Rieger Begonia White Cottony Spots - Causes & Fixes

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Mealybugs

These small insects secrete a white, waxy substance that looks like cotton to protect themselves. They feed on the sap of Rieger Begonia stems and leaf undersides, causing leaves to yellow or drop.

Very Common

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How to confirm: Inspect the junctions where leaves meet the stem for tiny, moving white insects or sticky residue.

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

2 Treat the infestation by spraying the plant with an organic insecticide/miticide to kill the insects and their waxy coating.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

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3 Use a cotton swab dipped in rubbing alcohol to manually remove visible white cottony clusters from stems and leaf undersides.

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Botrytis Blight (Gray Mold)

High humidity and poor air circulation around the succulent Rieberg Begonia leaves can trigger this fungal pathogen. It often appears as fuzzy, white-to-gray mold patches on decaying plant tissue.

Common

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How to confirm: Check if the white spots are accompanied by soft, brown, water-soaked lesions on the leaf edges.

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1 Prune and remove all infected leaves or plant tissue immediately to prevent the fungus from spreading to healthy parts of the Begonia.

2 Apply an organic fungicide to treat the remaining healthy tissue and suppress the mold growth.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

3 Improve air circulation around the plant and reduce humidity by avoiding overhead watering, ensuring the leaves stay dry.

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Powdery Mildew

This fungal disease manifests as a fine, white powdery coating on the surface of the foliage. It thrives in environments with fluctuating humidity and can cause the Begonia leaves to curl or become distorted.

Common

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How to confirm: Check if the white spots look like a dusting of flour that can be partially wiped off with your finger.

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1 Apply an organic fungicide to the affected leaves to eliminate the powdery mildew fungus and prevent further spread.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

2 Prune and discard any heavily infected leaves to reduce the fungal load on the plant.

3 Improve air circulation around the plant and avoid overhead watering to create a less humid environment for the fungus to thrive.

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Cottony Blight (Sclerotinia)

This soil-borne fungal pathogen can cause white, fuzzy mycelium to appear on the stems or leaf bases of Begonias. It eventually leads to stem rot and total plant collapse.

Common

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How to confirm: Examine the base of the plant for white fungal growth and check if the main stem feels soft or hollow.

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shopping_cart Recommended Products

1 Immediately remove and discard all infected stems and leaves to prevent the fungal mycelium from spreading to healthy tissue.

2 Apply an organic fungicide to the remaining healthy plant tissue to suppress the spread of the blight.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

3 Improve air circulation around the plant and reduce moisture at the base of the stems to create an environment less hospitable to Sclerotinia.

Rieger Begonia – White Cottony Spots

search Possible Causes

Mealybugs

Botrytis Blight (Gray Mold)

Powdery Mildew

Cottony Blight (Sclerotinia)

Other Rieger Begonia problems

Measuring System

Rieger Begonia – White Cottony Spots

search Possible Causes

Mealybugs

Botrytis Blight (Gray Mold)

Powdery Mildew

Cottony Blight (Sclerotinia)

Other Rieger Begonia problems