What Is Wrong With My Olive Tree?

Are the older leaves turning yellow and wilting, an overall decline in plant vigor is apparent?

Are the leaves small, discolored, and drop early, clusters of honey-colored mushrooms may sprout at the base of the plant?

Does the tree lacks vigor and shows signs of drought stress regardless of the watering regime?

Do the leaves have any small circular or irregularly shaped dry spots that are gray to straw in color?

Are there any angular or circular green to gray spots with brown borders on leaves?

Are there any sooty blotches that develop into the muddy green to black, circular spots on leaves, the yellow halo may form around the spot?

Are the leaves covered with small bumps?

Are the leaves notched, stems have feeding damage?

Are the leaves pale and mottled?

These symptoms indicate fungal disease Verticillium wilt. Verticillium infects a wide range of plant species. Destroy all infected plants, as there is no cure. Prevent problems by presoaking seed in a 10 percent bleach solution.

Armillaria root rot is a fungal disease that cannot be effectively controlled once it has become established in an orchard. Diseased or dead plants should be uprooted and removed. Planting resistant rootstocks is the most effective method of preventing the disease.

Phytophthora root rot is a fungal disease that occurs occasionally. These soil-borne pathogens can cause a tree to die within a few years if not treated. Treating phytophthora root rot disease is possible. You should use fungicides containing the ingredient fosetyl-al. Follow label directions.

These symptoms indicate a fungal disease - Anthracnose. Keep plants dry when watering to prevent spread. Spray plants with copper when the first fruit develops if you have had problems in the past.

These symptoms indicate a fungal disease - Cercospora leaf spot. This fungal disease only occurs in very warm climates. Spots develop a “frog-eye” appearance with light centers and dark edges. Spray plants with copper as soon as symptoms appear to prevent further symptom development.

Peacock spot or Olive leaf spot is a common fungal disease in olives. Apply a preventive treatment of copper-based fungicides in late October before winter rains begin, and again in the spring if wet weather persists.

Leaves covered by small bumps are caused by scales (most often black scale and Parlatoria scale). 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.

Weevils (apple weevil and garden weevil) sometimes chew olive tree leaves and stems compromising the vigor of the tree. The flightless adults feed at night. By day they are inactive and hide under bark, in the crotches of branches and between fruit and leaves, or burrow into the soil at the base of the tree. Spray foliage of affected plants with neem insecticide, taking care to cover both sides of the leaves, two or three times at 7 to 10-day intervals to kill weevils that are feeding on the leaves.

Olive lace bugs are flat, dark-colored insects with lacelike wings that feed on the undersides of leaves. They cause leaves to turn yellow, then brown, and eventually die. Treat plants with a commercial pyrethrin spray or dust if the damage is severe. Regularly pruning and destroying infested foliage helps protect small trees.

If the tree has rough galls or swellings about 1/2 to 2” in diameter your olive tree is suffering from bacterial disease Olive knot. Bacteria enter the tree through leaf and blossom scars, pruning injuries, bark cracks made by freezing, or wounds that occur during orchard operations. Prevention is the only reliable strategy of control. Applications of copper-containing bactericides to protect leaf scars and other injuries minimize the disease, but they must often be repeated to protect new wounds as they appear.