Psa symptoms and management

We’re aware that since the last week of October, and just before Labour Weekend, many growers may have noticed or heard from others that Psa symptoms have appeared on several sites.

We’re interested in feedback regarding your orchard/s so please do get in touch if you have any questions or concerns after having a read of the summary we’ve put together below of what has been reported lately.

The season so far

2021 spring weather patterns have heavily favoured Psa, much more so than in recent years.

Since bud break, we have had long periods (days) of leaf wetness weekly, plus cold winds. These conditions have both favoured Psa, and reduced opportunities for growers to apply protective sprays.

Patchy bud break on some sites has meant more gaps in the kiwifruit canopy, leaving vines exposed to wind which increases plant stress and vulnerability to Psa. Psa is known to enter plants through natural wounds such as micro-cracking caused by wind and frosts.

Bays, rows and orchards exposed to the prevailing weather, typically from the north-east this year, are generally worst affected. Sometimes quite distinct lines separate affected/non-affected areas, with these relating back to shelter protection. Covered blocks have fewer symptoms, although some growers suggest leaf spotting is slightly higher than previous years and with some infection found at the ends of canes. This could possibly link to infection occurring through the winter pruning period.

Even some sites with strong Psa management and spray programmes are seeing effects, with the general theme of shelter showing up as the trump card in Psa management this year.

We’ve received numerous reports and have photos of typical symptoms seen lately – view some of the images here and some short video footage here.

Going forward

Last weekend, and for some of this week, there were breaks in the weather which has allowed protective sprays to be applied, and on many Gold sites the bees are already in and have been active so pollination should be going well. Aureo Gold is available to help dampen inoculum loads for blocks through pollination if needed. It is also important that going forward, growers take out infection/collapsed vines to remove ongoing inoculum sources (at least before autumn when infection risk rises).

For Hayward blocks, flowering is two to three weeks away, and focus should be on inoculum management to minimise flower bud infection. Actigard and summer rate copper are recommended to provide forward protection, and for badly affected sites, including the East Coast and Opotiki orchards recently affected by damaging winds, growers may apply for a JA to apply Keystrepto, by contacting [email protected].

Keystrepto user guide rules must be met and growers need to be sure applications pose no risk to adjacent Gold or Red blocks. Aureo Gold is also available for both conventional and organic growers, with a reminder that this product should not be applied closer than 10 days after Kocide or 14 days after Nordox and should not be tank mixed with coppers.

The Psa Risk Model show that unsettled weather continues for most regions over the next 10 days with mid next week currently the best opportunity to get sprays applied. If you do not already have a login for the model you can register via the KVH website here.

Management advice and support

There are several types of resources available to assist growers with Psa advice, including:

• Most recently – on Tuesday morning – we recorded a podcast with Mike Montgomery on his orchard in Paengaroa and he talked about managing Psa on Bounty rootstock and the symptoms he has seen recently. Mike also discussed the support and advice he has received and how important this has been for him and his team. We’ve had great feedback so far so do have a listen here.
  
  
• Our Psa Best Practice Guide provides year-round guidance for protecting and managing your orchard in a Psa environment. It includes advice based on scientific research and on-orchard experience.
  
  
• There is also a seasonal wall chart poster available that details cultural methods and spray planning as part of building a Psa plan that matches your orchard. We have A3 sized copies printed that can be mailed to you – please provide a postal address to the office.
  
  
• A series of online Psa resources have been created to support growers, managers and post-harvest gain a greater understanding of Psa management activities on-orchard and share practical knowledge with their teams. Including both video and print, these resources are easy-to-follow and thought provoking when used to develop Psa disease management programmes.
  
  
• We recently produced a Spotlight on Psa for the Kiwiflier, alongside Zespri. This is available online and graphically provides an understanding of the Psa disease cycle and maximising your Psa programme's potential.
  
  
• An easy read reminder on the value of the Psa Risk Model to predict forward risk is also available on the Farmlands website from their Growing Success magazine. A reminder that if you do not already have a login for the model you can register via the KVH website here.
  
  
• The Biosecurity Innovation Portfolio also continues to invest in Psa research projects to help growers in the management of Psa. There is currently a two-year project underway testing the relative efficacy of a range of spray programmes, and we look forward to sharing learnings from this project with growers in the future.

KVH recommends you work with your pack-house to decide strategies to manage Psa-V on your orchard, or contact us directly with any specific questions. Technical support from Farmlands, and PGG Wrightsons - Fruitfed teams can also provide excellent advice on Psa product choice and strategies to rebuild wind damaged canopies.

If you suspect Psa in your orchard for the first time, make a report to us at KVH within 48 hours so that sampling and testing can be arranged, and support can be provided.