Bitter pit is a disorder of apple fruit caused by a deficiency of calcium, and symptoms are usually seen after harvest. Granny Smith, Jonathan, and Golden Delicious are a few susceptible varieties. Rome Beauty, Macintosh, Gala, and Fuji are less susceptible. Affected apples will have sunken lesions on the skin, with brown, spongy tissue underneath.
Bitter pit and late-season stinkbug injury look similar. Bitter pit lesions are usually distributed on the sides and bottom of the apple and are circular in shape. Lesions become worse after storage, turning dark brown to black.
Stink bug injury is usually located higher on the fruit (near the stem), is conical or rectangular in shape, and turns the flesh light tan to dark brown.
Bitter pit usually occurs on trees with low fruit set, excessive vigor, irregular soil moisture, or on certain varieties. The varieties listed above are the most susceptible, although almost any young, extremely vigorous tree may exhibit symptoms.
- Brown, sunken lesions on the skin
- Brown, spongy tissue below the skin surface
- Maintain trees at a moderate level of vigor
- Do not over-fertilize, as vigorous trees can be more susceptible
- Maintain even soil moisture
- Do not over-thin
- Keep trees at annual bearing
- Do not excessively prune at dormancy
- Prune in summer to remove excess growth