Begonia havana Rose 865 Tiny Black Flies - Causes & Fixes

Jump to cause: Fungus Gnats Overwatering and Soil Moisture Retention High Organic Matter/Decaying Roots

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Fungus Gnats

The tiny black flies are likely the adult stage of fungus gnats, which thrive in the moist organic matter found in Begonia potting soil. Their larvae feed on decaying organic material and can damage the delicate root systems of your Havana Rose Begonia.

Very Common

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How to confirm: Place a yellow sticky trap near the plant to see if small flying insects are captured.

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1 Deploy yellow sticky traps to capture the adult flying gnats and break the breeding cycle.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

$7

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2 Allow the top inch of soil to dry out completely between waterings to make the environment less hospitable for larvae.

GROWIT Soil Moisture Meter - Blue

Water Meters

$12

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3 Apply a microbial-based treatment or ensure the soil is well-aerated with perlite to prevent the organic decay that larvae feed on.

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Overwatering and Soil Moisture Retention

Begonias prefer consistent moisture but are highly susceptible to root rot if left in saturated soil. High humidity and damp topsoil create the perfect breeding ground for fungus gnat larvae.

Very Common

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How to confirm: Stick your finger two inches into the soil; if it feels muddy or stays wet for many days, you are overwatering.

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1 Reduce watering frequency and allow the top inch of soil to dry out completely before watering again to disrupt the fungus gnat life cycle.

GROWIT Soil Moisture Meter SMM-V3

Water Meters

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2 Apply yellow sticky traps near the soil surface to capture adult flies and prevent further breeding.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

$7

In Stock

3 Repot the plant in a well-draining medium amended with perlite to improve aeration and prevent soil from staying too saturated.

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High Organic Matter/Decaying Roots

If the Havana Rose Begonia has accumulated dead leaf matter on the soil surface or is experiencing early root decay, it provides a food source for flies. This cycle of decay attracts more pests to the plant.

Common

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How to confirm: Gently remove the top layer of soil/mulch and check if there is any visible mold or slimy, dark plant tissue.

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1 Remove all decaying organic matter and dead leaves from the soil surface to eliminate the breeding ground for the flies.

2 Inspect the roots for rot and repot the plant in fresh, well-draining medium like Espoma Organic Potting Soil Mix to prevent further decay.