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Rain induced fruit cracking in sweet cherries takes 3 distinct forms: stem end cuticular fractures, calyx end cuticular fractures, and large cracks usually deep into the pulp on the cheek of the fruit. A 4-year study of sweet cherry varieties from a commercial orchard in Tasmania, Australia, was conducted to investigate the incidence of crack type and its relative likelihood, as influenced by both genotype and season. Although all 3 crack types developed in the 3-week period before commercial harvest, the extent of cracking was strongly controlled by season. While initial development of cracks coincided with rainfall, no relationship between amount of rain and incidence of cracking was found for crack type. A significant relationship was found between the tangential stress experienced by fruit skin from fruit at harvest maturity and the incidence of cracking recorded in the orchard. No other fruit property (pulp osmotic potential, fruit diameter, weight) explained the differences in incidence of cracking in the field between seasons or varieties. The results suggest that management of cracking needs to consider both varietal and seasonal factors. The development of turgor in maturing fruit also needs further investigation.

Balanced crop load is key to the production of export-quality cherries. We investigated the level and timing of crop load regulation on fruit quality. Additionally we sought to investigate possible correlation between firmness estimated by compression test or flesh penetrability. Fruit diameter was similar between 1 and 2 bud/spur treatments but was significantly lower in the 4 bud/spur treatment at all thinning times in 'Van' in the 2010/11 season. In contrast 'Sweetheart' fruit diameter was only decreased at 6 and 8 WAFB in the 4 bud/spur treatment in 2010/11. This decrease in 'Sweetheart' was associated with significantly higher soluble solids and starch reserves in leaves, stem, trunk and roots 2-weeks post-harvest in trees thinned at dormancy, relative to trees thinned 8 WAFB. Fruit flesh firmness significantly increased with decreased crop load irrespective of time of thinning in 'Van' in 2010/11. In contrast flesh firmness was significantly higher in the 1 bud/spur treatment and similar between other treatments in 'Sweetheart' in 2010/11. In 2011/12 flesh firmness, soluble solids and colour significantly increased whilst fruit weight and TA significantly decreased 28 days post-harvest relative to at-harvest values. We found strong correlation between values obtained with the FirmTech II and the Guss fruit texture analyser. Sweet cherry fruit quality is optimised through attaining crop load of approximately 10 fruit per cm 2 of limb cross-sectional area through thinning at dormancy or full bloom.

The extended flowering period of many apple (Malus domestica) cultivars often causes problems in the management of crop load. Hydrogen cyanamide (Dormex ® ) was examined over a 2-year period for its effect on flowering, crop load, fruit size, and quality of 'Fuji' apple. In Year 1, hydrogen cyanamide was applied at 5 application times (40, 30, 20, 10, or 0 days before estimated budburst (dBEB)) at 3% v/v. These treatments were compared with an untreated control. In Year 2, hydrogen cyanamide was applied at 1%, 2%, or 3% v/v at either 40 or 30 dBEB. The blossom thinner ethephon was applied to all hydrogen cyanamide treated trees at full bloom. An untreated control, a hand-thinned treatment, and a chemically thinned control were also included. Hydrogen cyanamide advanced flowering in both years when applied at 40 or 30 dBEB. In Year 1, full bloom was advanced by more than 1 week and the flowering period from pink bud to full bloom compressed by the 40 dBEB application, resulting in a very clearly defined full bloom date. Application of hydrogen cyanamide at budburst or 10 dBEB resulted in extended flower development and some bud scorching. Unseasonally warm spring weather conditions in the second year resulted in an abnormally short flowering period. It would appear that under these conditions hydrogen cyanamide can still be used to advance flowering but is not necessary to compress the flowering period. Hydrogen cyanamide reduced fruit set in the first year but not the second. Most treatments showed no detrimental effect on fruit quality. There was no evidence of any negative interactions between HCN and ethephon.