Psa protection for harvested and development blocks important

02 May 2019

An observant Northland grower forwarded this image (right) to KVH from his new development block, showing Psa exudate developing on the underside of spotted Bruno leaves.

The block had developed some leaf spot symptoms in late spring, following a period of high winds and rain, but new leaders and laterals established throughout summer had remained clear of infection. This recent reactivation of Psa on the edge of leaf spots illustrates how Psa multiplication is favoured as temperatures drop through autumn, and an immediate application of winter rate copper was recommended to avoid infection spread.

Growers and outdoor nurseries are reminded to stay focused on protecting young rootstock and replacement plants through autumn as these are most vulnerable to Psa infection. Winter rate copper is recommended and additionally the biologicals Kiwivax (applied as a soil drench) and Botryzen are suited to autumn use. Refer to the KVH recommended product list.

Also apply copper to mature blocks immediately after harvest to protect fruit stalks and leaf scars. The Psa risk model currently predicts a good spray window available through to early next week for most regions.