The second wave of the vine-killing disease Psa-V is sweeping through Bay of Plenty kiwifruit orchards with spring testing showing higher-than-expected rates of infection in the main variety of green kiwifruit.
Until now Psa infection has mostly affected a gold kiwifruit variety known as Hort16A but recent testing and anecdotal evidence suggests male Hayward vines are succumbing to the disease in greater numbers than previously expected.
The bad news comes as kiwifruit growers prepare to pollinate their orchards and are faced with reduced numbers of flowers due to the necessity of cutting infected vines.
If flower numbers are severely reduced, growers will be unable to achieve optimal pollination which would have a flow-on effect on the amount of fruit harvested next year, Kiwifruit Vine Health (KVH) technical manager Linda Peacock said.
"Inadequate pollen supply and poor pollination results in small or misshapen fruit. This severely reduces the value of the resultant crop and may result in businesses becoming unprofitable," Ms Peacock said.
Te Puke kiwifruit grower John Cook said he was probably going to have to cut out 40 per cent of his male vines as a result of Psa infection.
"It means that we're going to struggle for natural pollination, so it's going to need supplementary pollen supply and I'm a bit fearful of the cost of that," he said.
The cost of artificial pollen would likely be inflated by an increased demand and a reduced supply, Ms Peacock said.
"There will be a higher demand for artificial pollen this season.
"The supply of pollen is likely to be restricted because foreign imports are not allowed. Also, pollen companies in Psa affected areas did not collect pollen last year as the ability of pollen to be a vector in disease transfer was not well understood and was considered a potential risk," she said.
With restrictions on moving pollen between regions, some areas may end up with an undersupply of pollen.
"This may mean some orchards are not able to pollinate their vines this year," Ms Peacock said.
Mr Cook said the situation was concerning for growers because they were unsure how much pollen they would be able to acquire and as a result how much fruit they would be able to grow.
"The ones who read the signals early got in early and protected their supply," Mr Cook said.
New Zealand Kiwifruit Growers Inc chairman Neil Trebilco said it was difficult to know how much the spread of Psa into the Hayward male vines would affect growers.
"We won't know until we've been through flowering and that happens in November," Mr Trebilco said.
"Some orchards will be fine and some orchards will have more impact."
A Zespri spokesperson said it was too early to know how next year's crop might be affected by Psa infection in the Hayward variety, but gold kiwifruit numbers were expected to be down.
Zespri expected to have a clearer picture of the Hayward situation by the end of the year.
"However early indications are that flower numbers on green orchards are high, following a cold winter. While we've seen some green vines removed due to Psa, this has primarily been males and we're anticipating a limited impact on the 2013 crop."
Ms Peacock said a pro-active Psa management plan was essential for all kiwifruit growers.
"KVH's Seasonal Management Guide is available for growers and the industry to provide recommendations and best-practice advice to help manage kiwifruit orchards in a Psa-V environment.
"A best practice male management document has also recently been provided to all growers and is available on the KVH website," she said.By Joseph Aldridge of the Bay of Plenty Times