Brassica rapa White Cottony Spots - Causes & Fixes

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Powdery Mildew

A fungal disease caused by Oomycetes that manifests as white, flour-like patches on the surface of leaves. In Brassica species, it thrives in high humidity and moderate temperatures, eventually causing leaf yellowing and stunted growth.

Very Common

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How to confirm: Inspect the underside of the leaves to see if the white powdery coating spreads across the leaf veins.

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1 Apply an organic fungicide to the affected leaves to eliminate the fungal spores and prevent further spread.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

2 Prune and remove any heavily infected leaves immediately, ensuring you dispose of them away from your garden to prevent reinfection.

3 Improve air circulation around your Brassica plants and reduce overhead watering to lower humidity levels around the foliage.

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Mealybug Infestation

These small insects secrete a white, waxy, cottony substance to protect themselves. They feed on the sap of the turnip or pak choi, often congregating at the base of the leaves or near the stem.

Common

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How to confirm: Use a magnifying glass to check for tiny, slow-moving insects hidden within the white patches.

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shopping_cart Recommended Products

1 Isolate the affected plant immediately to prevent the mealybugs from spreading to your other brassicas.

2 Apply an organic insecticide spray to the plant, ensuring you coat the undersides of leaves and the stem base where insects hide.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

3 Use yellow sticky traps near the plant base to capture any flying adult mealybugs and monitor the infestation levels.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

In Stock

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Sclerotinia sclerotiorum (White Mold)

This soil-borne fungus produces dense, white mycelium that looks like cotton spreading across the plant tissue. It can quickly cause the stems of Brassicas to rot and collapse.

Common

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How to confirm: Check the base of the plant for any firm, dark brown or black sclerotia (seed-like structures) embedded in the white fluff.

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shopping_cart Recommended Products

1 Immediately remove and destroy all infected plant material and surrounding debris to prevent the fungus from spreading through the soil.

2 Apply an organic fungicide to the affected area to control the spread of the white mold.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

3 Improve air circulation and reduce moisture around the base of the plant by using a well-draining potting medium mixed with perlite.