How To Kill Azolla Weed Very Well

How To Kill Off Persistent Azolla Weed Very Well

Problem azolla weed controlAzolla, also known as Water Fern or Mosquito Fern, is the fastest growing freshwater plant. The symbiotic association of Azolla with blue, green alga Anabaena provides it with nitrogen, which helps the plant to grow its biomass very fast. Azolla floats on water with its small scale-like leaves and their roots under water. This plant can colonize the freshwater areas at great speed. They are used as bio fertiliser but are considered as a weed as they entirely cover the water bodies. Depending on the exposure of the plant to the sun, the Azolla can appear green or red in colour. The excess growth of the plant can block the water pumps and their filters. Azolla in water bodies can reduce the oxygen content in water. Therefore care should be taken to control the weed, if the Azolla weed is not treated and takes over. Beyond a doubt, it can kill off live fish and frogs spawning eggs masses. Why it is simple, swimming animals cannot survive under water without oxygen.

Preventing Excessive Growth

  • The excessive growth of Azolla plants can be prevented by reducing the amount of nutrients reaching the dams or freshwater areas. Good nutrient content in the water will favour the growth of Azolla.
  • It is necessary to prevent the run off water containing fertilisers and sediments from reaching the water body.
  • Creating buffer strips using shrubs and grass near dams and along drainage will intercept the entry of nutrients and soil particles into the dam.


  • Planting trees on the north and west sides of the water body can minimize the sunlight penetration into the water and can reduce Azolla growth.
  • Prevent the livestock from accessing water and urinating in and defecating in water to reduce the addition of nutrients which promotes Azolla growth.

How to Control Azolla?

It is difficult to completely eradicate aquatic weeds which have a rapid growth rate. The control methods should depend on the extent of the infestation. The Azolla weed control methods include physical removal of the plants, spray treatments or a combination of both methods. When the infestations are smaller, the spray treatments are effective. When the infestation is excess and covers more than 90% of the water surface, you may need to use a physical removal as well as a spray treatment to control the weed.

Spray Treatment for Weed Control

All types of Azolla can be effectively controlled by using “Free Floating Aquatic Weed Control” spray. This spray is easy to apply and is safe to use. It quickly affects only weeds like Azolla, Duckweed, Salvinia etc and not other water plants. The water is safe to consume after treatment as the spray doesn’t have any withholding period. This is not a herbicide and hence safe for other aquatic life, pets, birds etc. This spray affects Azolla by causing shrivelling of the hairs on the leaves. These hairs on the leaf of Azolla help the plant to float by trapping air in between them. Free floating weed control reduces the surface tension of water and reduces the buoyancy of the weeds. This will cause the plants to sink in water and die. It is advisable to give 2 to 3 light applications of the spray within a period of 1 to 3 weeks instead of a single heavy use. In case the weed coverage is more than 90% of the surface area of the water body, it is necessary to remove some of the weeds physically to create space for the weeds to sink after the application of the spray.


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