Bitter pit is a disorder of apple fruit caused by a deficiency of calcium, and symptoms are usually seen after harvest. Most varieties can get bitter pit, but Granny Smith, Jonathan, Honey crisp, Northern Spy, Gravenstein, Cortland, Fuji, Crispin, Empire, Idared, and Delicious are a few susceptible varieties. Rome Beauty, Winesap, Macintosh and Gala 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
- during irrigation season, avoid wide fluctuations in soil moisture
- do not over-fertilize, as vigorously growing trees with over-sized fruit are more susceptible
- do not over-prune in winter
- do not over-thin in spring
- keep trees at annual bearing through proper thinning and pollination practices
- harvest at optimal timing because late harvested fruit is prone to bitter bit
- calcium sprays (calcium chloride, calcium nitrate, STOP-IT, Nutri-Cal, Miracal, etc.) should be applied monthly throughout the growing season only if the above practices do not alleviate the problem