Copper use after flowering
Growers will be welcoming the blue skies and higher temperatures being seen across the country as typically Psa risk reduces significantly when temperatures rise to 20 degrees and above. A reminder though to keep watching the risk model, as pockets of moderate and high-risk weather can still occur. Image above is from the Opotiki weather station.
Psa leaf spots remain a potential inoculum source if weather favours Psa so it is important cover is applied following canopy work and male pruning rounds. Ensure protection is in place prior to high-risk weather.
When applying coppers, maintain a five to seven-day gap between applications of foliars and copper to minimise risk of phytotoxicity to leaves and fruit. Do not apply sprays in poor drying conditions, or high humidity, as risk of fruit staining increases.
Gold skin sensitivity commences around 21 days after fruit set with risk increasing between 28 and 42 days and reducing again between 42 and 80 days. For Hayward, 14 to 35 days after fruit set is considered a high-risk period. Copper may be applied during these periods but take care to ensure drying conditions are optimal.
Also choose low-risk weather periods when applying girdles. If copper sprays are used to cover girdling wounds, make sure correct rates are used. High rates of copper should not be applied directly to open girdles.