Investigating Yellowing Leaves and Scale on Meyer Lemon in Hawaii

Investigating Yellowing Leaves and Scale on Meyer Lemon in Hawaii

Two Meyer lemons in Hawaii: one has yellowing leaf undersides, the other has scale on fruit (from stem to mid-fruit). Citrus fertilizer used, plenty of water.

Possible Issues

• Nutrient deficiency: Yellowing undersides may indicate nitrogen, iron, or magnesium shortage—common in high-rainfall, leached soils.
• Scale insects: Armored or soft scale on fruit and stems. They suck sap, weaken tree, and secrete honeydew (sooty mold).
• Root problems: Overwatering or poor drainage can cause yellowing despite "plenty of water."

Next Steps

1. Take close-up photos of leaf yellowing and fruit scale (in focus).
2. Bring samples to a local nursery for hands-on ID—physical samples reveal details photos miss.
3. Check soil drainage: Dig a hole, fill with water; should drain in <1 hour.
4. Consider soil test for pH and nutrients.

Treatment Preview

• Scale: Horticultural oil sprays (3× at 2-week intervals).
• Nutrients: Foliar chelated iron/magnesium + balanced slow-release citrus fertilizer.
• Watering: Deep, infrequent irrigation; let top 2–3 inches dry between waterings.

Local expertise is invaluable for tropical citrus issues.