The Q&A Archives: Rust Spots on Citrus

Question: My young citrus trees have what looks like rust spots on the underside of the leaves. What causes this?

Answer: If you're sure it's a spot and not a scale insect, the probable cause is a fungus, a problem that occurs when trees are planted in poorly drained soils. Citrus likes moist soil, but not soggy or waterlogged soils. Try to control by watering deeply, but less frequently than you have in the past.

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