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

Handle herbicides safelyAlthough aquatic herbicides arerelatively safe to handle, it isnevertheless important for applicators tokeep chemical exposure to an absoluteminimum. Herbicide labels and materialsafety data sheets advise what protectiveclothing and equipment should be worn,any precautions the handler shouldfollow, a statement of practical treatmentin case of poisoning, statementsconcerning hazards to the environment,any physical or chemical hazards, anddirections on proper storage anddisposal. By law, copies of labels andany supplementary labels must be in thepossession of the applicator at theapplication site for each herbicide used.Anyone who handles a pesticide mustread and understand all label statementsprior to using the product. Herbicidesafety is reviewed in SRAC publication3601 which can be found atwww.msstate.edu/dept/srac .Dispose of herbicide containersproperlyImproper disposal of herbicidecontainers can cause contamination ofsoil and water, and may result in fines orloss of an applicator’s license. Emptyherbicide containers must be triplerinsed, with each rinsing drained into theherbicide mix tank. If no mix tank isused, the rinse water from the containershould be applied to the pond in thesame manner as the herbicide in thecontainer. Containers must then bepunctured or crushed so that they can notbe reused. Empty bags must be rinsed orshaken clean and cut so that they can notbe used for other purposes. Lawsregarding disposal of rinsed containersvary among states, so be sure to followall state and local regulations regardingpesticide container disposal.Two aquatic herbicides, 2,4-Dand endothall, are regulated as hazardousmaterials under federal law, and anywaste generated during their use must bedisposed of as hazardous waste. Triplerinsedcontainers can be disposed of aswith any other pesticide container. Anyrinse water from cleaning of containersor application equipment must beapplied as if it were the herbicide ordisposed of at a hazardous wastedisposal facility.Consequences of herbicide useWhen used according to themanufacturer’s specifications, herbicidesare seldom directly toxic to fish.However, the addition of any herbicideto a plant-infested body of water willalter water quality. Oxygen productionby photosynthesis will be decreased anddecomposition of the dead plant materialwill increase oxygen consumption. Theresult will be a noticeable decrease indissolved oxygen concentrationscompared to pretreatment levels. Theextent to which dissolved oxygen levelsare reduced depends on the amount ofplant material killed, the amount of plantmaterial unaffected by the herbicide, therate that death occurs, water temperatureand other factors. Decomposition of thedead plants will also raise carbondioxide and total ammoniaconcentrations. The increase in totalammonia concentrations tends todecrease the pH, causing much of theammonia to be in the non-toxic, ionizedform. Phosphorus, potassium, and otherminerals are also released upon plantdecomposition, and concentrations of allessential plant nutrients will usually behigher after herbicide treatment. Atsome time after treatment, theconcentration of herbicide will decrease18