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Calcium Deficiency (bitter pit) in AppleCalcium deficiencies contribute to certain fruit disorders including bitter pit, internal breakdown, storage rots, cork spot (Anjou pit), and alfalfa greening. Jonagold and Golden Delicious are particularly sensitive to bitter pit development. The need for calcium sprays is not predictable from soil or leaf analysis. Calcium chloride sprays alone can not be expected to eliminate calcium related fruit disorders. Cultural factors can influence calcium nutrition (see cultural controls).
Bitter Pit of Apple, Cork Spot (Anjou Pit) and Alfalfa Greening of PearsBitter pit on apples shows as small pits that resemble miniature bruises. The skin within the pit is grey, brown or black and the flesh beneath is dry, brown and spongy. Bitter pit is most common on vigorous trees bearing light crops and is especially common on large fruit. The symptoms may show in the orchard but more frequently they become apparent after picking. Bitter pit is a disorder that results from an inadequate supply of calcium to developing fruit.
Cork spot, often called Anjou pit, affects only Anjou pears. Pears develop a bumpy, uneven surface as they approach maturity. Affected areas turn yellow and soften prematurely. The flesh beneath the depressions is soft and turns brown or grey. Anjou pit occurs most seriously in seasons when hot, dry weather precedes picking. Cork spot is a disorder that results from inadequate supply of calcium to developing fruit. Alfalfa greening (Green stain) affects only the Anjou variety of pears. Fruits develop dark green, slightly sunken areas on the skin shortly before picking. Alfalfa greening is a physiological disorder, most likely caused by a nutritional imbalance between calcium and nitrogen, and excessive irrigation. Control of Calcium Related DisordersCultural
ChemicalCalcium chloride sprays can be expected to reduce the incidence of many calcium deficiency disorders in fruit.Apples - Apply calcium chloride (food grade, 27% calcium) sprays at 8-12 kg/ha (3.3-4.9 kg/acre) or 500 g/100 L (2.27 kg/100 gal) at 10 day intervals beginning mid July. Lower rates cause less leaf burning but should be applied more frequently to be similarly effective. Aim for a total application rate of 36 kg/ha (15 kg/acre) per orchard per year. Apply COR-CLEAR (34.5% calcium) at 6.3-9.4 kg/ha (2.6-3.8 kg/acre) in 500-2500 L/ha (200-1000L/acre) of water for concentrate applications. For dilute applications, use 0.4kg/100L of water. Aim for a total season application rate of at least 28 kg/ha (12kg/acre). For specific recommendations, consult your fieldman or horticultural consultant. WARNING - Application of calcium chloride almost always causes non-serious burn of leaf edges but severe leaf and fruit injury is possible under some conditions. To reduce the chance of severe injury, be careful not to exceed recommended rates. Do not apply the spray under wet, humid, or slow drying conditions. Spraying when temperatures are high may also produce injury. Although the safe upper temperature limit is not known, it is suggested that damage may occur at about 27 oC. In hot weather, growers should apply the spray during the coolest part of the day.
Pears - Calcium chloride (food grade, 27% calcium) should be applied as a high volume spray of 400 g/100 L (1.8 kg/100 gal) with a surfactant. Do not apply at the apple rate as this may result in leaf and/or fruit burn. Apply three or more sprays at 2-week intervals beginning mid-May. Apply COR-CLEAR (34.5% calcium). For dilute applications use 0.4 kg/450L of water. Apply COR-CLEAR at up to 4.5 kg/ha (1.8 kg/acre). For specific recommendations, consult your fieldman or Horticultural consultant. For more information consult the BCMAFF Tree Fruit Production Guide.
Return to Tree Fruit Pests and Diseases
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