Calathea setosa Tiny Black Flies - Causes & Fixes

Jump to cause: Fungus Gnats (Sciaridae) Excessive Soil Moisture Over-fertilization / Organic Decomposition

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Fungus Gnats (Sciaridae)

The tiny black flies are likely fungus gnat adults, which lay eggs in the top layer of moist organic matter. Their larvae live in the soil and feed on decaying organic material and occasionally fine root hairs of the Calathea.

Very Common

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How to confirm: Place a yellow sticky trap near the base of the plant to confirm the presence of flying adults.

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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 biological treatment or ensure the soil surface is covered with a dry medium like perlite to prevent egg laying.

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Excessive Soil Moisture

Calathea setosa requires high humidity but is highly susceptible to root rot from soggy soil. Constant moisture creates the perfect breeding ground for fungus gnat larvae and promotes fungal growth that attracts them.

Very Common

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How to confirm: Stick your finger two inches into the soil; if it feels saturated, reduce watering frequency immediately.

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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 breeding 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 reproduction.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

$7

In Stock

3 Repot the plant in a well-draining medium enriched with perlite to improve aeration and prevent future soil saturation.

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Over-fertilization / Organic Decomposition

Excessive use of organic fertilizers or decomposing peat/bark in the potting mix provides a nutrient-rich environment for flies to breed. As this matter breaks down, it releases CO2 and moisture that attracts adult gnats.

Common

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How to confirm: Check if there is a sour smell coming from the soil or if you have recently added heavy amounts of compost/manure.

build How to fix it

shopping_cart Recommended Products

1 Apply a biological control to eliminate the adult and larval stages of the flies.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

$7

In Stock

2 Reduce watering frequency and allow the top inch of soil to dry out to disrupt the breeding cycle in the moist organic matter.

GROWIT Soil Moisture Meter - Blue