Autumn is a high risk period for Psa as cooler, wetter weather conditions favour multiplication and spread of disease.

The Psa-V risk model showed heightened Psa risk for most growing regions over the past week and looking forward risk continues to be moderate in areas such as the Waikato, Northland and parts of the Bay of Plenty (see image above - risk profile from the Karapiro weather station in the Waikato).

Growers should step up protection in line with these seasonal changes and individual orchard risk. For those harvesting later in the season applying a copper spray, when weather and ground conditions allow, will begin to rebuild protective cover across vines. A reminder that leaf spots can provide a source of inoculum so should be considered when making decisions on spray applications.

Immediately following harvest, growers should be getting copper spray programmes underway to help prevent Psa entering their vines through harvest wounds and leaf scars.

Incorporation of Actigard into a post-harvest programme will reduce the likelihood of disease symptoms appearing the following spring. Actigard can be tank mixed with copper and is most effective when applied to leaves that are still in good condition. Extreme care must be taken to avoid spray drift onto unharvested blocks. After spraying Actigard ensure that spray tanks, lines and nozzles are cleaned thoroughly before spraying other products on unharvested fruit.

For more information, refer to KVH's Psa-V Best Practice Guide.

Any growers concerned they may not be achieving the expected levels of Psa control from copper applications at label rates should contact KVH on 0800 665 825 or email info@kvh.org.nz.