Brassica oleracea botrytis White Cottony Spots - Causes & Fixes

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Sclerotinia sclerotiorum (White Mold)

This fungal pathogen produces a characteristic white, cottony mycelium that can rapidly envelop cauliflower heads and stems. It thrives in cool, moist conditions and often leads to stem decay and eventual collapse of the plant.

Very Common

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How to confirm: Check the base of the plant or the curd for small, hard, black structures called sclerotia embedded in the white fuzz.

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1 Immediately remove and destroy all infected plant material and surrounding debris to prevent the spread of fungal spores; do not compost this material.

2 Apply an organic fungicide to the remaining healthy plants to control the spread of the white mold.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

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3 Improve air circulation and reduce moisture by thinning plants and avoiding overhead watering, ensuring the soil stays well-drained.

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Botrytis cinerea (Gray Mold)

While often appearing gray, early stages of Botrytis can present as white, fuzzy patches on the cauliflower curd. This fungus attacks the tender tissues of Brassica oleracea, especially in high humidity.

Very Common

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How to confirm: Inspect the spots to see if they transition from white to a brownish-gray color with visible spore masses under magnification.

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1 Remove and destroy all infected cauliflower curds and surrounding plant tissue immediately to prevent fungal spores from spreading to healthy plants.

2 Apply an organic fungicide to protect remaining healthy tissue and control the spread of the mold.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

3 Improve air circulation around the plants and reduce humidity by avoiding overhead watering and ensuring adequate spacing.

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Powdery Mildew

Certain species of powdery mildew produce a white, flour-like coating on the leaves and occasionally parts of the developing curd. It is caused by fungal spores that thrive in environments with high humidity but dry leaf surfaces.

Common

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How to confirm: Observe if the white patches are strictly on the surface of the leaves rather than emerging from within the plant tissue.

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

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 or cauliflower curds to reduce the fungal load in the plant area.

3 Improve air circulation around the plants and avoid overhead watering to keep leaf surfaces dry, as high humidity promotes spore germination.

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Mealybugs

These small insects secrete a white, waxy, cottony substance to protect themselves while feeding on the sap of the cauliflower. Their presence often results in localized yellowing or stunted growth around the infestation site.

Common

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How to confirm: Use a magnifying glass to look for tiny, slow-moving insects underneath the white waxy clusters.

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1 Isolate the cauliflower plant from other vegetables to prevent the mealybugs from spreading to your entire garden.

2 Apply an organic insecticide spray to the affected areas to eliminate the mealybug insects and their protective waxy coating.