A jump in the number of registrations of hormone sprays containing the same synthetic chemical that helped make watermelons explode like landmines in China is puzzling Kiwifruit exporter Zespri.
The sprays, which contain a synthetic cytokinine, forchlorfenuron, have been shown to increase average kiwifruit weights by up to 46 per cent.
Chinese
state broadcaster CCTV reported farmers sprayed their fruit late in the season and during wet conditions, causing the melons to explode like "landmines".
The chemical has been registered in New Zealand since 1993, under the trade name Caplit, as a "plant growth regulator for sizing kiwifruit".
Field trials carried out at Goldwood Orchard near Waihi in the Western Bay of Plenty showed that forchlorfenuron sprays could boost the average fruit weight by 27 per cent to 46 per cent without affecting the proportion of fruit rejected for export.
But the United States' Environmental Protection Agency (EPA) - which said tests showed the chemical damaged rat kidneys - announced in 2001 it would ban the import of fruit with forchlorfenuron residues.
A Zespri spokesman said the policy on Caplit remained the same.
"Any grower found to have been using it will not have their fruit accepted for export by Zespri," he said. "Kiwifruit growers are well aware of the fact they cannot use it."
There was random testing of fruit from up to a quarter of all orchards that submitted fruit.
But the spokesman said he could not explain why in recent years there had been a jump in the number of products being registered for enhancing kiwifruit size: agricultural chemical company Cropstar registered powder and liquid formulations of forchlorfenuron in 2008 as a "plant growth regulator for sizing kiwifruit", and manufacturer Agrinova NZ Ltd registered Ambitious in 2009 as a "plant growth regulator for sizing kiwifruit and apples".
Agrinova said in its application to have the chemical registered that it could boost kiwifruit size by 20 per cent, but when extra-large fruit were needed for special markets, it should be used at a higher concentration. It also suggested also spraying small apple cultivars such as jazz and royal gala to boost fruit size.
However, a company spokesman said Zespri did not allow its growers to use the hormone.
Agrinova had not yet sold the product for use on apples, though it had just gained the registration for that, after five years of development work, he said.
