Growers question copper spray

Te Puke kiwifruit growers Russell Baker and Rob Bayly are concerned orchards being sprayed with copper formulations may be causing phytotoxic symptoms to appear on vines that can be mistakenly assumed to be secondary symptoms of Psa.
The orchardists recently commissioned NZ Horticultural Advisory Services to provide them with independent advice regarding Psa issues.
Senior adviser Alex Smith, M Hort Sc, has had experience in overcoming the effects of Pseudomonas syringae (PS) over 40 years. He recently inspected several Te Puke properties which had confirmed infections of Psa-V.
Among the issues Mr Smith addressed are the effects of copper spray on new growth.
Here's an extract from his report:
"It has come to our notice that KVH [Kiwifruit Vine Health] is recommending copper spraying at rates vastly in excess of those listed on labels for bacterial control of soft leaf growth.
"This practice is extremely dangerous. Some of the visible symptoms of copper toxicity are in many ways on most subjects identical to some of the symptoms of Pseudomonas syringae.
"Extensive tests by New Zealand Horticultural Advisory Service in many other organisations has shown that such applications of copper hydroxide, copper oxide and other related products can be extremely toxic to young immature leaf of many fruiting species in New Zealand.
"Wilting and associated leaf markings are expressions of the toxicity.
"Extensive testing over years has shown this to be true on kiwifruit, apples, peaches, nectarines, apricots, citrus and many others. Yet KVH continue to recommend this practice multiple times on the same property.
"Vine wilting typical of copper toxicity is now visible on many of these properties.
"We understand KVH staff are claiming that all of these cases are due to Psa and are recommending removal on the basis of field observations only.
"This is downright careless. It is further highly likely wrong. Errors have been made. Blocks have been cut down on the basis of visual observation only and the samples taken have turned out to be negative.
"The only conclusion to draw from this debacle is that the symptoms are not Psa and the blocks have been needlessly cut down in their prime.
"KVH is seriously wrong to be continuing to pressure growers into cutting down without confirmed authenticated peer reviewed results showing that a block is Psa-Virulent form positive."
Mr Baker says a lack of communication by KVH to growers in respect of this information and other issues such as the effects to vine health from cutting off in mid-summer has prompted him and Mr Bayley to set up a website www.psainfo.co.nz
It is their intention that this will serve as an open forum where affected growers and other interested parties can freely exchange information on Psa matters.
KVH was established following agreement of the Industry Advisory Council (IAC) to transition the management of the Psa response from MAF Biosecurity NZ and ZESPRI to a separate entity.
Their concerns have been teferred to KVH for comment:
Reply: KVH advises growers on the use of protective spray applications based on the best available knowledge and technical advice, gathered from the management of Psa overseas and in New Zealand.
Experiences in Italy have shown quick action is required to manage the spread of the disease, says Annette Scullion, KVH communication manager.
On-orchard investigations in Italy and laboratory tests conducted in New Zealand indicate the best products for protection against Psa infection are copper and the biological protectant Serenade Max.
KVH provides growers with guidelines and recommendations for spray use and detail the environmental conditions that contribute to optimum outcomes (eg avoid slow drying conditions).
Refer to www.kvh.org.nz for further information.
KVH acknowledges there have been incidences of foliar damage as a result of copper application, particularly where application has been outside recommended conditions.
It is KVH's opinion and therefore advice to orchardists that the protection offered by copper offsets any potential damage.
It is an individual's decision as to the risk/benefit analysis of potential foliar damage versus potential Psa infection.
KVH says copper spray is not the cause of the secondary symptoms observed on the orchards referenced, says Ms Scullion.
Zespri and KVH have been undertaking on-going field trials to better understand copper persistence and the amount of copper required to achieve Psa control (refer www.kvh.org.nz).
This information will be used to refine spray programmes going forward with an objective of reducing copper applications.
Zespri and KVH have also been trialing a range of products in the laboratory and the field that may become substitutes for copper.
Copper appears to be the best option for protection against Psa infection, she says.