Calcium management is critical to control bitter pit, especially for susceptible varieties. Good management should always be systems-based starting with adequate supplies in the soil, good tree and root health, sufficient water to move calcium into the plant and appropriate crop load management. Supplemental calcium sprays are important during early fruit development. Start in early June for best effectiveness. The following recommendation comes from the WSU Crop Protection Guide.
Calcium (bitterpit of apples): The per season recommendation of actual Ca is 5 to 15 lbs which equals 15 to 50 lbs of calcium chloride per acre per season.
0.5 to 1.3 lbs actual calcium per acre per application (2 to 4 lbs calcium chloride/A per application). Make 6 to 12 applications from early June to late August.
Calcium in the form of calcium chloride is recommended because of its proven effectiveness and lower cost. Often early season sprays are liquid calcium products which tank mix easier. Make sure that the liquid and calcium chloride applications you use combined equal the total per season goal.
See Penn State Extension’s useful calculator for comparing calcium chloride to other sources of calcium, as it is important to make sure you develop a season-long program for applying sufficient total amounts of elemental calcium.
Rate Recommendations Actual Ca lb/A PER SEASON
|Actual Ca lb/A||Expected Results|
|4-5||This is the lowest rate that should be used. It will give some control of bitter pit and corking, will cause no leaf burning, and is not likely to enhance storage.|
|6-8||Should give good control of preharvest physiological disorders. It should not cause any significant leaf injury and will probably not enhance fruit storage life.|
|9-11||Should give excellent control of corking and bitter pitting, and should be the intermediate rate. It may enhance fruit storage life and should result in almost no leaf injury.|
|12-14||The highest rate that should be used. Should give outstanding control of corking and bitter pit. May result in some enhanced storage life.|
Table courtesy Dr. Rob Crassweller, Penn State Extension.
WSU Extension Specialist, Tree Fruit
(509) 663-8181 ext 211
WSU Tree Fruit Physiology
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