With the difficult spring weather conditions occurring in most regions, it is important growers take every opportunity to use a range of products within their spray programmes to minimise the risk of Psa infection and spread.
For those in high Psa risk situations, current weather patterns are likely to warrant application of a bactericide. These are best applied before infection is seen and timed prior to infection events such as extended wet weather, stormy periods, hail or frost. Applications within 48 hours after these events also provides control. Timing for Kasumin is when leaves reach 25mm in diameter, with use allowed used until 21 days prior to flowering. KeyStrepto, with JA, can be used up to seven days before the first flower opens.
Products such as Actigard and Ambitious should also be included for additional protection against leaf spot and flower bud infection. Most effective when applied before leafspot symptoms appear, optimal timings will vary with orchard location and variety.
First applications of Actigard can be made when leaves reach approximately 25mm in diameter. Delay applications if vines are under stress.
CPPU products, available for Green varieties only, need 5-7 days to raise a response and should be applied when there is sufficient leaf for absorption. As a guide, shoots should be around 100mm long.
Coppers at full summer rates remain the backbone of the spray programme and need to be reapplied to match the rate of shoot extension.
Pre-flower girdles for Green blocks at high risk of flower bud infection should also be planned. These need to be applied in dry conditions, around 30 days before flowering.
Use the Psa-V Risk model
to assess upcoming risk for timing of spray applications.