What Causes Oleander Leaves to Die?

Irrigating oleander plants in the morning reduces the chance of leaf spot.

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Oleanders (Nerium oleander) are evergreen shrubs reaching heights of 12 feet. Gardeners prize these ornamental plants for their colorful summer blooms. Unfortunately, oleanders can become infested with pests and diseases that cause foliage to die off. Nutrient-sucking pests, leaf spots, leaf scorch and nutritional problems may cause oleander leaves to die off. Using cultural and chemical treatment options prevents oleanders from succumbing to leaf damage.

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Nutrient-sucking pests, such as aphids, mealybugs and scales, invade oleander shrubs. These pests suck sap from the foliage, which causes death. Other nutrient-sucking pest infestation symptoms include leaf yellow, curling and defoliation. In addition, nutrient sucking pests produce a sticky substance called honeydew, which coats foliage and branches. Fungal spores floating in the air stick to the honeydew. The result is an oleander shrub covered in a black powdery substance. Treating pest-infested oleanders with insecticidal soap reduces the pest population.

Leaf Spots

Numerous different fungi species cause leaf spot disease. Signs of leaf spot are raised bumps covering foliage, discoloration, leaf death and defoliation. Prevent leaf spot by watering oleander shrubs at the dripline. The dripline is the area that is directly underneath the outermost foliage. Clean up infected debris underneath their oleander shrub. Burn or throw away diseased debris. Do not compost infected debris.

Leaf Scorch

Oleander leaf scorch is a lethal disease that kills off plants within 2 years of infection. Bacteria called Xylella fastidiosa causes disease, which is transmitted to plants by glassy-winged sharpshooter insects. Insects infect oleander plants when they feed on its foliage. Infected plants exhibit symptoms including leaf tip discoloration, dead leaves and branch dieback. There is no cure for oleander leaf scorch. Infected shrubs must be removed from the landscape.

Nutritional Problems

Oleanders suffering from nutritional problems display signs such as leaf yellowing, branch die back and defoliation. Gardeners may notice their plants produce light-colored growth. Fertilizing plants with balanced fertilizers containing nitrogen, phosphorous and potassium prevents and treats nutritional problems. Use 2 pounds of nitrogen, phosphorous and potassium per 1,000 square feet that are occupied with roots, as suggested by the International Oleander Society. Watering the area after distributing fertilizer helps the nutrients sink into the soil, so that they are accessed by the root system.

ReferencesUniversity of Arizona Extension: Oleander Leaf ScorchUniversity of California: Leaf SpotUniversity of California: OleanderInternational Oleander Society: Oleander CulturePhoto Credit Thinkstock/Comstock/Getty ImagesRead Next:

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