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Protecting orchards from Psa through autumn
5 April 2018

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

The Psa Risk Model shows heightened Psa risk from early next week for most growing regions, with moderate risk indicated for the Waikato areas – see the Karapiro weather station image below. This change in risk is normal as night temperatures begin to drop and autumn rain fronts move across the country.



Growers should step up protection in line with these seasonal changes and individual orchard risk. Ensure young replacement plants and development blocks are protected with summer rate copper as young plants are more vulnerable to Psa infection. Also apply copper to protect strung canes brought down through autumn to ensure wounds are covered before high-risk weather occurs.  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 Best Practice Guide and the latest Actigard technote.

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.

Kiwifruit Vine Health

Suite 3, Level 1, Customhouse Building
314 Maunganui Road, Mount Maunganui
(entrance cnr Totara and Rata Street)
PO Box 4246, Mount Maunganui, 3149
New Zealand

Tel:  0800 665 825
Fax: 07 574 7591

Email: info@kvh.org.nz