Apple and Peach Bud Development and How Late You Can Safely Apply Copper
Posted: April 5, 2011
Fortunately, the number is still way below threshold levels.
If you still need to apply copper on peach, it can be safely applied until the pink bud stage. Beyond that, the risk of plant damage increases.
For apples, any time after the 1/4 inch green stage is too late, especially on sensitive fresh market cultivars.