When growers want to get an orchard of kiwifruit to fruit at the same time, they can spray a hydrogen cyanamide in August. The chemical, most commonly used in a spray called Hi-Cane, fakes the effect of a good winter frost for the vines, signalling it’s time for them to get flowers under way.
Fake frost means kiwifruit orchards can be planted in warmer places where fruiting may not happen - or at least not as uniformly or abundantly - without the chemical helper. It’s used from Northland to the Bay of Plenty and even in Nelson, where our southern-most orchards lie.
Hydrogen cyanamide products are currently up for reassessment by the Environmental Protection Authority (EPA). Depending on the outcome, there’s a chance the rules around its usage may change, or it could even be banned as it is in Europe.
In 2018, kiwifruit’s export revenue was $1.8 billion, representing 32 percent of New Zealand’s total horticultural export revenue.
NZ Kiwifruit Growers Inc CEO Nikki Johnson said the majority of New Zealand's almost 3000 orchards will be using the chemical. Its ability to compress the flowering season saves labour costs and ensures all fruit picked are uniformly ripe. Even in places with cooler winters like Nelson it’s used for this reason. Instead of having an orchard with fruit ripening over three or four weeks, you have ripe fruit all in the same week.
Removing the chemical from growers’ tool boxes could render many parts of the country unsuitable for growing the iconic export crop.
Research by NIWA published in 2017 mapped the country for where the green Hayward kiwifruit could be grown based on temperature with and without the use of the chemical. Climate change effects were thrown into the equation. Lead author Dr Andrew Tait said as air temperatures increased there was the likelihood of more mild winters. “This could put significant stress on the kiwifruit industry in the Te Puke area, particularly if hydrogen cyanamide is banned.”
While his research mainly focused on Te Puke, he did map the entire country. Without hydrogen cyanamide, much of the north has been ranked as ‘poor’ for growing since 1970 and becomes marginally worse by 2030 based on temperature.
There’s good reason to make a model such as this. The chemical helper has a catch. While it might be a convenient substance for kiwifruit growers, it’s not particularly nice. It’s toxic to humans, mammals, bees, aquatic organisms, and possibly birds.
The spray is banned in Europe for forcing flowering, but is approved as a ‘biocidal’ product. This means it can be used if the purpose is to kill something. It’s approved in Australia, the United States and Canada.