A website from UGA Cooperative Extension

News, events, and happenings in Colquitt County agriculture.

I respond to all sorts of pond weed calls each week. Several of these calls have been the result of an unusual looking weed called Waterfern (Salvinia minima). Not to be confused with its larger cousin, Giant Salvinia (Salvinia molesta), who is actually on the federal noxious weed list.

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Waterfern is a floating fern that is native to South America. It was probably introduced into the US through the trading of ornamental plants for fish tanks. It grows well in our area and can easily cover the surface of small and medium sized ponds with a dense floating mat if not controlled.

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Herbicides are the most effective control once the weed is established. Be sure not to treat more that 30-40% of the pond area at any one time as decaying plant material will deplete dissolved oxygen and result in fish kills, especially in the warmer months. Only two herbicide active ingredients are particularly effective in controlling this weed:

1) diquat (Reward, many generics)

2) flumioxazin (sold for aquatic use as Clipper)

Both products will require the addition of an aquatic approved spreader/sticker to work properly. Diquat provides descent control of many aquatic weed species. Flumioxazin provides great control of a few common pond weeds. Herbicide choice would depend on other weed species present and size of the area to be treated since flumioxazin is very expensive. Call me for recommendations that fit your specific situation.

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