Pecan Leaf Blotch: A Common Fungal Disease
Introduction
Pecan leaf blotch is a common fungal disease that affects pecan trees. It is caused by a fungus called Mycosphaerella dendroides. While it is generally not a major concern for healthy trees, it can become a problem if the tree is already weakened by other diseases.
Symptoms of Pecan Leaf Blotch
The symptoms of pecan leaf blotch first appear in June and July. They primarily affect older foliage and weak or frail trees. The first signs of the disease are small, round, green velvety spots on the underside of mature leaves. On the upper surface of the leaves, pale yellow blotches appear.
As the disease progresses, by midsummer, black raised dots can be seen in the leaf spots. This is a result of wind and rain whisking away the fungal spores. The spotting then runs together to form larger, shiny black blotches. Small leaflets may also develop spots and drop from the tree.
In severe cases, the nuts will ultimately turn black and display indented spots. The tree’s foliage will drop prematurely in late summer to early fall. Once the nut has become entirely black, it too will fall from the diseased portion of the tree.
Effects of Pecan Leaf Blotch
Not only are the fruits wasted, but severe pecan leaf blotch infection can also result in a decline of the tree’s vitality and a weakened resistance to other diseases.
Controlling Pecan Leaf Blotch
There are several steps you can take to control pecan leaf blotch:
- Clean up fallen leaves: The fungus that causes pecan leaf blotch can overwinter in fallen leaves. To prevent the disease from spreading, clean up leaves before winter sets in and remove old fallen foliage in early spring just as the frost is thawing.
- Choose disease-resistant trees: When planting a new pecan tree, consult with your local nursery experts to choose a variety that is known to be resistant to pecan leaf blotch.
- Use fungicides: Fungicides can be used to treat pecan leaf blotch. It is best to contact your local agricultural extension agency to learn about your options and the proper application methods.
Additional Tips
- Spray the tree with a fungicide after it has pollinated. A good way to tell if this has happened is that the nutlet tips will have turned brown.
- Apply a second spraying about a month later.
- Inspect your trees regularly for signs of pecan leaf blotch and take steps to control the disease as soon as possible.
By following these tips, you can help to keep your pecan trees healthy and productive.
