Tauranga – New Zealand scientists and growers will be looking on with concern as kiwifruit vines in Italy are dying and no one really knows why.
The disease, dubbed moria (die off) or kiwifruit vine decline, causes the leaves to wither and fall and scientists are baffled. Within a year or two the plant dies.
The syndrome in Italy is now estimated to affect more than a quarter of orchards and 50 percent in the hardest hit area of Verona. It is costing the industry millions of Euros in losses.
Scientists suspect there are a number of factors at play, combining to cause the syndrome, but they are yet to identify the cause or, importantly, a cure.
Kiwifruit growers in Aotearoa know only too well the devastating impact a new disease or syndrome can have on the industry.
The leaves wither and face down as if to escape the sun; the roots darken and rot.
Then the leaves fall: within 10 days, all of them are gone, leaving the fruit under the sun. Within one or two years, the plant dries up and dies. There is no cure.
Italy is the world’s second-largest producer of the fruit – more than New Zealand and less than China which has almost 200,000 hectares in vines. Italy has 26,500ha, twice the size of New Zealand’s vines. Iran is the fourth biggest kiwifruit producer.
The kiwifruit industry is the biggest sector in New Zealand’s horticulture. Today, 2792 kiwifruit growers produce about 150 million trays for export from 12,905 productive hectares. In 2019/20 this was worth $2.967 billion in gross sales.
Meanwhile, Italian researchers say the real numbers of diseased vines could be even higher than estimated.
Because the syndrome starts in the roots, it can spread unobserved until the first leaf symptoms. By then, the decline is already too advanced.
Growers have seen similar leaf symptoms, sometimes attributed to drought, wind or Psa in New Zealand orchards.
The highly virulent bacterium Psa causes bacterial canker on kiwifruit vines and was first identified in New Zealand in 2010.
Marginally affected orchards can be managed by using Primazest / Agrizest for a short term solution, leading Kiwi environmental tech company Zest Biotech says.
The company’s chief technical officer Nathan Balasingham says in the long term, the industry needs to review the excessive use of fertilisers and foliar nutrients and adjust back to levels recommended for orchards, such as apples.
“The kiwifruit industry has been applying very high levels of nutrients for more than 25 years,” he says.