A further observation report on infected male vines shows how the effects of a colder site, Psa-V infection history, lower input Psa-V strategies (cultural management and protective spray programmes) and less-tolerant varieties can result in very compromised pollination potential.
Ongoing Psa-V management is necessary on all orchards and more challenging spring conditions clearly illustrate the re-emergence of Psa-V on vulnerable sites.
Monitoring and removal of infected material through spring remains a primary tool in reducing risk of Psa-V inoculum building and compromising orchard productivity.
Click here for the observation report.
KVH will hold its Annual General Meeting (AGM) at 2pm on Wednesday 26 November 2014 at Classic Flyers (Boeing Room), 9 Jean Batten Drive, Mount Maunganui—Google maps.
During bud-rot trials in Hayward and Green14 orchards last year, Actigard™ and copper spray programmes had the biggest impact in reducing Psa-V leaf spot. Applications of KeyStrepto™ also reduced leaf spot.
As Psa-V is associated with bud-rot, a protective programme that includes these products is highly recommended for all sites vulnerable to bud-rot. This will minimise leaf spot, which once established, can provide ongoing sources of inoculum.
Girdling provided the best bud-rot control. Recommended timing for girdling is 16-30 days pre-flowering. Further trials will run this year to better understand optimal girdle timing.
Growers intending to apply a pre-flower girdle should plan for this now. All growers are urged to measure impacts of this treatment on their site and share this information with the industry to build knowledge quickly about the value of this tool.
By leaving some control vines amongst girdled areas or alternatively, girdling only a few vines within high-risk blocks and measuring flower-to-fruit retention, assessment of the success of this tool across multiple sites can be gained. A methodology to assist growers has been developed by the Zespri OPC team – click here.
Exploring options for wound protection to prevent Psa-V infection of cut stems Bruno seedlings
Wound protection continues to be a challenge for kiwifruit growers since the incursion of a virulent strain of Pseudomonas syringae pv. actinidiae (Psa) in New Zealand in November 2010. When several products were tested in the field as wound protectants against natural infection by Psa, there were no significant differences between treatments (Miller et al. 2012). Therefore, there is demand in the kiwifruit sector for a wound protectant suitable for pruning wounds. This project evaluates a range of registered treatments not previously tested for protecting pruning wounds against Psa and explores the use of a penetrant for driving the product into the wound to provide protection in the case of bacteria entering the plant during the cutting process.
Click here for report by Plant & Food Research
The following presentations from Tuesday’s R&D grower meeting in Te Puke are now available on the KVH website:
Psa-V continues to spread throughout the Kerikeri region with 32 out of 106 KPINS now testing Psa-V positive. KVH staff recently visited positive orchards in Kerikeri with growers and orchard management staff.
In most cases disease expression has continued to be relatively slow. However, in one location inoculum levels have clearly increased and disease expression in Hort16A has increased significantly. This has led to a number of part blocks being removed. These orchards are carrying out weekly monitoring and removal of infected material, followed by weekly spraying.
Growers are advised to be aggressive with removal to help reduce the rate of spread and to protect young Gold3 grafts. The continued wet weather has clearly been a factor in disease spread, and unless the region sees a long period of warm, dry weather soon, growers can expect expression to continue to accelerate.
KVH recommends growers actively monitor their orchards, remove signs of infection and to contact packhouses or KVH staff for support if required.
In late 2013, Chile suffered one of its most damaging frost events in 80 years—causing almost $1 billion damage to fruit crops and reducing kiwifruit export volumes by over 50%.
Further impacts from this frost event are also expected in the form of Psa-V, with the number of positive orchards expected to increase when national surveys are carried out later this year. It is expected the colder areas near the mountains and further from the coast will be the most severely affected.
Over the past few years, Chile has seen a steady increase in the number of positive orchards as shown in the graph above.
Symptoms at newly-detected orchards are often severe, leading local authorities to believe these infections are not new, but have been undetected in previous monitoring rounds.
The Chilean Kiwifruit Committee states the industry needs a greater permanent awareness to biosecurity, and orchard management complacency is the biggest problem facing the Chilean industry.
Zespri’s Focus Orchard Network (FON) field days are scheduled from 7-21 October and include the following topics:
Click here to find the FON field day coming to your area
During spring, Psa-V symptoms can change quickly as sap rises. Therefore, ongoing monitoring of orchards is essential at this time of year.
Monitoring of male vines, particularly in areas where males were affected by Psa-V in previous years, is recommended to allow growers to make early assessments of likely artificial pollination needs. Pollen suppliers have indicated stocks are lower than in past years.
Following recent orchards visits, KVH has prepared the following observation reports:
Last month, ACVM granted a limited label claim to a second CPPU (forchlorofenuron) product – Caplit™ – for the control of Psa-V in kiwifruit.
Zespri has updated the CPPU User Guide and Crop Protection Standard to reflect this change; and KVH has included Caplit™ in its Recommended Product List.
The use conditions are the same for both Caplit™ and Ambitious® 10SL, so growers are prompted to add Caplit™ to their Seasonal Management Wall Chart alongside Ambitious® 10SL. Please note the rate for Caplit™ is 50-75g/100l.
Due to concerns around fruit deformation observed on Gold varieties off-shore, CPPU products should not be applied to Gold varieties.
CPPU products are not systemic and therefore good coverage is required. Apply approximately 5–7 days prior to an infection event. CPPU should not be applied within seven days of the first flowers opening on an orchard. Extreme care should be taken to mitigate the risk of spray drift.
KVH will present a Psa-V spring update at next week’s R&D grower meeting in Te Puke. This will include a national Psa-V update and infection management advice.
When: 3pm, Tuesday 30 September
Where: The Orchard Church, Te Puke
Last week, Grosafe Chemicals Ltd confirmed their copper Hydroxide product Hortcare® Copper Hydroxide 300 received BioGro certification, providing organic growers with another tool in the fight against Psa-V.
Zespri will include this change when they update the Crop Protection Standard.
As always, organic growers are reminded to confirm the BioGro status of all products prior to use, and ensure their ‘BioGro Organic Management Plan Inputs’ list remains updated.