Management of Psa-V post-harvest with Actigard

The use of Actigard is recommended as soon as possible after harvest, as this helps protect kiwifruit vines during the autumn high-risk period for Psa-V infection.

Research has shown a well-timed application of Actigard in autumn can help to reduce infection symptoms the following spring.

The cooler and wetter weather in autumn provides conditions conducive to Psa-V infection in kiwifruit orchards. Vines are vulnerable to infection, with around 300,000 to 500,000 fruit stalk wounds per hectare created by the harvesting of the season’s crop.

Late season growth (particularly in male vines) is also vulnerable to Psa-V infection, as are wounds caused by high winds and frost.

One of the key recommendations for post-harvest use of Actigard is to apply the product onto vines while the leaves are still green and actively photosynthesising. This allows the product to be sufficiently absorbed in order to activate the plant.

Actigard is likely to be less effective when applied to leaves at an advanced stage of deterioration, i.e. mid to late leaf-fall, or after a significant frost event.

As leaf-fall progresses, tens of thousands of potential infection entry points are created, which can render vines even more susceptible to infection during high risk weather events.

As it can take up to 7 days for Actigard to become effective, it’s important to apply Actigard prior to high risk weather events with the addition of copper for immediate protection.

Recommendations for post-harvest applications of Actigard

• Apply 200 g/ha of Actigard plus copper immediately post-harvest as a foliar spray to protect fruit stalks and leaves.
• Ensure thorough coverage of the canopy and fruit stalks.
• If canopy condition allows (i.e. leaves are still green) and infection risk remains high, reapply Actigard 4 weeks later to extend protection into the leaf-fall period (assuming you have not exceeded the maximum of 4 Actigard applications per year).
• To avoid the risk of residues when spraying Actigard post-harvest, take extreme care to avoid spray drift into unharvested areas of the orchard.
• Spray tanks, lines and nozzles must be cleaned thoroughly before any applications onto unharvested vines.
• As it can take up to 7 days for Actigard to fully activate the plant’s Systemic Acquired Resistance (SAR) response, the addition of copper is recommended for immediate protection prior to weather events.
• If vines are under stress, delay the application of Actigard until they have recovered.
• Actigard can be applied up to 4 times per year at 21 day intervals (pre-flowering and post-harvest).

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