We all know how oppressive the mid-June rains were for many of us in Ohio, but how do you think the sweet cherries felt? It turns out that excessive moisture is a significant problem for this stone fruit. Fruit cracking from moisture can occur from several causes, from prolonged exposure to too much water in the root zone, but perhaps most likely from continued rainwater on the developing fruits.
In areas of northeast Ohio rain and relatively cool temperatures prevailed seemingly every day for weeks recently, including six inches or more in two days. This resulted in continuous water on those fruits with their thin cuticles as the fruit started the early period of ripening. Microcracks in the fruit at this point can expand from water absorption. Periods of rainfall in excess of 1.5 inches are known to enhance such cracking.
What can prevent this? In high production areas, intensive management is usually the only way to limit this problem if heavy rains keep coming. This includes drying the fruits in an orchard with airblast sprayers or even helicopters, the use of retractable orchard covers, and use of spraying hydrophobic coatings or osmotic salts multiple times. So, nothing for the faint of heart or pocketbook. To some extent, this has resulted in increasing sweet cherry production in drier climes. Otherwise, no-rain dances, though this has proved ineffective this year.
There are of course other hazards of horticulture for cherry production. Birds can strip the fruit. And Monilinia brown rot may follow cracking, moisture accumulation, and bird damage. The common brown rot disease, caused by the Monilinia fructicola fungus, occurs on stone fruits such as cherry, peach, apricot, plum, and almond (elsewhere) in the genus Prunus¸ with blossom and twig infections leading to fruit rots that result in un-harvestable fruit mummies. Moisture and injury to plant tissue favors disease development. Fungicides and sanitation (rogueing out affected fruit) are control practices.
Here are two excellent references for cherry fruit cracking that were used in compiling this bygl-alert: