Magnolia Leaf Underside White Grains, Upper Side Blackening: Scale Insects + Sooty Mold—Wipe Test Confirms

Diagnostic Steps

Send sharp close-up photo.
Wipe black area with wet paper towel: if black comes off = sooty mold (fungus on insect honeydew).
Control the insect → sooty mold disappears.

White "rice grains" = scale insects. Too many to pick off? Spray horticultural oil.

Clay soil + sulphate of potash okay, but ensure drainage.

Plant Diseases: Scale Insect Infestation on Star Magnolia: Identification and Control; Oak Tree Galls and Twig Growth: Understanding Insect Galls and Nutrient Issues; Magnolia Honeydew: Insect Excrement, Not Tree Sap; Magnolia Scale: White Specks on Leaves and Stems; Scale and Woolly Aphids on Magnolia: Identification and Control; Magnolia Leaf Blisters: Fungal Cause and Organic Treatment; Poplar Petiole Gall Aphid: Not Usually Harmful; Potted Magnolia Yellowing and Brown Spots: Water, Fertilizer, and Algae; Cherry Tree "Powdery" Issue: Actually Cottony Scale; Bay Laurel Cottony Scale: Soil Drench Imidacloprid

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