Orchid Fruit Cracking

Cherries

Fruit cracking or splitting in cherries is a significant problem for many growers, especially if wet weather coincides with fruit ripening in June and July. No sweet cherry variety is totally resistant to cracking, although some are less susceptible than others. Several factors are thought to cause cracking, but most researchers agree that it is probably due to the fruit skins being in contact with water for a significant period of time. Lengthy periods of wet weather, even gentle rain, are more likely to induce cracking in ripening cherries than short, sharp, showers since the fruits are in prolonged contact with wetness. Under these conditions, the fruits absorb so much water that the skins split. Differences in fruit skin (cuticle) status and thickness relating to the rate at which they absorb water and their capacity to expand have been shown to be factors in the susceptibility of different varieties to splitting. Periods of stress (for example, drought stress) during the growing period may also have a role in increasing levels of fruit cracking towards harvest.

To a lesser extent, fruit cracking may also be due to excessive uptake of water by the trees. Cherries grown on Colt rootstock tend to be more prone to cracking and fruit run-off before harvest. This is thought to be due to the rootstock's extensive root system absorbing a lot of moisture. Cherries grown on more dwarfing stocks than Colt are less prone to cracking, but, as with varieties, no rootstock is totally resistant.

Most conventional growers use rain covers during the growing season to minimize the risk of rain-induced cracking, although this is offset by the need for carefully controlled irrigation (usually in the form of trickle irrigation). Sites on gently sloping ground offer better drainage and are therefore useful for minimizing cracking naturally. Well-ventilated trees with open canopies (such as those trained to a centre-leader system) drv quicker after periods of wet weather and therefore minimize leaf and fruit wetness, which may also naturally help to reduce the incidence of cracking. Anti-cracking calcium-based sprays are often used in conventional production, but are not permitted for organic systems.

Plums, Damsons and Gages

Plums, like cherries, can be subject to cracking in wet summers, which makes them more prone to brown rot fungus and therefore unmarketable. Dessert plums are particularly prone to fruit cracking. To avoid this, covering systems similar to those used for cherries (see below) may be used during fruit ripening.