here so back to "scorched earth" IMO

Once upon a time NZ was the last to have rabbits free of haemorrhagic disease.
Not sure approval was ever given to import that, although if I remember rightly a bit of a blind eye was turned.

If you seriously think importing an uncontrollable biocontrol (legally or not) that would wreak havoc on our forestry industry ( remember it's all Pinus Radiata) is a good idea or should be considered as a control measure for wilding pines then I'm afraid you really need to reassess your position

It’s like saying let’s bring in foot and mouth to control feral stock.

Hell No, not at all.
I'm just pointing to a real live example where some farmer thought their need for some cheap/free rabbit control trumped the rules in place back then.
So that one was deliberate.
Then accidental importation of PSA to NZ kiwifruit.

Being this a direct result of forestry industry there should be a means they could compensate from their profits so this can be mitigated, a tax which would pay for all the costs of pest control maybe?

Unfortunately a lot of the problem stems from DoC plantings, probably most of the problem. Many of the pines (especially pinus contorta) were put in for erosion control and never managed. Tongariro is a classic example. The Tolaga Bay mess still hasn't been sorted because everyone involved is navel gazing as usual.. the council for not policing the consents, the forest owner saying "not us it was the harvesting contractor", the contractor saying "sorry it would bankrupt us and cost jobs", Meanwhile the local community and land owners are faced with devastation and an impossible clean up job with limited resources

and then this sort of thing at the end of the cycle...

The reality is this land cannot be farmed profitably. ID the boundaries to stop spread and farm around it. Manage the tree areas for carbon and timber that work and control the rest. People are doing this and are very profitable. We have this belief that it’s all animal farming and are slowly watching it slide away as profit falls to losses. We are going to have to accept change and manage it within the money available.

Only one fly in your ointment.. the boundaries have been ID'd and the pines are running over them. This isn't a profitable farming argument.. this is a stopping an invasive weed argument. If accepting change entails watching large chunks of the south island landscape disappear under pines then I'm all for the "slash and burn" option

Yes, it's an invasive weed problem. We just need an army of people to do the manual hard yards. To get that army we need to provide them with free accommodation and bus them to and fro around the territory. Pay has to be a lot better than the wage subsidy. Unlike many problems, this one needs people (as opposed to fossil fuel) energy. We should be embracing the task as one of our employment solutions.

Trouble with that solution Kate is it only targets the emergent trees. The seed bank is left to regen so it's a never ending task. Boomspraying with Helicopters is fast and effective and covers a large area quickly. Followed by burning gets rid of the dorment seeds and prevents regen. Providing free accomodation and buses will still only attract the few who are inclined to work outdoors in some quite unforgiving terrain and it's pretty expensive. IMO better to use those people to replant natives after the pines are gone and the tussock has regrown. They're using Helo's now to fly people into the more inaccessible spots anyway.

You're probably right - much the same basic argument as per the use of aerial 1080.

Yeah, and that has worked extremely well subduing rats, (and thus stoats) and possums in inaccessible areas. The same parameters apply - speed and efficacy, cost effectiveness.

Ah Jack...can't you hear the roar from the 'Areas of Outstanding Natural Beauty' proponents. Graeme Sidney paintings will be in the realm of 'once many years ago, the land looked like this...' Some South Island landscapes are sacrosant. ;-)

It's fair to say CO, the area looks significantly better under tussock than wilding pines so I kind of agree with the SNA proponents in this case and thus agree that some areas are sacrosanct

We're all falling over ourselves admiring the likes of "Boys Own" RocketLab, a completely useless endeavour, when we should be addressing far more urgent problems like tree-weeds, disposal of waste, creating and maintaining freshwater supply, et al ad infinitum.

This is pure sarcasm right??

Is this real? Who’s going to fund this list of things to do

You get what you manage for. If you're getting trees, you're managing for trees. Healthy grassland requires good grazing management, and likewise whatever forest type you desire needs to be worked at.
Without predators, which includes humans, to maintain tight herds ruminants spread out over the landscape. They become very selective where they graze, giving rise to both over-grazing in their preferred spots and over-resting in the shunned spots. These over-rested spots are then amenable to the establishment of woody vegetation.
The downside of spraying is the simplification of the soil life. Pines seem to thrive in compromised soils. As you spray you are making it fitter for pines. Next time out walking dig down in a native forest and compare that to what you see when digging in a pine plantation.

What you say is true maltwix but I'm not advocating returning the area to healthy pasture. Viable grazing is secondary to eradication of the pines. Spraying/burning/oversowing is the fastest most cost effective way of dealing with them.

The problem isn't that trees are growing, it,s the type of tree. Obviously they thrive there so spray it and replant with quality timber trees and there you go an asset. Why keep fighting to keep something looking a certain way just because that's the way some people perceive that's how it should look. Also farming animals on low fertility ground is a waste of effort and economically not viable. Ships will be carting logs out of NZ creating jobs and boosting export income isn't that what we need. You never know someone might even decide to build some sort of processing facility and there are some new emerging technology for different products eg bio plastics etc. wouldn't that be great.

Kate, whilst interesting that initiative wouldn't even make a dent in the spread. If you read the article the inventors are targeting production forests not wildings per sey

Hans the issue is simple.. wrong tree, wrong place. The scale of the problem is immense.. 90,000Ha/annum potential increase. The area these wildings infest is not an area that lends itself to production forestry, it's steep erodible difficult to access country. That's why a lot of these places were planted in the first place. As for farming, a lot of Merino wool is produced down there.. pretty reasonable returns for them. These pines can't be managed or processed at the required scale to deal with the problem

I work with a lot of areas with this etrees.
1. The Trees species are the problem - contorta, Corsican (planted by the Crown and early farmers who didn't realise the spread potential - no blame attached) which spreads like wild fire. Radiata is not a problem - very slow spread and very cheap and easy to control
2. Even once cleared in any form you have to keep going every year or so. No followup and it just takes off again. who will keep funding this?
3. Grazing on these areas doesn't pay - the reality is grazing is moving off more and more land because its uneconomic - some argue not but the market can't be beaten and we need to look at the hard facts. I see it on the land we manage in the real world along with many of the landowners.
Hans is right - to succeed we need to identify what areas are going stay in trees and manage them for timber and carbon to provide the income to control everything else. Species are changed over time etc. Its a bit like removing all deer - we tried very hard in the 70s and 80s and pushed numbers down very low but now with no economic value the numbers are exploding again. You need to have income coming in as at some stage the Government will stop the money and the whole cycle starts again. We have to learn to live with them and manage it from being a cost to at least a zero cost control and additional income for landowner as the old ways of making money off this land is gone.

Well some of your points have merit but some are mistaken. the deer industry in the 70s and 80s flourished due to an international market for velvet and the easiest way was feral capture. We can't manage the current crop of wildings for anything for two reasons. 1 they don't count for carbon credits because they don't fit the definition of a woodlot, same as shelterbelts don't. 2 they aren't any use for timber because a) they are the wrong species and b) they are unmanaged due the low density making management and harvest uneconomic. There is no alternative but to eradicate them - spray and burn extensively to reduce the problem. There is no viable return from these weeds in the short to medium term

With all respect
Im old enough to have been around in the venison recovery days and carried a fair few animals out.
Meat was worth money - yes velvet to but only for a month or so when in velvet. The point is an economic driver will get things done. No money in wild venison now so they breed - the population doubles on average every 3 years.
2. Many wilding areas are eligible for carbon - whether you are allowed to register them is another issue.
3. We have logged 100s of ha of wilding trees and made good money - the key is to convert it 2nd rotation to better trees that dont spread and manage them.

There are areas that are not economic to log or get carbon - these are the ones to remove but you need $$ and lots of it to do that and maintain it tree free -Im all in favour of removing these trees but we only have a limited amount of money so need to target it in the right place and try and get more money without relying on Governments which change all the time so we need to be pragmatic and not scorched earth one way or the other. The old saying "a stitch in time saves nine" is very relevant to controlling wilding trees.