Weather patterns bring Psa risk to the north
June rainfall was above normal (120-149% of normal) or well above normal (>149% of normal) for parts of Northland, Auckland, Bay of Plenty, Gisborne, and Hawke’s Bay this year, bringing welcome relief after some very long, dry periods. For Northland, this high rainfall pattern has continued through July and August, challenging growers in terms of winter pruning and also application of protective winter coppers.
The Maungatapere (Whangarei) weather station shows that more than 50% of days from 1 June were reported as posing severe risk for Psa infection and spread (red bars in the graph below). Within this timeframe there were at least two periods where rain and associated severe Psa risk continued for more than a week.
Growers in the Whangarei region are strongly recommended to take every opportunity to rebuild protective copper cover across their vines to provide protection from Psa as we move towards budbreak.
As sap flow begins this month, all growers are also urged to monitor vines closely for Psa symptoms. On sites where Psa has already been detected, be proactive in cutting out infected material found and remove this from the orchard to avoid further Psa spread. Tool hygiene remains important on all sites, and growers should be sure that all staff are familiar with orchard hygiene rules. Psa symptom guides are available from KVH to assist with training of monitor staff. Active monitoring will provide the best chance that any further spread of Psa in the region is found early.
Growers concerned that they are seeing Psa symptoms for the first time can contact KVH on 0800 665 825 or KVH Regional Coordinator Pauline Kell for support in sampling and testing of symptomatic vines.
Higher seasonal Psa risk is also being reported for other regions. Growers can check the Psa Risk Model and use this tool to guide spray decisions leading up to the very high-risk spring period.