Eye on the Psa Risk Model

18 March 2021

The Psa Risk Model currently predicts moderate Psa infection risk through next week for Kerikeri, Maungatapere, and Gisborne.

This is a reminder that risk of Psa rises as we move into the autumn period, with weather conditions again suited to the development of infection via inoculum associated with previous infections, including leaf spots and cankers.

Growers with early harvest blocks should apply copper to protect fruit stalks and soft tissue within the canopy. Apply this alone if there is any risk of drift and then plan to follow up with an Actigard spray when neighbouring blocks have been harvested.

Be cautious in applying Actigard to vines that have been severely stressed by drought – it is not recommended for vines showing signs of stress such as wilting, premature leaf yellowing or leaf drop.

Be sure sprayers are well rinsed to avoid contamination of following tank mixes.

Young plants also benefit from protective coppers to avoid infection risk to late grown tissue, and especially for blocks with significant leaf spot as Psa can reactivate from the edges of these spots once conditions become cooler and wetter.