Aquatic Weed Control in Ponds - Aquaculture at Kentucky State ...

form, but the liquid is most commonlyused. The copper in these herbicides isbound in organic complexes so that thecopper will not precipitate out ofsolution as rapidly as uncomplexedcopper in hard, alkaline waters. Cutrine-Plus, for example, has a prolongedeffectiveness because its chelating agent,ethanolamine, decomposes slowly insunlight. Although chelated copperherbicides usually are more effectivethan copper sulfate, they areconsiderably more expensive to use.The table on page 21 of this booklet liststhe aquatic weeds controlled by each ofthe chelated copper compounds. Copperherbicides have a reputation foreffectively killing algae includingphytoplankton, some filamentous algaeand Chara (musk grass) which is also analgae. However, Cutrine-Ultra isspecially designed to kill Pithophorawith a penetrating surfactant. AndKomeen, Pondmaster, Nautique, andCaptain, unlike many other chelatedcoppers, are able to control higheraquatic plants like Najas, coontail,Elodea and sago pondweed.Additionally, chelated coppersare often combined with other herbicidessuch as Reward, Aquathol, or Sonar toenhance their effectiveness, and in somecases, reduce the amount needed of bothherbicides.Diquat (Reward, Weedtrine D).Diquat is sold as a liquid containing 2pounds active ingredient per gallon. It isa wide-spectrum herbicide and willcontrol most filamentous algae includingPithophora spp. and Chara spp.,submersed weeds such as Najas spp. andcoontail, and can be mixed with asurfactant and sprayed to controlemergent weeds such as cattail. Diquatshould not be used in muddy water andmud should not be stirred up duringapplication because diquat will bindtightly with clay particles suspended inthe water rendering the herbicideineffective at controlling plants growingbeneath the surface. Diquat should beapplied on a sunny day to activelygrowing weeds. Only 1 / 3 to 1 / 2 of thepond water area should be treated at onetime with a 14-day interval betweentreatments. A 14-day withdrawal periodis required by law after diquat use beforetreated water can be used for animalconsumption, swimming, spraying,irrigation or drinking.Endothall, dipotassium salt(Aquathol, Aquathol K, AquatholSuper K). The dipotassium salt ofendothall is available in liquid (AquatholK) or granular (Aquathol) form. It willnot kill algae but will control a widevariety of submersed higher plants,including Najas spp., coontail, andfanwort. The granular formulation isrelatively expensive, but is particularlyeffective on Najas spp. Dipotassium saltof endothall is a contact killer. It issprayed onto or injected below the watersurface and can be sprayed at highconcentrations directly on exposedweeds. For best results, watertemperatures should be 65º F or above.When water temperatures are high andan increased danger of dissolved oxygendepletion exists, this herbicide should beapplied to 1 / 3 to 1 / 2 of the pond pertreatment with a 5 to 7 day intervalbetween treatment applications.Water treated with granularAquathol must not be used for irrigationor for agricultural sprays on food cropsor for domestic purposes within 7 daysof treatment. More detailed restrictionsexist for Aquathol K. It may not be usedfor the above mentioned purposes aswell as for watering livestock for 7 daysafter applying it up to 0.5 ppm; for 1414