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Early signs of Psa reported

Early signs of Psa reported

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04 Aug 22 Biosecurity News

Early signs of Psa reported

Last week KVH received reports of Psa exudate from a young Red19 block in Kerikeri and an Edgecumbe Gold3 site where exudate was associated with plants that had deep unhealed girdles.

These early signs indicate sap is rising and provides a heads up for growers that there is value in monitoring their high-risk Psa areas for early symptoms.

Winter Psa infection risk was generally higher this year in comparison with previous seasons for many areas, due to the ongoing wet periods across the last two months. In particular, the Psa Risk Model seasonal risk calculators show that for Te Puke, Whakatane, and Te Teko areas Psa weather risk through June was around 40% higher than levels seen in the previous four years.

This coupled with the challenge of fine days for pruning and limited clear days for follow-up spray means canopies with cankers overwintering in rootstocks or woody tissue will likely run the risk of seeing spread within the canopy and potentially higher inoculum loads this spring.

Growers can plan to rebuild strong copper cover ahead of budbreak, considering the need to allow one week between applications of budbreak enhancers and copper. Research has shown that protection in this period is key to managing Psa inoculum and reducing risk of leaf and flower bud infection.

The average timing of Red19 budbreak and flowering is up to three weeks ahead of Gold3, so Red19 growers are reminded that this means early Psa protection should be planned for now. We also know that Gold3 on Bounty rootstock breaks bud ahead of Gold3 on Bruno and the Gold3-Bounty combination is more susceptible to flower bud infection so good forward planning is needed.

Refer to the Spotlight on Psa for advice on how to get the best from your Psa management plan.


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

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