Care when applying copper sprays after fruit set
Psa leaf spots, and cankers which have been active through spring, continue to be potential Psa inoculum sources within the orchard. It is important growers consider their individual site risk and if risk is high, continue to apply copper at summer rates after fruit set. Ideally apply copper following canopy work such as male pruning rounds. Similarly, extra care with tool hygiene should be observed.
When applying coppers, for crop safety, maintain a five to seven-day gap between copper and foliar sprays, and do not apply sprays in poor drying conditions or high humidity. Check the pH of the spray mix and use buffers to adjust this as necessary. For example, Kocide Opti should not be applied at less than pH 6.5 as this may lead to fruit marking. Apply products on their own, rather than tank mixed with other products as this further reduces risk of leaf or fruit damage.
Take care with the timing of copper sprays applied after fruit set. The recommendation is to avoid spraying through skin sensitive periods. For Gold, skin sensitivity commences around 21 days after fruit set. The risk of fruit marking becomes higher between 28 and 42 days after fruit set, then risk lessens but still continues from 42 until 80 days after fruit set. For Hayward, 14 to 35 days after fruit set is considered a high-risk period. To avoid mistakes, note fruit set dates and safe spray periods on your calendar as an easy reference.