Spring weather Psa protection

Wet spring conditions are ideal for Psa build up and infection of young tender growth. Over the last week and a half KVH has been at orchards and Zespri OPC spring field days seeing and recording symptoms – view a Psa photo gallery on the KVH website.

With the KVH Risk Model showing days of wet weather, this is a timely reminder that growers must maintain full spray cover over the season, particularly prior to, or directly after high-risk weather, on all varieties. Those with young plants and grafts (which are particularly vulnerable) need to take care that they are getting strong protection on, and have good coverage.

The online KVH Psa Risk Model can help with this and should be used to plan spray timings. The model is a weather-based tool that uses actual weather station data and weather forecast information to provide customised access to weather and disease interpretations.

There are several spray product options available. Be sure to meet all user guide requirements. If applying bactericides ensure there are no flowers present in the sward or on vines. KVH has produced a fact sheet covering spray products - including copper, bactericides (Kasumin), Actigard and CPPU for green varieties - and recommended timings for each. CPPU products may only be applied to Green varieties and may not be painted directly onto vines as this practice is not approved by ACVM.

Key points on the use of preflower girdles are also included in the fact sheet, including:

• For green varieties (Hayward and Gold14) in high Psa risk areas apply a full trunk girdle 30 days before the first female flower opens. This will reduce sepal staining and Psa budrot, therefore improving fruit-set.
• Only girdle in fine weather, check girdle depth, and sanitise tools between every vine.
• Girdle older trunks rather than young scions.
• Avoid girdling stressed vines.

Copies of the factsheet are available on the KVH website.