Has your Granny Smith got black spots or is your Golden Delicious not totally golden then you may have bitter pit. This is not a fungal or insect borne disease but a chemical imbalance.
Bitter Pit is a problem with the fruit on Apple trees caused by a shortage of Calcium. The fruit have dark, sunken spots on the surface, browning flesh and a slightly bitter taste. The problem can continue or start developing after harvest so inspect stored apples.
Causes of Bitter Pit
- Dry conditions can reduce the calcium uptake even if it is present
- Vigorous trees with copious leaf area need more calcium. Bramley’s Seedling and Newton Wonder are large fruiting cookers that are prone to the problem.
- Trees without adequate Calcium will rob fruit of the calcium to sustain other parts of the tree.
Treatments of Bitter Pit
- Install irrigation to give tree roots access to moisture and natural calcium.
- Add lime or chalk to the ground then rake and water in.
- Spray the fruit from June onwards with Calcium nitrate or Calcium chloride solution.
- Do not store apples showing signs of bitter pit. Rather eat or cook with them asap.
- Mulch to keep soil in good heart.
Read about other Apple problems and control
Cork spot and Jonathan spot are similar to Bitter pit in that damage to tissue occurs mostly on the surface and just below. Although apples affected with these disorders are still edible they are unattractive in appearance.