Copper is an essential nutrient for plants, playing a critical role in various processes, including photosynthesis, respiration, and enzyme activation. However, many fruit growers in Washington State have been experiencing wither tip or copper deficiency in their apple and pear orchards, which can significantly impact tree health and fruit quality.
Copper deficiency typically occurs when there is a lack of copper in the soil, which can happen due to leaching, reduced availability, or high soil pH. Symptoms of copper deficiency usually appear on the terminal leaves of the tree around mid-June, with the leaves turning yellow, wilting, and falling off. The bark may also crack and become rough.
Fortunately, copper deficiency can be treated effectively with post-harvest foliar applications of copper sulfate or basic copper sulfate. A typical recommendation is to apply one pound of copper per acre, which should correct the symptoms. However, if the deficiency is severe, mid-season sprays of copper chelate or basic copper sulfate products may be required, but these may cause foliage and fruit injury. It is essential to be cautious when applying copper products, as they are potentially phytotoxic and can cause severe fruit russetting, especially on Anjou.
One way to prevent copper deficiency is to incorporate copper into the zinc dormant sprays. However, adding copper to zinc sprays will not increase leaf copper levels significantly. Therefore, it is essential to apply copper-specific treatments to address copper deficiency. It is also crucial to avoid excessive copper application, as it can increase soil copper levels to toxic levels for fruit trees.
In conclusion, copper deficiency or wither tip is a common problem among Washington apple and pear orchards, causing significant damage to tree health and fruit quality. However, with the right treatment and caution, copper deficiency can be effectively managed, ensuring healthy tree growth and high-quality fruit production. So, if you're growing copper-bearing trees in Washington, keep an eye out for copper deficiency symptoms and take proactive steps to address them early.