Effects of copper-calcium sprays on fruit cracking in sweet cherry (Prunus avium)

An effective and potentially commercial reduction of cracking in sweet cherries is reported from experiments conducted on five sites over three seasons. The treatment, Cu(OH)2 at 200 g per 1001 plus Ca(OH)2 at 3 kg per 1001 applied at 3 and 6 weeks after full bloom, resulted in a significant and consistent reduction in the proportion of cracked fruit from susceptible cultivars after moderate crack-inducing rainfall. On the three sites where rain-induced cracking occurred, calcium hydroxide was ineffective but copper hydroxide alone, at a low concentration or in combination with calcium hydroxide, significantly reduced fruit cracking. On the remaining two sites cracking of immersed fruit confirmed the field results. The increase in number of intact fruit for the copper hydroxide-calcium hydroxide mixture ranged from 27 to 36% in trials where rain-induced fruit cracking occurred. The treatments were ineffective in controlling cracking during an extended rain period of 12 days. © 1995.