Brown Spots in Pear and Apple Flesh Could be Lack of Calcium

Do you have an apple or pear tree that is about 10 or 12 years old, giving you delicious looking fruit ball when you bite or cut into the fruit, you see corky, brown spots in the flesh? If you do, this could be a sign that your fruit trees will need to be sprayed with calcium when the fruit is young and during its formation.

Corky spot in Keiffer pear

This disorder is called bitter pit in apple but called corky spot when it occurs in pear. The root of the problem is the same; not enough calcium getting from the soil to the developing fruit. Established fruit trees take a lot of nutrients out of the soil each year for the developing fruit. It would seem unlikely in our desert soils that are full of calcium that a lack of calcium would be a problem. But it can be.

Established fruit trees continually mine nutrients from the same areas of the soil each year. Once a tree becomes established where irrigations are limited to a certain area, the root systems do not continue to explore the surrounding soil. They continue to mine these elements where they are.

Corky spot in Comice pear

Calcium is relatively insoluble. In other words, even though there is plenty of this element in the soil it does not easily dissolve into the applied water before it is taken up by the plant. Producing fruit, and a lot of it, draws heavily on the supply of calcium the tree can find in the soil. Over years the available calcium supply diminishes. If the soil does not allow calcium to dissolve when the plant needs it, calcium deficiencies occur.

If you look closely at the fruit there can be telltale indicators that bitter pit or corky spot is present without cutting into the fruit. I look for dimples in the skin. If you look closely at these dimples you will see that they do not “ripen” or turn from green to its mature color like the rest of the skin. If you don't look closely, you will miss it.

Greenish dimples on the surface of the fruit can be a dead giveaway that corky spot or bitter pit has affected the fruit. Cutting the dimple away will expose the corky spot just under the surface.

Normally this calcium deficiency occurs on some apples and some pairs but it is less likely on others. In our climate in the Las Vegas Valley I have seen it develop on Mutsu apple and Anjou, Comice and Keiffer pears.

To remedy the problem you will need to spray on the fruit as it is developing, calcium sprays. I usually buy food-grade or aquarium-grade calcium chloride. I dissolve about 3-5 pounds of calcium chloride in 100 gallons of water. To convert, there is 16 ounces or 454 grams in one pound.

Dissolve the calcium chloride thoroughly in warm water and add a liquid detergent or some sort of spreading agent to help the calcium entry through the skin of the fruit. Spray on the fruit as soon as you see the fruit beginning to develop. Make five applications of the spray about one week apart. Avoid spraying when temperatures are high. Spray in the early morning hours. Real wedding the fruit lightly with pure water after the spray has dried will help more of the calcium to enter the fruit.

These five applications of calcium chloride applied along with a sticker/spreader when the fruit is still young will help to prevent bitter pit or corky spot from developing.