Mosquito Fern (Azolla) Identification & Treatment

Scientific Name: Azolla spp. Category: Floating Tier: 3 — Localized — Limited geographic range or lower frequency

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Identification

Mosquito fern is a very small, free-floating fern forming velvety mats on the water surface. Individual plants are about 1/2 to 1 inch across. Color ranges from green to reddish-brown depending on conditions and season. Key distinguishing features:

• Very small, overlapping scale-like leaves
• Velvety surface texture
• Green to reddish-brown color
• Forms dense surface mats

Treatment

• Propeller (flumioxazin) — Contact herbicide. Part of the Duckweed Destroyer pack.
• Harvester (diquat) — Contact herbicide.

Full Profile

• Native Range: Native to the Americas
• US Distribution: Widespread in warmer regions. USDA Zones 5–11.
• Regulatory Status: Not regulated (native).
• Habitat: Still freshwater — ponds, ditches, rice paddies.
• Reproduction: Fragmentation.
• Ecological Benefits: Fixes atmospheric nitrogen (through symbiotic cyanobacteria Anabaena azollae), making it valuable in agriculture. Provides surface cover for aquatic organisms. Generally benign unless excessively dense.

Sources: Texas A&M AquaPlant – Mosquito Fern | USDA PLANTS Database

Related Species

• Duckweed (Lemna minor and related species (L. gibba, L. turionifera, Spirodela polyrhiza)) — Floating, Tier 1
• Watermeal (Wolffia spp. (W. columbiana, W. brasiliensis)) — Floating, Tier 1
• Water Hyacinth (Eichhornia crassipes) — Floating, Tier 1
• Water Lettuce (Pistia stratiotes) — Floating, Tier 2
• Giant Salvinia (Salvinia molesta) — Floating, Tier 2
• European Frog's-bit (Hydrocharis morsus-ranae) — Floating, Tier 3

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