Pest Plants and Animals at Redwood Forest

August 2013

Pest infested wasteland has been converted into a productive Redwood forest

Turning a weed and pest infested wasteland into a productive forest.

General Manager of The NZ Redwood Company, Simon Rapley started with the company in 2006. The company initially bought the 4125ha Conway Hills land in 2001 after it had been on the market for some time because of its condition. During WW2 the property owners, with a shortage of labour, rapidly lost control of the broom problem and subsequently were not able to get back on top of it. "The neighbour reckons no-one has ever made a profit on the farm and he wished me luck. I almost thought this property was going to be impossible to fix."

Hundalee Forest has 1540ha of planted redwoods which will be merchantable in 30 years, but 40 years might be the optimum time for them to be harvested at a higher value. Harvest is likely to start when the trees reach 35 years. The forest also has 665ha of Douglas fir trees.

The NZ Redwood Company is owned by Californian family company Soper Wheeler. It initially bought six farms in New Zealand and now grows trees at Hundalee, 300ha at another site in North Canterbury and 650ha at Hunterville.

Redwood timber is worth twice as much as pine or Douglas fir. It is appearance grade wood and always used on display for weatherboards, decking or internal panelling. It is very stable and it doesn't warp, twist or crack. It is not ground durable but it is durable enough to be out in the weather. Heartwood is a nice red brown colour, and sapwood is white.

Redwoods grow slower than pine trees but faster than Douglas fir however on a good North Island site they will grow faster than a pine tree. Simon says they take a lot of care and don't tolerate weed competition. Other trees will grow with neglect, but redwoods wont, and they take a lot of inputs. They are a huge challenge to grow.

Broom is a legume and it produces a huge number of seeds per ha. Seeds will last more than 100 years in the soil once broom and gorse is established on a piece of land. Simon says "Forestry is pretty much your only option because the shade from the trees will suppress the broom later."

Mature gorse and broom plants grow up to three meters tall and can be sprayed and burnt or crushed and raked off with machinery. "We did all those things, and broom will still come away like a lawn, there will be that many plants. There are also chemical options for controlling broom when it is very small. Once the plant gets to knee high there is nothing you can kill the broom with that can also be sprayed over the top of redwood trees. We have spent more than a million dollars putting chemical on the broom over a number of years. However pines are proving a better tree to use with broom, because some chemicals which control broom can also be sprayed over pines without affecting them.

Without question, broom is the worst weed. It grows so fast. My advice to farmers who have a large area of broom is to jump on it. If they let any plants flower they will lose that land from production. It will be swallowed up in no time. There are biological controls but really the most that landowners can hope for is that the biological controls slow down the growth and spread of the broom."

Simon's theory is that the pigs spread the broom around. Birds like quail will eat broom seeds, but stones in their crop grind up the seeds. When pigs eat broom seeds, the seeds pass straight through them. "I have picked up a lot of pig poo and put it in a bucket of water, and mashed it up and found seeds. That's the way broom spreads on clear country because naturally it doesn't spread very far: the pods dry out and burst, and the seeds only spread a couple of meters. We are seeing broom establish several hundred metres from the closest bush, and quite often there are a cluster of plants, so I think it has come from pig poo.

Pigs are a big problem here. Two stations, one on each side of us, have been bought for hunting blooks. So pigs have been spreading out of these properties. And the pigs will be taking broom seed from here back into those properties too.

One of my first jobs was to put up a boundary fence between us and the neighbouring property. I thought a fence would keep out the pigs but pig hunters chasing pigs have found the pigs run straight through the deer netting. They just charge it and hit it with enough force that they spread the wires, and there is no stopping them.

I've had a few sleepless nights about the pests and weeds here. The redwoods will eventually overtop the broom. Snow is really good for the trees, because it flattens the broom, creates openings with more light and lets the trees come through.

We now have our own Hundalee Hog Hunters Club, with public liability insurance, radios and rosters, who hunt the block systematically. We know every area of the property is hunted at least monthly. We used to see pigs running up and down the roads. The Hog Hunters get all kitted out and crawl through the bush hunting the pigs. They are very well set up and experienced hunters, and they have drastically reduced pig numbers."

Simon says there are huge populations of German wasps in the forest.They live in the beech forest where they feed on the honeydew.

In midsummer they switch from feeding on sugars on the honeydew to feeding on protein but Simon is reluctant to put out baits which might also kill the bees. He says they spike mince with a poison, and use only very small amounts. "Its better if the wasps fight over it, and they take the poisoned meat back into their nest. If they are poisoned and die in the nest you can wipe out a large population.

We poison wasps for the equivalent of two or three weeks a year; there is a fairly short window of opportunity. We still have an area at the northern end of the property with wasps which have not yet been controlled.

I have been out and heard big cicadas nearly two inches long making distress calls, and looked down on the ground to see them being killed by wasps. Wasps will also kill chicks in bird nests and wipe out insect populations as they hunt for protein."

There is also a population of goats, "but we have hammered them, shooting them from helicopters and the ground. We have a specialised hunter come in who is a DoC manager from Kaikoura and he has trained goat dogs. He has been mopping up the remaining goats. The cost of getting rid of the last one is pretty high but we shoot them whenever we get a chance."