Identifying Fruit Problems on Meyer Lemon Trees

A Meyer lemon tree with small holes in the fruit skin, followed by black, moldy pith, indicates a pest or disease issue—not the whitefly problem previously treated. The holes suggest insect feeding, while internal mold points to secondary fungal infection entering through the wounds.

Possible Causes

• Citrus fruit borers: Moth larvae (like citrus peelminer or fruit fly larvae) tunnel into young fruit, creating entry points for pathogens.
• Poor pollination: Inadequate pollination can cause fruit to develop abnormally and rot from the blossom end. Check cut fruit for seeds—seedless fruit often indicates pollination failure.
• Fungal diseases: Alternaria brown rot or Phytophthora can infect fruit through injuries or natural openings, especially in humid conditions.

Diagnostic Steps

Cut open affected fruit to check for larvae, frass (insect droppings), or seed development. If no insects are found, the issue may be physiological or fungal. Photographs of the fruit, tree canopy, and any visible pests can help with remote diagnosis.

Management Strategies

• Sanitation: Remove and destroy all infected fruit from the tree and ground to reduce inoculum and pest populations.
• Insect control: If borers or fruit flies are confirmed, apply appropriate insecticides timed to egg-laying periods (often after petal fall). Spinosad or kaolin clay are lower-toxicity options.
• Fungicide applications: Copper-based fungicides or phosphorous acid products can protect fruit from fungal infections when applied preventively.
• Cultural care: Ensure proper irrigation (avoid overhead watering), fertilization, and pruning for air circulation.

Since the exact cause isn't clear from the description alone, close observation and possibly submitting samples or photos to a local extension service will yield the most targeted treatment plan.