Why Does My Oleander Shrub Look Unhealthy?

Are the leaves yellow and dry, drooping from the plant?

Did the leaves started yellowing at the middle and then spread outward?

Are there any swelled galls on the stems, bark, and leaves?

Do the leaves have moist or brown spots on them?

Did any of the branches blackened during a drought or after a prolonged freeze?

Are the leaves covered with small bumps?

Do the leaves and stems have white, cottony clusters on them?

Yur oleander is probably drought-stressed. Cultivate healthy plants by planting them in full sun, watering them in times of drought, and fertilizing them according to soil-test recommendations.

Oleander leaf scorch, mostly seen in California, is caused by a bacteria - Xylella fastidiosa. Bacteria are spread by the insect glassy-winged sharpshooter, which causes yellowing and drying of the leaves. Leaf scorch disease causes leaves to begin turning yellow from the outside edges toward the middle. Unfortunately, there is no cure for oleander leaf scorch and glassy-winged sharpshooters are hard to control.

Oleander knot is a disease caused by the bacterial pathogen Pseudomonas savastonoi pv. nerii. You can only prevent oleander knot by avoiding overhead irrigation and by pruning plants to remove dead and diseased stems and twigs. Disinfect your pruning tools between each cut in a solution of 1 part bleach to 10 parts water.

Your plant might be suffering from Anthracnose or some other fungal leaf spot. Spots may enlarge rapidly, especially in wet weather. Destroy infected leaves or plants. Spray plants with sulfur to prevent the disease from spreading, especially if the weather is wet. Prevent problems by thinning plants to provide good air circulation.

Botryosphaeria dieback is a fungal disease that attacks weakened oleanders after stress caused by drought or after a prolonged freeze. Prune off all dead and diseased branches. Disinfect your pruning tools between each cut in a solution of 1 part bleach to 10 parts water.

Leaves covered by small bumps are caused by scales. These tiny, shelled insects often feed on the undersides of the leaves, causing an unhealthy appearance with yellowish blotches on the upper leaf surfaces. Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

White, cottony clusters on leaves and stems are caused by mealybugs. These tiny insects are covered with a fluffy white coating. They feed by sucking plants sap. They produce sticky substance honeydew which makes leaves sticky. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

If the leaves are distorted and curled the culprits are aphids. These tiny insects cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted, and later leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.