|Keiffer pear with outside evidence of Corky spot With the small green dimple in the center of the fruit|
A. Corky spot in pears appears as brown areas, about the size of a small marble or smaller, in the flesh of the fruit. These spots are surrounded by healthy flesh. On the outside skin it is hard to see but often it is slightly sunken and frequently some green remains after the fruit ripens.
The flesh is not rotten. The cells in the flesh do not have enough calcium for good development and they die and are brown. These spots do not taste good and are usually dry. But if you eat them it’s not a problem and will not harm you.
|Corky spot on the interior flesh of Keiffer pear.|
My experience with this “disease” is that it develops on pears grown on older trees, usually over ten years of age. I theorize that the roots of the tree have exhausted the calcium in the soil surrounding them. The soil is full of calcium, but it cannot release it fast enough as the fruit develop.
|Corky spot on Comice pear growing in the Mojave Desert|
What to do? Applications of calcium to the soil are not 100% effective. It is recommended that the fruit on the tree is sprayed with a liquid calcium solution as the fruit is enlarging. The most effective sprays are made with 5% calcium chloride dissolved in water. The calcium chloride should be food grade.
|5% solution of Foodgrade calcium chloride will work as a foliar spray. This foodgrade calcium chloride is for homebrewing|
These spray applications are made five times, at least a week apart, as the fruit enlarges. Direct the sprays mostly at the fruit. Leaf sprays are less important.
Not all pears are affected equally. Some pears appear to handle low soil calcium levels better than others. The problem may also vary with different types of soils. Watch for it on older pear trees.By the way, this disorder also affects some apples. When it does, it is no longer called “Corky Spot” but “Bitter Pit” instead.