A ''double whammy'' of guava moth and a new strain of fungus is devastating Kerikeri feijoa orchards with some growers losing 95 per cent of their crop.

Feijoa Growers Association president Roger Matthews said the anthracnose fungus usually affected only ripe fruit.

However, a more aggressive strain was now affecting Kerikeri orchards.

The new form attacked unripe fruit, even when they were just 5-6mm long, and caused fruit to drop before it was ripe.

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In some cases the fungus was also causing die-back of branches and whole trees.

A feijoa affected by anthracnose fungus, which is destroying the crop in Northland. Photo / Stuart Duff
A feijoa affected by anthracnose fungus, which is destroying the crop in Northland. Photo / Stuart Duff

''Some growers in Kerikeri are getting 95 per cent fruit drop, it's just devastating,'' Matthews said.

Growers were sure it was a new strain but scientists had found its DNA was identical to a fungus seen as far back as 2003, so more work was needed to understand it.

A $356,000 Ministry for Primary Industries grant would help develop a control programme but Matthews feared a solution might come too late for some.

Sprays existed which might kill the fungus but it was not yet known which one was most effective, and none had been approved for use on feijoas.

''For the guys up there [in Kerikeri] the only treatment is to rip out every tree and burn it. I've heard that some feijoa growers are exiting the industry — if your whole orchard is feijoas and you have to rip them all out, that's business-ending.''

Badly affected growers included Peter Jack at Kapiro, who had been working hard to get on top of the guava moth problem affecting feijoas and other fruit.

''So it's devastating for him to now get hammered by this.''

Even if the fungus could be eradicated from orchards, they could be easily re-infected by spores carried on the wind from feijoa trees found in almost every Kerikeri backyard.

Matthews said his only glimmer of hope was that some of the 30 commercial varieties might be less susceptible than others, in the same way that some varieties of kiwifruit proved better able to withstand PSA.

So far only Kerikeri appeared to be affected by the new fungus, Matthews said.

''My hope is that it's because of the microclimate of Kerikeri with its semi-tropical rain and high humidity, but only time will tell if that's the reality or wishful thinking.''

While the fungus could make it difficult to grow feijoas commercially in humid areas like Northland he did not believe it would spell the end of the popular fruit.

With climate change, however, all bets were off.

Feijoas were grown commercially from Northland to Canterbury, with the biggest orchards around Gisborne. New Zealand had about 250 growers with 200ha in commercial production.

Matthews said it seemed unfair that farmers affected by the disease M bovis were compensated if their herds had to be culled, but there was no compensation for growers who had to pull up their trees.

Stuart Duff in what's left of his feijoa orchard near Kerikeri. Photo / Peter de Graaf
Stuart Duff in what's left of his feijoa orchard near Kerikeri. Photo / Peter de Graaf

"I'm bloody worried"

Things were looking good for feijoa grower Stuart Duff and his wife Paula.

Three years ago they harvested 14 tonnes of fruit from their 1180 trees at Kapiro, just north of Kerikeri, and were expecting to hit 20 tonnes the following year.

Instead they collected a measly 3.5 tonnes; this year they didn't even hit 1 tonne.

The reason is a virulent new strain of anthracnose fungus which attacks the fruit while still small, covering them in dark blotches and making them fall prematurely from the tree.

Eventually the fungus gets into the roots and the whole tree starts dying.

After pulling out hundreds of infected trees Duff now has just 600 left.

It was especially heartbreaking for his wife, who had worked hard for nine years to build up the orchard.

Duff said it was easier for him because he had lost everything once before when he had to flee Zimbabwe with only a few hundred dollars in his pocket.

Feijoa grower Stuart Duff with a few of his surviving fruit. Photo / Peter de Graaf
Feijoa grower Stuart Duff with a few of his surviving fruit. Photo / Peter de Graaf

He recognised the disease straight away because anthracnose had attacked his tobacco crop when he was farming in Africa.

To make ends meet his wife was now working in a packhouse and growing orchids while he was building trailers.

They planned to give their remaining feijoas one more try next season before possibly pulling out the lot.

Duff said the only answer was to develop varieties of feijoa that were not susceptible to the fungus.

''I'm bloody worried for the feijoa industry in New Zealand, I really am.''