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Spring Psa risk patterns

Spring Psa risk patterns

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27 Oct 21 Biosecurity News

Spring Psa risk patterns

Monthly Psa risk summaries reported from almost every weather station in the KVH network show Psa risk due to weather through September was the lowest recorded for this period in the last four years. This follows a trend of lower rainfall, with rain being a key driver of Psa risk.

In contrast, Wanganui and Levin stations reported September risk as high, matching the high-risk periods seen in the 2017/2018 season.

These trends match grower observations, with Wanganui reporting high levels of Psa symptoms from early in the season, while other regions have generally reported a quieter Psa year to date. Things can change quickly though, and growers should keep close watch on Risk Model forecasts. Currently most stations predict a lift to moderate risk within the next five days, and reports of leafspot from early Hayward blocks are a reminder that infection risk exists.

Growers with new development blocks are especially urged to keep a strong protective programme in place as young plants are vulnerable to Psa and recent chilling winds will have increased plant stress and caused microcracking in developing tissue. In more mature blocks, poorer bud break and wilting shoots on the ends of canes are indicators of Psa presence. Growers are urged to monitor their sites to help gauge the best control programme through to flowering. Ensure protection of wounds created through flower-bud thinning.

Hayward growers with high-risk sites should be planning pre-flower girdles. Correct timing is 30 days before flowering. Ambitious can also be incorporated into a Hayward protective programme.

A reminder, the Kasumin use window closes three weeks prior to flowering. Copper and Actigard may be used through the period leading up to flowering, and the Aureo Gold use period continues through until six weeks after flowering. Check the KVH seasonal management wall chart for product rates and use timings.


KVH investigates reports of unusual symptoms to identify and manage any biosecurity risks.

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