Chinese Cabbage (Napa) Tiny Black Flies - Causes & Fixes

Jump to cause: Fungus Gnats Black Swallowtail Butterfly Larvae/Adults Leafminers (Agromyza spp.)

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Fungus Gnats

The small black flies are likely adults of the fungus gnat species, which thrive in the moist organic matter often found in Napa cabbage beds. While adults are a nuisance, their larvae feed on decaying plant roots and fungi, potentially causing root damage.

Very Common

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How to confirm: Set a yellow sticky trap near the base of the cabbage to see if small, dark-winged insects are captured.

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

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2 Reduce watering frequency and allow the top inch of soil to dry out to eliminate the moist environment larvae need to survive.

GROWIT Soil Moisture Meter SMM-V3

Water Meters

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3 Apply a biological control or organic insecticide to target the larvae in the soil and protect the root system.

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Black Swallowtail Butterfly Larvae/Adults

Members of the Pieridae family are attracted to brassicas like Napa cabbage for egg-laying. The 'flies' might be small, dark-colored butterflies or moths that have recently emerged and are searching for host plants.

Common

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How to confirm: Inspect the undersides of the large cabbage leaves for small green caterpillars or white clusters of eggs.

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1 Apply an organic insecticide spray to eliminate larvae and deter adult butterflies from laying more eggs on your cabbage.

Bonide Captain Jack's Neem Oil 32 oz

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2 Use yellow sticky traps to capture any flying adults or emerging pests near the cabbage plants.

Super Ninja Fungus Gnat Traps - 30 Pack

30 pcs

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In Stock

3 Inspect the undersides of leaves manually and remove any visible larvae or egg clusters by hand.

warning

Leafminers (Agromyza spp.)

Small flies related to the leafminer species are attracted to the succulent leaves of Napa cabbage. While the adults are tiny and dark, they cause visible 'trails' or serpentine blotches within the leaf tissue as their larvae feed.

Common

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How to confirm: Look for silvery, winding tunnels inside the fleshy leaves of the cabbage head.

build How to fix it

shopping_cart Recommended Products

1 Apply an organic insecticide to eliminate the adult flies and prevent further egg-laying on the cabbage leaves.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

2 Use yellow sticky traps to capture the adult flies and monitor the population levels in your garden.

Super Ninja Fungus Gnat Traps - 30 Pack