Canker threatens apple orchards

PETER WATSON
Last updated 11:40 21/08/2012
canker
PATRICK HAMILTON/FAIRFAX NZ
CANKER CONTROL: Simon Easton inspects a tree on his Mariri orchard which has had european canker cut out.

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Like a cancer, european canker is quietly causing carnage in many pipfruit orchards.

Already, tens of thousands of trees - including whole blocks - have been ripped out over the last year or so. Hundreds of thousands of others have become infected with the fungal disease that has no cure.

It has been likened to a smaller version of the Psa-V scourge that has devastated kiwifruit orchards in the Bay of Plenty.

Few pipfruit orchards have no european canker, although it is particularly bad around Riwaka, Lower Moutere and in high-rainfall and windy areas.

It has been around for decades but has exploded after several wet seasons and is spreading so rapidly that orchardists have asked the Tasman District Council and Nelson City Council to declare it a boundary control pest.

Its alarming march has been aided by grower complacency and poverty, the closer plantings of dwarf trees in many new orchards and infected seedlings from nurseries.

And it comes at the worst possible time for growers, many of whom are struggling to survive after three consecutive years of losses. Deep in debt, they lack the cashflow to devote to the extra spraying and relentless tree surgery required to keep the disease under some kind of control. Nor can the most vulnerable afford to replace trees they pull out, further reducing their income.

Efforts to curb the disease are being compromised by owners who either cannot or will not take steps to properly manage their own orchards or have bought them for redeveloping. This "growing to extinction" approach is jeopardising the work being done by responsible orchardists.

Simon Easton knows first hand the damage european canker can do.

The Mariri orchardist and chairman of the Motueka Fruitgrowers Association has had to pull out three hectares of infected trees this year on a block leased by his family and next year they will get rid of more.

He says the soul-destroying task is the toughest thing he has had to do in 17 years of orcharding.

He is not alone.

He personally knows of six or seven growers who have had to pull out whole blocks, some which were only planted three years ago. Intensive plantings of jazz, envy and royal gala have been the worst affected, while fuji and pink lady have shown more tolerance, although no variety has been spared. Trees typically take from six months to five years to die.

"It's the No 1 problem in the orchard," he says.

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It is so bad in hot spots like Riwaka there is no point in planting any more trees because of the amount of infection, he adds. Some growers there had hired gangs who spent all their time on canker control in a bid to save their own trees.

However, it it is an uphill battle, he says.

"The majority of growers are walking their orchards [to check for canker] three or four times a year and more on some bad blocks. The really bad blocks are being pulled out even though they may still be producing okay because they are a huge source of inoculum."

But some growers are not either being ruthless enough or do not want to know, he says. "They have got a block that is stuffed but is still producing okay so they are not doing anything.

"If I had that person on my boundary I would be tempted to get a bulldozer to sort it out," a frustrated Mr Easton says.

"Most growers want to do something about it but financially they can't afford to put in new trees so it's tough for them, but morally they have got to start taking their trees out."

Mr Easton says the disease is now showing up on the Waimea Plains where growers have taken early action, and he fears what the spring may bring.

"Everybody is nervously waiting to see what the effects of the autumn have been. If we get wet, stormy conditions, the spores go ballistic and spread for kilometres.

"Last year we had the perfect storm and the disease said ‘who's your daddy'."

It had not helped that growers had routinely left piles of infectious canker cuttings in the orchard rather than burn them and that many of the trees planted in recent years had proved very susceptible to canker, he says.

"When people were clamouring for trees, I think there were some poor budwood selections and people were taking budwood off trees which already had canker."

Mr Easton says it is difficult for nurseries, as the disease could lie dormant for several year, but infected seedlings had been a widespread problem. Nurseries had since introduced a code of practice.

The disease has already had a significant economic impact, he says.

Canker control cost up to $1 a carton of fruit, then there is the loss of income if trees are pulled out.

"Imagine you have a block of 3000 trees and you take out 300, that's 300 cartons and that's $6000."

It is another "kick in the guts" for beleaguered growers, he says. "When you thought it couldn't get worse, this starts killing our orchards."

It has also proved costly for nurserymen such as Sid Lambert of Lambourne Marketing who says business is suffering because growers cannot afford replacement trees even though canker is running "absolutely rampant".

"They call Motueka and Riwaka the black forest and it's moving pretty rapidly onto the Waimea Plains.

"I've been in this industry for 30 years and I've never seen it this bad."

He was treating all budwood by soaking it for several days "in a bath of chemicals" to eradicate it.

However, the disease has provided work for contractors such as Neil Jackson of Motueka, who has pulled out blocks as big as 5ha and is regularly asked to take "bits and pieces" out of others.

"We have been carting cuttings off trees where canker has been cut out and taking it away for burning. We did a little last year and quite a lot this year. It never used to happen."

Consultant Greg Dryden of Fruition Horticulture says what makes european canker so damaging is its ability to spread very quickly.

One canker can multiply into 400 in four years and there is no silver bullet, he says. A cocktail of fungicides - the most effective being copper and captan - can control it but nothing kills it.

Regular spraying needs to be matched by the "religious removal" of canker from trees throughout the year, and the infected deadwood burnt.

However, until recently it had been treated too casually.

"Complacency is a harsh word, but it is something that went off the radar because of low levels of infection and it got away on growers. Hindsight is a wonderful thing but we should have been more rigorous in removing it.

"It's the Psa of Nelson. It's not quite as bad as Psa but if we get another bad autumn it has the potential to be.

"Growers are working hard to control it but at the moment we are behind the eight-ball."

Pipfruit NZ technical director Mike Butcher defends the industry's response, saying it has put a lot of effort into giving growers the tools to fight a disease which is proving "extremely difficult to control" because of wetter-than-normal weather.

It had published a management strategy last year, brought in an expert from Holland, held workshops and field days and devoted two sessions at this month's annual conference in Nelson to it, he says.

"There is huge awareness of it and how it needs to be dealt with."

However, he concedes that some growers are struggling to cope and that others with a "farming to extinction mentality are making it very difficult for their neighbours".

He holds out hope that the move by local councils to make european canker a boundary control pest will help bring them into line.

TDC biosecurity co-ordinator Lindsay Vaughan says under its revised regional pest management strategy, which is expected to be adopted shortly, orchard owners will have to control canker to the recognised industry standard within 30m of an adjoining orchard. If they did not, they would have to pay the cost of getting a contractor in to do the work.

To prevent personality conflicts and petty boundary squabbles, the complainant will have to pay for an independent inspection to prove the orchard is substandard.

It is, he says, a sensible way to protect the more vigilant and industrious orchardists, and one that is used for other major pipfruit pests such as fireblight, black spot, codling moth and powdery mildew.

WHAT IS EUROPEAN CANKER? It is a fungal disease that thrives in wet conditions and is spread by rain, wind and even air blast sprayers. Canker spores enter the tree mainly through fresh scars caused by leaf fall. It can also happen at bud break, petal fall and during harvesting. Pruning wounds are another site of infection. Cankers are generally slow acting, but can encircle infected branches, causing shoot dieback and will eventually kill the tree. They significantly reduces crop production, although not fruit quality.

- Nelson

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