Bacterial Disease Prevention
Begins Before Planting
For most fungal and bacterial diseases in almonds, disease prevention begins by selecting disease-resistant varieties and rootstocks before planting, and planting in areas without previous almond disease problems.
Additional recommendations include:
- Avoid planting in low areas, or areas with a history of standing water.
- Develop an irrigation system that is designed not to wet tree leaves.
- Avoid prolonged irrigation sets that lead to standing water.
- Manage a nitrogen fertilization program to avoid excessive nitrogen, which can promote some major almond diseases.
- Use management techniques and cultural practices that promote strong, healthy trees that can resist diseases.
- Avoid the transfer of disease organisms from one area to another via equipment and/or personnel.
There are several bacterial diseases that can impact almond trees; almond leaf scorch and bacterial canker are the most common.
Almond leaf scorch
Almond leaf scorch was first discovered in Southern California in the 1930s. Researchers determined the disease was caused by a bacterium in the water-conducting vessels of almond trees. It was spread by certain leafhoppers and spittlebugs. Glassy-winged sharpshooter is a known vector of ALS. The disease appears as a marginal scorching of leaves that begins as early as June and continues to develop during summer. A golden yellow band develops between the brown necrotic edge and the inner green tissues of the leaf. Disease symptoms may appear first on one branch or a portion of one scaffold. As years go by, more and more of the tree is affected until the whole canopy is involved.
Bacterial canker is found in all almond growing regions of California. The cankers can be found on trunks, scaffolds or small branches. Pseudomonas syringae survives on plant surfaces, is spread by splashing rain, and is favored by high moisture and low temperatures in spring. The disease occurs almost exclusively in orchards where almond or other Prunus spp. orchards previously existed. The disease is worse in low (cold) or sandy spots with high populations of ring nematode. Nitrogen deficient trees are most prone to bacterial canker as are young trees that are 2 to 8 years old. The disease rarely occurs in the first year of planting and is uncommon in nurseries.
In collaboration with Western Farm Press magazine, The Almond Board of California created an e-learning course on disease management in almonds
UC IPM Almond Fungicide Resistance Management
UC IPM Pest Management Guidelines
Seasonal Guide to Environmentally Responsible Pest Management Practices in Almonds