Questions and Answers
What is streptomycin?
Streptomycin is an antibacterial product and has been registered for use against Psa-V in New Zealand since 2011.
Antibacterial products are registered for use in Canada, United States, New Zealand and a number of Asian countries against a range of bacterial diseases in horticulture, including fire blight in apples and pears.
It is registered in New Zealand for use on apples, tomatoes, stonefruit and kiwifruit.
Why is it used in the NZ kiwifruit industry?
MPI granted a Limited Label Claim with strict use conditions for streptomycin for the control of Psa-V on kiwifruit vines.
Antibacterials are considered to be one of the most effective tools for managing Psa-V infection. For information on efficacy refer to: www.kvh.org.nz/product_testing_results.
How has resistance developed?
We are still investigating the exact nature of the resistance but this can occur naturally as a result of other bacteria “sharing” their DNA.
Bacteria can also sometimes change genetically to resist protective products, meaning they are no longer effective against Psa-V. For more information refer to Plant & Food Research scientist Joel Vaneste’s technical presentation on KeyStrepto™ use and resistance on YouTube (link here).
Overseas experience has seen resistance develop in Pseudomonas sp. against both copper and antibacterials. Ceasing use of the product for a period of time is the key way of overcoming resistance.
Why did the NZ kiwifruit industry introduce streptomycin to the CPS if resistance has developed with its use in other industries?
When Psa-V was discovered in NZ, antibacterials were considered a necessary tool to help control Psa-V and allow commercial production to continue. Advice was provided to growers to limit the development of resistance through alternating protectant products, using recommended label rates, ensuring good spray coverage and maintaining orchard hygiene and removing infected material from orchards.
Will KeyStrepto™ be removed from the Zespri CPS?
KVH and Zespri are reviewing the ongoing kiwifruit industry use conditions of KeyStrepto™ in the Zespri Crop Protection Standard and industry will be advised once confirmed. We expect this decision to be made in June.
Is there another antibacterial growers could use instead?
Zespri is also reviewing the data on another antibacterial product Kasumin (active ingredient kasugamycin) to determine if it will be included in the 2016 Crop Protection Standard. This decision will be communicated to industry in June as well.
Can growers still use streptomycin?
Industry use of streptomycin is currently prohibited under Zespri’s Crop Protection Standard until its use conditions have been confirmed.
Zespri does not allow applications of KeyStrepto to fruit and has a zero-antibiotic residue policy underpinned by a 100 percent residue-testing programme of all orchards for antibacterial residues. All orchards are also subject to a multi-residue test, which tests for 300 active compounds. In the four years this testing programme has been in place, no antibacterial residues have been detected in crops.
What commitment is there to finding sustainable ways to manage Psa-V?
To date, more than $12m has been spent on a global research and development programme for Psa-V since it was detected in 2010; and a further $2m per year is committed to R&D into the future.
The R&D programme includes a product testing programme developed to identify, rigorously test and get permission to use suitable products to help manage and control the spread of Psa-V. To date, more than 300 products have been tested for efficacy against Psa-V in the KVH/Zespri product testing programme.