Broccoli Thunder Dome White Cottony Spots - Causes & Fixes

Jump to cause: Powdery Mildew Mealybug Infestation Sclerotinia (White Mold)

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Powdery Mildew

This fungal disease, caused by Oomycetes like Peronospora parasitica, thrives in high humidity and cool temperatures common for broccoli. It creates characteristic white, flour-like patches on the leaves that can eventually lead to leaf necrosis and stunted head development.

Very Common

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How to confirm: Inspect the underside of the leaves to see if the white coating is spreading across the leaf surface.

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1 Apply an organic fungicide to the affected leaves to stop the spread of the fungal spores.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

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2 Prune and remove any heavily infected leaves to prevent the disease from spreading to healthy parts of the plant.

3 Improve air circulation around the broccoli plants and avoid overhead watering to reduce the humidity that fuels mildew growth.

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Mealybug Infestation

Mealybugs are small, soft-bodied insects that secrete a white, waxy, cottony substance to protect themselves. They feed on the sap of the broccoli plant, which can cause yellowing and wilting of the leaves.

Common

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How to confirm: Check the leaf axils (where the leaf meets the stem) for tiny, moving white insects.

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1 Isolate the affected broccoli plant immediately to prevent the mealybugs from spreading to other plants in your collection.

2 Apply an organic insecticide spray to the plant to eliminate existing insects and their eggs.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

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3 Use a cotton swab dipped in isopropyl alcohol to manually remove visible white cottony clusters from the stems and leaves.

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Sclerotinia (White Mold)

This soil-borne fungus attacks the stems and base of brassicas, producing a thick, white, cottony mycelium. It can cause the plant to collapse and die rapidly if it infects the crown.

Common

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How to confirm: Examine the base of the broccoli stem for any signs of mushy, decaying tissue underneath the white growth.

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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 to healthy plants.

2 Apply a fungicide to protect remaining healthy tissue and manage the fungal spread.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

3 Improve air circulation around the base of the plant and ensure the soil is not overly saturated to create a less hospitable environment for mold.