Fear of frost used to chill Robin and Heather Nitschke's blood.
Since starting to grow tamarillos on their 4ha orchard on a northwestern slope at Whatitiri in 2007, they had tried everything to protect their plants against Whangarei's occasional severe winter chills.
Frost cloth, diesel burners, sprays and a wind machine all failed to stop the damage temperatures as low as -4C caused to their 6500 tamarillos.
"The expense of these measures and losses through damaged fruit probably cost us around $70,000 over the past five years," Mr Nitschke said.
Now a new mobile frost fan developed by Kim McAulay's Hastings company, Tow and Blow, is keeping the tamarillo orchard green when neighbouring land is covered by a white frost shroud.
The fan cost about $35,000 plus GST. As Mr Nitschke ruefully pointed out: "We could have bought two of these for what frost has cost us in the past."
But the Nitschkes are relieved to have finally found a solution to one of the major problems that has blighted their income since they quit managing a Waiwera holiday park and established their orchard on a former dairy run-off for their retirement.
A tractor or ute can tow the 1.5-tonne frost fan into position where four adjustable legs level and stabilise it. A cord is pulled to start a small Honda engine that powers hydraulics lifting a 7m boom on the end of which a 17kW V-twin Honda engine spins a 2m eight-blade impeller that oscillates, pushing out a stiff breeze circulating air for frost protection over up to 6ha.
The machine - inaudible at 300m - works a treat in the Nitschke orchard. It's won a couple of agricultural innovation awards and Mr McAuley said his staff were "flat out" building frost fans for export.
With frost under control, a small cicada-like insect - the tomato-potato psyllid - is now the main problem for the Whatitiri couple, and for tamarillo growers around the country.
Mr Nitschke, who is manager of the Tamarillo Growers' Association, said there had been about 120 orchards growing the South American fruit before the psyllid slipped through the biosecurity net from the United States.
The insect was discovered here in 2006.
A toxin it injects while feeding is devastating for tamarillos, reducing the number of orchards to about 35 by 2009.
"We had about 150 trees dying weekly. It was a scary time," Mr Nitschke said.
The association got Plant and Food Research to develop psyllid-slaying chemicals softer than environmentally dodgy organophosphates and the number of tamarillo growers is now back up to about 55.
"The pest is still killing about 5 per cent of trees annually, but we can live with that," Mr Nitschke said.
Returns for tamarillo growers topped $5 a kilogram when rampant psyllids trimmed production. However, with market supply now recovering, prices are back to the $3.50-$4 a kilogram pre-psyllid level.
That's a concern for growers, who believe they need a good price for the considerable effort they put into producing their fruit.
The Nitschkes grow two varieties of tamarillo - Laird's large and Mulligans - with each plant producing 5kg-10kg of fruit. Careful selection of breeding stock is developing fine fruit and they are eager for their industry to flourish.
But Mr Nitschke advised prospective growers to get expert advice before investing.