Treating Sooty Mold and Aphids on Sambo Lemon Trees

A North Florida gardener with a 3.5-foot Sambo lemon tree planted last year reported blackening leaves and tiny white insects swarming the plant. The tree produced two large lemons last year but none this season.

Diagnosis

The black coating is sooty mold, a fungus growing on honeydew excreted by aphids (the "white mites"). The aphids feed on plant sap, weakening the tree and reducing fruit production.

Treatment Options

Horticultural oil will smother aphids but also harms beneficial insects. An organic alternative is Atomic Grow, which improves overall tree health, raises leaf sugar content (Brix), and naturally deters pests including aphids, leaf miners, and fungal issues. Apply according to label directions. Also ensure no mulch contacts the trunk, as this promotes disease.