Key Industries, the New Zealand supplier of KeyStrepto™ have advised there is currently no stock of KeyStrepto™ available for kiwifruit growers due to demand far exceeding supply. Zespri, KVH and retailers have been working with Key Industries to secure more supply as soon as possible. The shortage is due to offshore production constraints, not transportation.
As a result, it appears unlikely sufficient KeyStrepto™ supplies will be available to the kiwifruit industry before flowering this season.
Growers should re-consider their Psa-V control plan and ensure alternative control products are used.
Alternative Psa-V control products allowed pre-flowering include:
Growers should not consider using Kasumin® as a replacement for KeyStrepto™. Kasumin® has been removed from the Zespri Crop Protection Programme for the 2015 season while further research is done to confirm the most effective use pattern. This work is expected to confirm the optimal pre-flowering withholding period for Kasumin® and the number of applications allowed in the pre-flowering period.
Symptoms of female flower bud infection are being seen on some Hayward orchards which suffered bud-rot in previous years. Brown discolouration of sepals and fine droplets of moisture on the surface of the buds are likely indications of Psa-V presence. These symptoms may not necessarily have obvious leaf spot associated with them. Within the same blocks, presence of red exudate on terminal buds, collapsed shoots and infected buds on the ends of female canes are other signs of Psa-V.
Growers are recommended to preferentially remove infected buds in pre-flower thinning rounds, cut back infected canes, continue with a protective spray programme and consider a pre-flowering girdle to help with bud-rot control.
Recommended timing for a pre-flower girdling for bud-rot control is 16-30 days pre-flowering so growers should plan for this now.
All growers are urged to measure impacts of this treatment on their site. Leave some control vines amongst girdled areas or alternatively, girdle only a few vines within high-risk blocks and measure flower-to-fruit retention for treated and control vines. A methodology to assist growers has been developed by the Zespri OPC team.
Tool hygiene is essential when pruning and/or girdling within these blocks.
Last week KVH followed up on two reports of unpruned orchards within the Te Puke region. Removal of vines was nearing completion on one property and the lease status of the second is being followed up.
Rules within the NPMP require completion of winter pruning (cutting and tying down of vines) by 1 October each year. Growers or concerned parties should contact KVH for follow-up of suspected unpruned or unmanaged blocks. NPMP rules are in place to reduce the risk of blocks harbouring Psa-V and providing risk to neighbouring orchards.
Growers should monitor their male vines for Psa-V infection and work to remove or reduce cankers where they occur. Cankers are Psa-V inoculum sources and create infection risk for male and female flower-buds. Infected male flowers can result in insufficient male pollen supply within the orchard and severely impact on orchard productivity. Where male plants are showing infection, assess pollen needs and make arrangements with your pollen provider now. Indications are that pollen availability is low this season.
Growers and those with stored pollen available for sale are reminded the movement of pollen between orchards and regions must be managed to minimise the risk of Psa-V spread.
Key requirements for providing pollen:
In a recent in-vitro study wound protectant Prunetec demonstrated absolute kill of Psa-V within an hour of incubation. Minimum inhibitory concentration, kill rate versus time and repeatability were tested by Verified Lab Services (VLS). VLS has previously conducted in vitro testing of other wound protectants commonly used in the industry.
Prunetec is listed in the Zespri Crop Protection Standard and is suitable for covering pruning wounds and for use when grafting.
In early October, KVH staff completed a round of monitoring on six Whangarei orchards to confirm the region’s ‘Exclusion’ status.
The orchards were chosen to represent the region with the focus on Hort16A plantings due to their higher susceptibility to Psa-V.
Samples taken from two CK3 males showing Psa-V like symptoms on one orchard were tested and confirmed ‘Not Detected’. There were no other visible signs of Psa-V symptoms on the other orchards.
A review of the 2014 season spray diaries showed four of the six orchards had good protective spray programmes in place and all orchards had good hygiene protocols in place. The growers had plans to convert their Hort16A blocks to less susceptible varieties; and some had begun this process by stump or notch grafting some of their Hort16A blocks to Gold3.
Due to Whangarei’s close proximity to Kerikeri (a containment region where Psa-V has spread this season) it’s essential Whangarei growers remain proactive with their protective spray programmes and hygiene practices to continue to keep Psa-V out of their region.
A report of the Whangarei monitoring will be available on the KVH website shortly.
France is one of the largest kiwifruit production countries in Europe, and like most kiwifruit production regions is infected with the global outbreak strain of Psa-V (r Biovar 3).
As at autumn 2013, France had about 4400 hectares planted in the following cultivars:
Estimates of total Psa-V infection rates are difficult to obtain. The French Ministry of Agriculture provides official data at the annual Psa meeting each February for the previous year. Therefore, 2013 data is the latest official data available.
In 2013, 2344 hectares of kiwifruit were officially inspected for Psa with 123 samples returning positive results (out of 400 taken from orchards with symptoms). This represents 386 canopy hectares or 8.9 percent of the total industry.
However reports based on visual inspections since 2011 suggest the cumulated infection rate is much higher—around 50 percent. Since 2011, four percent of the orchards have been cut back or removed.
Data from 2014 survey will be released in February 2015 and KVH will report these when they become available.
MPI have established a working group to improve and clarify the requirements for managing the risk of fruit fly entering through the commercial fresh produce pathway.
Although the commercial produce pathway is considered to be well managed and relatively low risk, MPI has identified several pieces of work necessary to maintain a high level of biosecurity risk management.
The group will review work being undertaken and communicate progress back to respective industries on an on-going basis. KVH is participating in this group along with representatives from other New Zealand horticultural industries.