Apples

Boron deficiency in apples

Boron is an essential nutrient for all plants. Fertilizing apple trees with adequate boron is necessary for:

• Flower formation
• Fruit development
• Tree growth

Boron deficiency commonly causes cracking and external cork symptoms on the fruit. This may occur even though the foliage shows no symptoms, such as rosetting of thickened brittle leaves and dieback of the growing points. Boron deficiency causes premature fruit drop, and fruit quality can be badly impaired by the cork formation. If the internal cork develops early in the season, the affected fruit will become badly deformed.

In severe cases, dead areas appear in the bark of young branches (apple measles). The bark may be rough and cracked. Boron deficiency may affect the movement of calcium from the tree leaves to other tissues. As a result, boron deficiency often is associated with "bitter pit."

Applying boron fertilizers has been shown to increase yields and improve the quality of a wide variety of crops. Apples respond well to the correct amount of fertilizers. However, applying too much boron to apples can cause toxicity, so soil testing and leaf analysis is critical to determine the extent of boron deficiency.