This year has been an extra wet one. Winter of 2019 brought heavy snow in the mountains, leading to a lot of run-off during the spring melting season. On top of that, spring brought more rain than usual.

All of this moisture has had a notable impact on landscapes in California. Trees, for instance, are far more prone to fungal and bacterial diseases when conditions have been wet. Here are three tree diseases to watch out for after a particularly wet spring like this one.

1. Bacterial Leaf Spot

Two primary types of bacteria can cause bacterial leaf spot disease: Pseudomonas spp. and Xanthomonas spp. This disease occurs not only on trees, but also on garden plants like beets, peppers, and tomatoes. The bacteria thrive in moist conditions and can spread from garden plants to your trees.

If you notice signs of bacterial leaf spot on your garden plants, consider removing the plants rather than risk having the disease spread to your trees.
The main symptom of leaf spot disease is the appearance of spots on the tree’s leaves. The spots usually first appear on the bottom of the leaf. They slowly grow, eventually reaching the leaf veins. Once this occurs, some leaves may shrivel up and fall from the tree.
No recognized chemical control measures exist for bacterial leaf spot, but you have ways to manage the disease mechanically. Trim your trees to encourage air circulation and light penetration through the canopy. When you water your trees, make sure you do not get the leaves wet, and avoid applying fertilizer until the disease clears up. Rake up any fallen leaves promptly.
If you follow these practices, you should notice a gradual reduction in symptoms over the coming months and years.

2. Brown Rot

If you have fruit trees, such as apricots, peaches, or cherries, on your property, then you need to be aware of brown rot. Caused by the fungus Monilinia fructicola, brown rot causes shoots, twigs, blossoms, and fruit to develop soft, brown lesions. Once the fruit has been affected, it starts to rot and become fuzzy. Sometimes the fruit falls to the ground; other times, it remains on the tree and hardens.

Once a tree has brown rot, you can’t save the fruit that year. However, you should take action to ensure the next year’s fruit is edible. Have a tree care company prune away all of the affected branches. The branches must be disposed of properly to keep the disease from spreading. Rake up all fallen fruit promptly. Next spring, spray your fruit trees with fungicides at the pink-bud stage.

3. Citrus Scab

If you have an orange, grapefruit, or other citrus tree on your property, watch it for signs of citrus scab after a wet spring. Citrus scab happens because of the fungus Elsinoë fawcettii. It causes the leaves and the fruits themselves to develop raised, pimple-like bumps. These bumps may be creamcolored or dark brown in color. They tend to be most prevalent on the undersides of leaves.

Symptoms of citrus scab can appear seemingly overnight. If you manage to treat the tree with copper-based fungicides as soon as fruit appears on the tree, you may be able to prevent citrus scab from spreading from the leaves to the fruit.
Going forward, prune your tree regularly to encourage better air movement through the leaves. Dry leaves are less appealing to fungus. Also, spray your citrus trees regularly in the spring as a preventative measure.
This wet spring has been hard on a lot of trees and plants. If you suspect your trees may suffer from one of the conditions above, contact Community Tree Service. We offer comprehensive trimming and pruning services to help get your trees back on track.