Protecting orchards after harvest

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.

Following the discovery of copper-tolerant and streptomycin-resistant Psa developing on some orchards, a robust spray programme and cutting out infected material is particulary important through autumn and winter to reduce the spread of these new Psa strains.

Best practice advice for post-harvest protection and managing tolerance and resistance:

• Starting after harvest, maintain a comprehensive copper programme through autum and winter including a minimum of five copper applications at full winter rates.
• Ensure water rates are sufficient for complete canopy coverage. The addition of spreaders will improve coverage.
• As autumn progresses, maintain copper cover to protect fresh leaf scars. This is particularly important following the use of leaf drop sprays.
• Carry out good tool hygiene between vines during winter pruning and remove infected material from orchards.
• Apply coppers prior and post winter pruning.

Autumn and winter are high-risk periods for Psa-V. While vines are dormant the disease can still be active and enter through pruning wounds, new grafts and frost-damaged tissue.

For more information, refer to KVH’s Psa-V Best Practice Guide at www.kvh.org.nz/seasonal_advice.

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 [email protected].