Calathea stromata Tiny Black Flies - Causes & Fixes

Jump to cause: Fungus Gnats (Sciaridae) Overwatering and Root Decay Organic Matter Accumulation

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Fungus Gnats (Sciaridae)

The presence of tiny black flies in a moisture-loving plant like Calathea stromata almost certainly indicates fungus gnats, which lay eggs in the top layer of damp organic matter. Their larvae feed on decaying organic material and can occasionally damage the delicate root hairs of the Calathea.

Very Common

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How to confirm: Set up a yellow sticky trap near the foliage to confirm if small flying insects are being captured.

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1 Deploy yellow sticky traps near the soil surface to capture the adult flying gnats and break the reproductive cycle.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

$7

In Stock

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 drench or supplement to the soil to promote a healthy root zone and compete with gnat larvae.

FoxFarm Bush Doctor Microbe Brew 1 Gallon

3.8 L

$115

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Overwatering and Root Decay

Calathea stromata requires high humidity but is highly susceptible to root rot if the substrate remains saturated. Constant moisture provides the ideal breeding ground for fungus gnat larvae and creates a nutrient-poor, anaerobic environment.

Very Common

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How to confirm: Gently lift the plant from its pot to check if the roots are dark, slimy, or smelling of decay.

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1 Immediately inspect the roots for mushy, dark brown decay and prune away any rot using sterilized shears.

2 Repot the plant in a fresh, well-draining medium like a mix of organic potting soil and perlite to improve aeration and prevent future rot.

3 Deploy yellow sticky traps to capture the adult fungus gnats and reduce the breeding population in the soil.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

$7

In Stock

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Organic Matter Accumulation

Decomposing leaves or old potting media within the Calathea's pot can serve as a food source and breeding site for flies. As these organic components break down, they release gases and nutrients that attract various dipteran species.

Common

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How to confirm: Inspect the surface of the soil for any visible decaying leaf fragments or thick layers of decomposing moss.

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shopping_cart Recommended Products

1 Remove all decaying leaves and debris from the soil surface to eliminate breeding sites for the flies.

2 Repot the Calathea in fresh, well-draining potting soil to replace the old, decomposing organic matter.