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Waikato regional update
24 July 2015

In early July KVH revisited six Waikato orchards (both conventional and organic) to discuss harvest results and also understand how Psa-V had affected growers through the 2014-15 growing season.

Generally growers reported good harvests with excellent pollination and strong autumn growth, lifting fruit numbers, dry matter and fruit size.

On the Psa-V front, it was acknowledged that challenges are still very much front of mind, particularly on colder and less well-drained areas of orchards, or in areas highly exposed to wind. For some growers, river mists and hail events have added further challenges.

There are still a good number of Waikato blocks in recovery mode as Gold3 grafts develop and young plants replacing Chinensis rootstocks mature.

KVH revisited colder sites where organic Hayward males had severe Psa-V exudate symptoms last spring. Where males were cut back hard to remove infection, regrowth has been excellent. Further pruning rounds to encourage spur growth has resulted in great structure with spurs expected to be very floral for spring 2015. Grafting of older variety males to more Psa-V tolerant varieties continues as a strategy to further reduce site Psa-V risk. Infected female canes within the canopy were being removed during winter pruning.

One of the conventional Hayward sites visited similarly showed the impact of extensive spring infection of males. Previous management of the male vines had failed to focus on height and density reduction, resulting in vigorous and high growth becoming badly affected. An intense spring programme including elicitors, streptomycin and coppers had subsequently been followed. However, the impacts were still seen as many of the leaders remained ring-barked due to the severity of infection. Restructuring of the males was taking place.

KVH also revisited some young organic Gold3 blocks which had significant Psa-V cut-out last spring, sometimes with up to sixty percent of canopy removed.  Stringing had returned these blocks to almost full canopy. To protect this growth, autumn frost-fighting continued through May and early June 2015 as a strategy to reduce risk of frost damage to the young canes. It was thought that autumn frosts in the previous year had provided entry points for Psa-V, leading to spring infection. Observations next spring may help determine the value of this effort.

For the older Gold blocks, new canes continue to be tied in to replace trunks and leaders ring-barked by Psa-V infection (see photo); and where possible, cankered leaders and canes are being pruned out of the canopy as standard practice.

Overall, there appears to be increased use of copper for Psa-V management on organic orchards, with post-harvest and leaf-fall applications recognised as important to reduce the spread of Psa-V through the colder months. Applying copper as soon as possible after pruning is also being emphasised.

Citrox-BioAlexin is being applied across some organic blocks, again to determine whether Psa-V symptoms can be reduced through use of this product.  Organic growers trialling pre-flower girdles on Psa-V affected blocks reported that this practice had definitely reduced flower bud loss, with girdles applied a month out from flowering giving best results. This technique would be used again in 2015.

 

Kiwifruit Vine Health

25 Miro St
Mount Maunganui
Tauranga 3116

Tel:  0800 665 825
Fax: 07 574 7591

Email: info@kvh.org.nz