COPPER herbicide supplemental information
Copper is quite toxic to non-target organisms, particularly in soft waters. Only the amine formulation of endothall rivals non-chelated copper formulations in toxicity (EPA, 1985). Copper is considered to be highly toxic to mollusk and fish at relatively low doses. Levels of 1-5 ppm are toxic to fish; however, copper is usually applied at concentrations 1 ppm or less.

DIQUAT herbicide supplemental information
Diquat alone does not provide effective control of hydrilla; however when mixed with chelated coppers, at a rate of two gallons of diquat and four gallons of chelated copper per surface acre, effective, albeit temporary, control of hydrilla is provided. A synergism has been reported between these two compounds such that hydrilla takes up more diquat and copper when they are applied together than when equal concentrations of these compounds are applied separately. Diquat quickly "disappears" from the water column. This disappearance is largely attributed to adsorption to suspended particulate matter, sediments and aquatic plants as well as uptake by aquatic plants. Diquat is not toxic to fish at rates well above those used for weed control. Diquat and copper are not often considered for large scale hydrilla control because repetitive treatments are labor intensive with a high cumulative cost. Repeated annual treatments also require an increased amount of copper to be introduced into the system.

ENDOTHALL herbicide supplemental information
Endothall was first used in agriculture as a plant desiccant. This active ingredient is comprised of only carbon, hydrogen and oxygen. The inorganic salt, normally used at rates of 2-3 ppm in water, is not toxic to adult fish, eggs or fry at rates of 100-800 ppm depending on fish species. The amine salt is 2-3 times more active on plants, but 200-400 times more toxic to fish than the inorganic salt. The amine salt is toxic to fish at 0.5 ppm and carries and EPA label warning not to use it where fish are an important resource. Therefore, the amine salt is not used by itself for large scale hydrilla control. Because of labor and material cost considerations, the inorganic salt of endothatll is used to open trails and "holes" in hydrilla mats. In large systems, such as Lake Tsala Apopka, these trail networks can become extensive and qualify as large scale control projects.

FLURIDONE herbicide supplemental information
Fluridone was first registered for use in agriculture as an herbicide against weeds in cotton fields. It is a systemic herbicide which is absorbed through the the roots and shoots and is translocated to shoot tissues. Fluridone inhibits the synthesis of carotenoid pigments. When this happens, the plants' shoot tips become bleached, turning pink or white, resulting in gradual plant death. Fluridone controls a broad specturm of aquatic plants, but can be somewhat selectively used based on timing of application. Late winter or early spring fluridone treatments seem to provide the best selectivity for hydrilla control, as hydrilla begins robust growth while most non-target native plants are still dormant.

Fluridone has a half-life in water of approximately 20 days; much longer but highly variable in sediments. This herbicide does not accumulate in fish or zooplankton and does not affect algae. It has a low toxicity to fish with about a 100X safety factor at typical treatment rates between 12 and 15 parts per billion.

Two benefits of treating hydrilla with fluridone are the amounts and duration of hydrilla control which are possible from one application. Large scale treatments have provided up to five acres of control for each acre treated for as long as two growing seasons. While initial treatment costs are as high as $750 per acre treated, the costs per acre of hydrilla controlled over a two year period are often less than $100.

Because it requires a long contact time for optimum efficacy, fluridone's cost effectiveness decreases in fast-flowing waters where larger amounts are required to compensate for dilution. Because fluridone disperses so readily throughout waterbodies, spot or partial treatments also are difficult due to dilution.

GLYPHOSATE herbicide supplemental information
Glphosate is a systemic herbicide that moves through the plant from the point of foliage contact to and into the root system. Therefore, it is most effective when applied to actively growing plants which have not been mown, grazed or otherwise disturbed. Visible effects on most annual weeds occur within 2 to 4 days, 7 days or more on most perennial weeks, and 30 days or more on most woody plants and trees. Heavy rainfall or irrigation within 2 hours of application may wash away the herbicide, requiring a repeat treatment; rainfall or irrigation within 6 hours of application may reduce effectiveness.

2,4-D herbicide supplemental information
2,4-D is a plant hormone and plant growth regulator that is used in plant culture. It was discovered in the 1940s. However, at higher rates, it also is used as a herbicide for the control of weeds in food crops, as well as in turf, non-crop areas and in aquatic situations. The invasive aquatic weeds it especially controls are Eurasian water milfoil and water hyacinth.

2,4-D is absorbed by roots and leaves. It translocates to and accumulates mainly in the growing points of shoots and roots. Death of susceptible weeds occurs slowly, usually within 3-5 weeks. On the other hand, at low rates, as a plant growth regulator, 2,4-D can induce rooting and blossom set; 2,4-D is commonly used in plant tissue culture.

2,4-Dichlorophenoxyacetic acid, unfortunately, has sometimes been confused with "Agent Orange", the military's name for a defoliant mixture that was created and used during the Viet Nam war. It turns out that during the manufacture of Agent Orange it became contaminated with a certain cancer-causing dioxin known as TCDD. While 2,4-D was one of the components of Agent Orange, it is not by itself Agent Orange, nor does 2,4-D contain TCDD, nor has 2,4-D been shown to be cancer-causing. After numerous recent lifetime feeding studies in rats and mice, the EPA has classed 2,4-D in Class D - Not Classifiable as to Human Carcinogenicity.

TRICLOPYR herbicide supplemental information
Triclopyr was first reported in 1975. It is applied by spraying the leaves. This herbicide is mainly used in noncrop land areas such as utility and pipeline rights-of-way, roadsides, railroads, rangeland and permanent pastures. It is also applied in turf and in rice. Injected into stem cuts or applied to freshly cut stumps, it controls large trees. It also controls many annual broadleaf weeds. Death of plants treated with triclopyr occurs slowly, usually within 3-5 weeks.

The triclopyr formulation, Renovate, is specifically labelled for use in and around standing water sites, such as marshes, wetlands and the banks of ponds and lakes.

IMAZAPYR herbicide supplemental information
This herbicidal active ingredient was discovered in the 1970s; it was first sold in 1984. Imazapyr is used in noncropland areas, as well as in certain crops, such as sugarcane, rubber and oil palm. It controls grasses, broadleaf plants, vines, brambles, brush and trees. (However, certain pine species are tolerant of this herbicide.) Injury symptoms usually do not appear for 1-2 weeks and more.. At low rates, it acts as a growth regulator, causing certain turf species to grow.

In Florida, it is allowed for use under an Experimental Use Permit, for the control of the very-difficult-to-control, non-native, invasive melaleuca trees and torpedograss.