Calathea loeseneri Tiny Black Flies - Causes & Fixes

Jump to cause: Fungus Gnats Overwatering and Soil Compaction High Organic Matter in Potting Mix

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Fungus Gnats

The tiny black flies are likely the adult stage of fungus gnats, which thrive in the moist, organic-rich soil that Calathea loeseneri requires. Their larvae live in the top layer of soil and feed on decaying organic matter and occasionally fine root hairs.

Very Common

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

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

Super Ninja Fungus Gnat Traps - 30 Pack

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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 Analog Soil Moisture Meter

Water Meters

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3 Apply a microbial-based soil drench to target the larvae living in the organic matter.

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Overwatering and Soil Compaction

Excessive moisture in the Calathea's potting medium creates an ideal breeding ground for fungus gnat larvae. If the soil stays saturated, it also risks causing root rot, which further attracts scavengers to the decaying roots.

Very Common

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How to confirm: Stick your finger two inches into the soil to check if it remains damp for too many consecutive days.

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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

—

2 Repot the Calathea in a fresh, well-aerated potting mix and consider adding perlite to improve drainage and prevent future soil compaction.

3 Apply a biological control like yellow sticky traps to capture adult flies and prevent further breeding.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

$7

In Stock

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High Organic Matter in Potting Mix

Calathea loeseneri often requires peat-based or coco-coir mixes which are highly attractive to fungus gnats for egg-laying. An abundance of decomposing leaf litter or uncomposted mulch on the soil surface provides a perfect nursery for these flies.

Common

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How to confirm: Inspect the soil surface for any visible organic debris or loose bark that could serve as a food source.

build How to fix it

shopping_cart Recommended Products

1 Apply a biological control method to eliminate existing larvae and adults; use yellow sticky traps to capture flying adults.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

$7

In Stock

2 Remove the top layer of decomposing organic matter or mulch from the soil surface to destroy the fungus gnat nursery.

3 Repot the plant in a fresh, well-draining medium and ensure the top layer of soil is clean to prevent re-infestation.