Olive pests and leaf spots: what to check

Inspect for olive-scab spots that are circular and purple or brown with a yellow or purple halo, and for scale coverings or sticky honeydew with sooty mold. These are distinct observations, not one explanation for every olive mark.

Check both leaf surfaces, young twigs, and fruit where present. Note whether spots have halos, whether scale is a fixed gray or black covering, whether honeydew or ants are present, how wet the foliage has been, and whether leaf fall is premature.

Olive scab causes leaf spots and premature leaf fall. Armored scales have fixed coverings and do not produce honeydew. Black scale is a soft scale that releases honeydew, on which sooty mold can grow. Identify the pest before treating it.

Start with inspection and hygiene: remove fallen diseased leaves and debris, prune clearly affected twigs with clean tools, improve airflow, and avoid prolonged wet foliage. Isolate visible scale while you check what it is.

After removing debris or isolating a plant with suspected scale, recheck new leaves, leaf undersides, and twigs for new spots, coverings, or sticky residue. Keep checking until nothing new appears.

Olives grow well in containers and under glass, but most scale control is worked out for orchards and gardens. Judge indoor pest levels, humidity and treatment timing plant by plant.