Watermeal is a very tiny (less than 1 millimeter) light green free-floating, rootless plant.
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Watermeal (Wolffia spp)


Watermeal is a very tiny (less than 1 millimeter) light green free-floating, rootless plant. In fact, watermeals are the smallest seed-bearing plants in the world. Watermeal tend to grow in dense colonies in quiet water, undisturbed by wave action. Often watermeal will be associated with colonies of duckweeds. Watermeal can be an aggressive invader of ponds and are often found mixed in with duckweeds or mosquito fern. If colonies cover the surface of the water, then oxygen depletions and fish kills can occur. These plants should be controlled before they cover the entire surface of the pond.

Dense colonies of watermeal often can completely cover the surface of a pond and will cause dissolved oxygen depletions and fish kills These colonies will also eliminate submerged plants by blocking sunlight penetration. Watermeal is not known as an important food but many ducks may consume it and often transport it to other bodies of water.

Watermeal Control Options


Watermeal can be removed by ranking or seining it from the pond's surface but it is so small it is very difficult to physically removed.


Tilapia will consume watermeal but are a warm water species that cannot survive in temperatures below 55° F. Therefore, tilapia usually cannot be stocked before mid-April or May and will die in November or December. Recommended stocking rates are 15 to 20 pounds of mixed sex adult Mozambique tilapia (Oreochromis mossambicus) per surface area. Tilapias are often not effective for vegetation control if the pond has a robust bass population due to intense predation.


The active ingredients that have been successful in treating duckweeds include fluridone (E). E = excellent, G = good

p>Resources: Department of Wildlife and Fisheries Sciences, Texas A&M University

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Products to Control Watermeal

Planktonic Algae

WhiteCap is a fluridone compound and has been effective on coontail. It is a broad spectrum, systemic herbicide. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides.

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