Phaseolus lunatus White Cottony Spots - Causes & Fixes

Jump to cause: Powdery Mildew Mealybugs Cottony Blotch (Sclerotinia)

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Powdery Mildew

This fungal disease is very common in Phaseolus lunatus, especially in high humidity. It presents as white, flour-like patches on leaves that can eventually cause the foliage to yellow and die.

Very Common

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How to confirm: Inspect the underside of the leaves for fine, white mycelium threads.

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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 dispose of any heavily infected leaves to reduce the fungal load in the plant canopy.

3 Improve air circulation around the plant and reduce humidity to create an environment less favorable for mildew growth.

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Mealybugs

These small insects secrete a waxy, white substance to protect themselves, which looks like tiny tufts of cotton on stems and leaf axils. They suck sap from the lima bean plant, weakening it significantly.

Common

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How to confirm: Look for tiny, slow-moving insects nestled within the white spots during close inspection.

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1 Isolate the plant immediately to prevent the mealybugs from spreading to other greenery and use a cotton swab dipped in isopropyl alcohol to manually remove visible white clusters.

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

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

3 Monitor the soil moisture levels to ensure the plant is not overly wet, as high humidity can encourage pest populations.

GROWIT Soil Moisture Meter - Blue

Water Meters

$12

In Stock

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Cottony Blotch (Sclerotinia)

This soil-borne pathogen can cause white, fuzzy mycelium to appear on stems or near the base of the lima bean plant. It often leads to rapid stem decay and wilting.

Common

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

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shopping_cart Recommended Products

1 Immediately remove and destroy any infected plant material or stems showing white fuzzy growth to prevent the pathogen from spreading to healthy plants.

2 Apply a fungicide to protect remaining healthy tissue and improve air circulation around the base of the plant to reduce moisture.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

3 Ensure the soil is not overly saturated by using a moisture meter to monitor levels and avoid overwatering, which promotes Sclerotinia growth.

GROWIT Soil Moisture Meter - Blue

Water Meters

$12

In Stock