As the Psa-V toll continues to rise growers are preparing to use the controversial antibiotic spray KeyStrepto to help protect their vines.

Kiwifruit Vine Health says regulatory approval has been given for the off-label use of KeyStrepto, which was illegally injected into vines on some orchards last season resulting in a warning for growers from the Ministry of Primary Industries.

This season even more strict conditions are in place for its use as a pre-flowering Psa-protectant for kiwifruit growers in Psa-V-infected regions of New Zealand.

Those conditions include that it cannot be used for trunk injection or drip injection.

Further consideration will be given to making KeyStrepto available to growers outside of these regions on a case-by-case basis.

This week 55 new kiwifruit orchards were identified with the vine killing disease, meaning 1424 orchards are now infected.

In total 7220 ha, or 52 per cent of the area on which kiwifruit is grown in New Zealand now has the disease in some parts of the orchards.

Among the latest reported infections, six were in the Te Puke region; five in Waihi; one in Tauranga East; 12 in Tauranga West; 19 in Opotiki; and12 in Katikati.

Te Puke remains the most heavily infected area with 954 orchards with the disease, followed by Tauranga East with 143 orchards, Opotiki with 94, Whakatane with 77, Katikati with 65, Tauranga west with 43, Waihi with 33, Franklin with nine, Coromandel four, and Waikato two.
The only growing regions currently free of the disease are Poverty Bay/Hawkes Bay, Wanganui/Horowhenua and the South Island.

KVH says KeyStrepto will be made available subject to strict conditions of use including:

KVH must be notified 48 hours prior to application to allow auditing to ensure the orchard is suitable to be sprayed. Audits must be completed before application can commence.

The product must be applied at 60g /100L water.

Typical dilute spray volume required pre-flowering is 600 – 1000L water/ha for bearing or mature vines and should not exceed 1,200L water/ha.

The maximum amount of product per hectare permitted in one application is 720g/ha in a maximum of 1,200L water/ha; and the cumulative maximum that can be applied during the use period is 1.2kg/ha.

A maximum of two applications can be made on bearing or mature vines (over two years old), provided that, in total, not more than 1.2 kg product/ha is applied during the use period. Market access requirements for nil residues have been a key driver in developing the conditions of use for KeyStrepto.

A maximum of three applications can be made on developing non-bearing vines (under two- years-old), provided that, in total, not more than 1.2 kg product/ha is applied during the use period.

Non-bearing vines are vines that will not produce fruit within 12 months following treatment.

The product can only be used until one week before the first kiwifruit flowers (male or female) open in the orchard or until December 15, 2012, whichever comes first.

Low-drift technology must be used until the canopy develops.

KeyStrepto may only be applied as a foliar spray by ground-based application and no other methods of application are allowed, including injection.