8.3 Category 05: Aquatic & Category 07: Right-of-Way Pest Control

8.3 Category 05: Aquatic & Category 07: Right-of-Way Pest Control

[!NOTE] Jurisdictional Scope: Commercial Category 05 (Aquatic Pest Control) authorizes pesticide applications applied deliberately to standing or running water, ponds, lakes, reservoirs, irrigation canals, drainage ditches, retention basins, and wetland margins. Sub-category 05S specializes in sewer root eradication. Commercial Category 07 (Right-of-Way Pest Control) governs chemical vegetation management along public roadways, highway medians, railroad rights-of-way, electric utility corridors, petroleum pipelines, substations, and industrial tank farms. Both categories demand strict environmental stewardship to safeguard Nebraska's surface waters and non-target ecosystems.

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Category 05: Aquatic Pest Control Scope & Label Restrictions

Applying pesticides directly to aquatic environments presents immediate exposure risks to non-target fish, aquatic macroinvertebrates, waterfowl, livestock, and downstream domestic water supplies. Only products carrying explicit EPA-approved aquatic use registrations may be introduced into water bodies.

Critical Water-Use Restrictions

Aquatic herbicide labels prescribe mandatory water-use setback intervals following treatment. Certified applicators must identify and comply with restrictions governing:

• Drinking Water (Potable Use): Setback distances from municipal or domestic water intakes, ranging from zero up to 14 days or requiring residue testing below established parts-per-billion (ppb) thresholds.
• Livestock Watering: Mandatory waiting intervals (often 1 to 14 days) before livestock may drink treated pond water.
• Crop Irrigation: Strict prohibitions on using treated water to irrigate sensitive agricultural crops, turf, or greenhouse ornamentals (e.g., water treated with 2,4-D, triclopyr, or fluridone can cause severe crop phytotoxicity if applied via overhead pivots).
• Swimming & Recreation: Intervals (typically 24 hours) during which swimming and whole-body water contact are restricted.
• Fish Consumption: Waiting periods before human consumption of fish harvested from treated waters.

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Classification of Aquatic Weeds and Algae

Selecting the correct chemical and application methodology requires diagnosing the target organism's morphological growth habit.

+-------------------------------------------------------------------------+
|                   AQUATIC VEGETATION CLASSIFICATIONS                    |
| 1. Submerged: Grow entirely beneath water surface (milfoil, pondweeds)  |
| 2. Floating: Float on surface, free or rooted (duckweed, watermeal)     |
| 3. Emergent: Rooted in submersed soil with aerial shoots (cattails)     |
| 4. Algae: Non-vascular photosynthetic plants (planktonic, filamentous)  |
+-------------------------------------------------------------------------+

1. Submerged Aquatic Plants

Submerged plants grow entirely underwater, rooted in bottom sediment (though fragments may float).

• Sago Pondweed (Stuckenia pectinata): Slender, thread-like leaves branching fan-like; produces nutritious starchy tubers for waterfowl.
• Curlyleaf Pondweed (Potamogeton crispus): Invasive perennial with wavy, crinkled leaf margins resembling lasagna noodles. Unique lifecycle: germinates in autumn, grows actively under ice, produces vegetative reproductive buds (turions) in late spring, and naturally senesces in early summer, triggering sudden nutrient releases.
• Coontail (Ceratophyllum demersum): Rootless, free-floating submerged plant with stiff, whorled leaves resembling a raccoon's tail.
• Eurasian Watermilfoil (Myriophyllum spicatum): Aggressive, exotic submerged invasive featuring delicate, feathery leaves arranged in whorls of 4 (with 12 to 21 pairs of thread-like leaflets per leaf). Forms dense surface canopies that choke boat traffic and outcompete native macrophytes; spreads primarily through vegetative auto-fragmentation.

2. Floating Aquatic Plants

Floating plants reside on the water surface and are either free-floating or rooted in bottom sediment with floating leaves.

• Duckweed (Lemna minor): Minute, free-floating flowering plant with oval fronds (1/8 to 1/4 inch) possessing a single root dangling beneath each frond.
• Watermeal (Wolffia columbiana): The smallest flowering plant on Earth. Rootless, granular green specks resembling floating grains of cornmeal or sand. Extremely difficult to control; physical contact feels gritty between fingers.
• White Waterlily (Nymphaea odorata): Rooted in bottom muck with large, circular floating leaves featuring a deep V-shaped cleft.

3. Emergent Aquatic Plants

Emergent plants are rooted in saturated shoreline sediments with stems, foliage, and flowers extending upright above the water surface.

• Broadleaf Cattail (Typha latifolia): Tall, erect marsh perennial (5 to 10 feet) with flat sword-like leaves and cylindrical brown flower spikes. Dense stands impede water flow and accelerate siltation.
• Bulrushes (Schoenoplectus spp.): Triangular or cylindrical unbranched stems growing in shallow marshes and lakeshores.
• Common Reed / Phragmites (Phragmites australis): Robust, aggressive invasive perennial grass growing 10 to 15 feet tall with dense, purplish-brown feathery seed plumes. Chokes Nebraska river sandbars and irrigation ditches.

4. Algae Classifications

Algae are primitive non-vascular photosynthetic organisms lacking true roots, stems, or leaves:

• Planktonic Algae: Microscopic single-celled or colonial organisms suspended in the water column. Excessive nutrient loading (phosphorus/nitrogen) generates dense blooms that color water pea-soup green or brownish. Cyanobacteria (blue-green algae, such as Microcystis and Anabaena) produce dangerous hepatotoxins and neurotoxins (Harmful Algal Blooms, HABs) that sicken or kill livestock and pets.
• Filamentous Algae: Hair-like cell chains that grow on underwater substrate and detach to form unsightly, floating yellowish-green mats ("moss" or "pond scum," such as Spirogyra or Cladophora).
• Macrophytic Algae / Chara (Chara spp., Muskgrass / Stonewort): An advanced multicellular branching alga that grows attached to pond bottoms, heavily resembling a rooted higher vascular plant. It is heavily encrusted with calcium carbonate deposits, giving it a rough, gritty texture, and emits a powerful, pungent skunky or garlic-like odor when crushed between fingers.

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Water Treatment Mathematics: Surface Acres, Acre-Feet & The 2.7 Constant

Applying pesticides to water bodies requires volumetric dosing calculations. Unlike terrestrial spraying where output is calibrated per surface acre, aquatic treatments are dosed on a parts-per-million (PPM) concentration within a three-dimensional volume of water.

1. Determining Surface Area (Acres)

• Rectangular or Square Water Body: $\text{Surface Acres} = \frac{\text{Length (feet)} \times \text{Width (feet)}}{43,560\text{ sq ft per acre}}$
• Circular Water Body: $\text{Surface Acres} = \frac{3.14 \times \text{Radius (feet)}^2}{43,560}$

2. Calculating Water Volume: Acre-Feet

An Acre-Foot represents the volume of water required to cover exactly one surface acre to a uniform depth of one foot. $\text{Acre-Feet} = \text{Surface Acres} \times \text{Average Depth (feet)}$ Determining Average Depth: The applicator must conduct systematic depth soundings along grid transects across the water body using a calibrated weighted line or electronic sonar depth-finder, summing the readings and dividing by the total number of soundings.

3. The 2.7 Constant Derivation & Dosage Formula

To determine the exact quantity of pesticide active ingredient required to achieve a targeted parts-per-million (PPM) concentration, applicators rely on the universal constant 2.7:

• 1 acre-foot contains $43,560\text{ cu ft}$.
• 1 cubic foot of water contains $7.48\text{ gallons}$.
• Therefore: $43,560 \times 7.48 = 325,851\text{ gallons of water per acre-foot}$.
• Water weighs $8.34\text{ pounds per gallon}$.
• Total weight of 1 acre-foot of water: $325,851 \times 8.34 = 2,717,597\text{ pounds}$ (approximately 2.72 million pounds).
• A concentration of 1 PPM equals 1 pound of active chemical ingredient per 1 million pounds of water.
• To achieve 1 PPM in 2.72 million pounds of water requires: 2.72 pounds (rounded to 2.7 pounds of active ingredient).

+-------------------------------------------------------------------------+
|                   UNIVERSAL AQUATIC DOSAGE FORMULA                      |
| Pounds of Active Ingredient = Acre-Feet × Desired PPM × 2.7             |
|                                                                         |
| For dry formulations:                                                   |
| Pounds of Product = (Acre-Feet × Desired PPM × 2.7) / (% A.I. / 100)    |
|                                                                         |
| For liquid formulations:                                                |
| Gallons of Product = (Acre-Feet × Desired PPM × 2.7) / (Lbs A.I. / gal) |
+-------------------------------------------------------------------------+

Worked Calculation Example

Problem: An applicator must treat a 3-acre irrigation pond with an average depth of 4 feet to control submerged pondweeds using a 100% active copper sulfate pentahydrate product at a label-prescribed rate of 1.5 PPM.

1. Calculate Acre-Feet: $3.0\text{ surface acres} \times 4.0\text{ feet} = 12.0\text{ Acre-Feet}$.
2. Apply the dosage formula: $\text{Pounds of Product} = 12.0\text{ Acre-Feet} \times 1.5\text{ PPM} \times 2.7 = 48.6\text{ pounds}$ Result: The applicator must dispense exactly 48.6 pounds of copper sulfate.

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Dissolved Oxygen Depletion & The Sectional Treatment Rule

The most catastrophic error an aquatic applicator can commit is treating an entire water body choked with dense vegetation during hot weather, causing a massive fish kill.

The Mechanism of Fish Suffocation

Pesticides like copper complexes or diquat kill aquatic weeds and algae rapidly. As target plants die, their biomass collapses and sinks to the bottom sediment. Aerobic decomposer bacteria multiply exponentially to consume the decaying organic matter. During this decomposition process, bacteria consume massive volumes of dissolved oxygen (DO) from the water column.

• The Temperature Impact: Warm water has a substantially lower oxygen-holding capacity than cold water. In summer, water temperatures frequently exceed 75°F to 80°F, meaning baseline dissolved oxygen levels are already naturally depressed.
• The Consequence: If large biomass dies simultaneously, microbial biological oxygen demand (BOD) drives dissolved oxygen down to lethal levels (<2 to 3 mg/L). Fish do not die from chemical pesticide toxicity; they die from acute oxygen suffocation.

The 1/3 to 1/2 Sectional Treatment Rule

To prevent dissolved oxygen crashes in water bodies with moderate to heavy plant growth during warm weather (water temperatures >70°F):

1. Treat only one-third (1/3) to one-half (1/2) of the water body surface area in a single application.
2. Leave untreated areas adjacent to treated zones, allowing fish a safe oxygenated refuge zone.
3. Wait 10 to 14 days between sectional treatments. This waiting window allows bacteria to complete decomposition of the initial vegetation batch and permits dissolved oxygen levels to rebound before the next section is treated.

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Aquatic Herbicide Chemistries & Sub-Category 05S (Sewer Root Control)

• Copper Compounds (Copper Sulfate & Chelated Coppers): Primary contact algaecides. Chelated coppers (e.g., Cutrine-Plus) hold copper ions in organic complexes, preventing precipitation in hard, alkaline Nebraska waters and extending contact activity.
• Diquat Dibromide: Fast-acting contact bipyridylium herbicide. Highly effective on duckweed, watermilfoil, and pondweeds. Critical restriction: Diquat binds tightly and irreversibly to suspended clay, silt, and soil particles. Applying diquat to muddy, turbid water renders the herbicide completely inactive.
• Endothall: Contact herbicide. Available in two formulations: dipotassium salt (Aquathol), which is safe for fish, and alkylamine salt (Hydrothol), which is an effective algaecide and herbicide but is highly toxic to fish at rates exceeding 0.3 PPM.
• Fluridone (Sonar): Systemic carotenoid inhibitor (bleaching herbicide). Requires an extended contact time (30 to 90 days) at parts-per-billion (ppb) concentrations. Exceptional for selective whole-lake management of Eurasian watermilfoil and duckweed.
• Glyphosate & Triclopyr (Aquatic Labels): Systemic herbicides applied to aerial foliage of emergent plants (cattails, phragmites). Applicators must use registered aquatic formulations (e.g., Rodeo) and mix with an approved aquatic-labeled non-ionic surfactant. Standard terrestrial Roundup formulations contain POEA (polyethoxylated tallow amine) surfactants that damage fish gill membranes and are strictly illegal in aquatic sites.
• Sub-Category 05S: Sewer Root Control: Specialized sub-category involving the introduction of metam sodium and dichlobenil injected under pressure as a dense, long-lasting chemical foam inside municipal and commercial sanitary sewer mains. The foam fills the entire pipe cross-section, killing intruding tree root tips through contact fumigation and preventing pipe collapse without injuring parent surface trees.

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Category 07: Right-of-Way Pest Control & Brush Eradication

Right-of-way pest management encompasses transport and utility corridors where vegetation obstructs visibility, creates fire hazards, damages track beds, or impairs utility transmission.

Brush Management Application Techniques

1. Foliar Spraying: Broadcast boom spraying or high-volume handgun applications applied to actively growing woody brush foliage during early summer. High risk of off-target drift if applied during windy conditions or onto tall brush.
2. Basal Bark Treatment: Selective woody plant control technique for brush and saplings with stem diameters under 4 to 6 inches. An oil-soluble systemic herbicide (such as triclopyr ester) is mixed in a penetrating oil, mineral oil, or diesel fuel carrier. The mixture is sprayed around the entire circumference of the lower 12 to 18 inches of the stem, thoroughly wetting the bark down to the root collar until runoff occurs. The oil carrier penetrates the suberin layer of the bark, delivering the systemic herbicide directly to the vascular cambium. Basal bark treatments can be applied year-round (including dormant winter months), provided snow or ice does not prevent coverage of the root collar.
3. Cut Stump Treatment: Applied to trees and shrubs immediately after mechanical felling to prevent stump resprouting. Concentrated systemic herbicide (triclopyr amine/ester, glyphosate, or picloram) is brushed or sprayed onto the cut surface within 5 to 15 minutes of cutting. On large stumps (>3 inches diameter), the applicator needs only to thoroughly wet the outer cambium and sapwood ring, as inner heartwood is dead structural tissue.
4. Bare-Ground (Total Vegetation Control): Application of non-selective, long-residual soil sterilants (e.g., imazapyr, bromacil, tebuthiuron, indaziflam) across gravel electrical substations, railroad ballast, and tank farms. Extreme caution is required: residual sterilants have high mobility (low Koc) and can leach into shallow aquifers or move laterally with surface runoff into roots of non-target trees bordering the site.

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Nebraska Declared Noxious Weeds & Enforcement Mandates

Under the Nebraska Noxious Weed Control Act (Neb. Rev. Stat. §§ 2-945.01 through 2-966), landowners, right-of-way managers, and public agencies have a mandatory legal duty to control and eradicate declared noxious weeds on property under their jurisdiction. The Nebraska Department of Agriculture and local County Weed Control Authorities enforce compliance, possessing statutory authority to issue control notices, perform custom eradication, and place tax liens on non-compliant land.

Priority Nebraska State Declared Noxious Weeds

• Musk Thistle (Carduus nutans): Aggressive biennial. Spiny-winged stems with large, solitary, nodding reddish-purple flower heads surrounded by broad, spine-tipped reflexed bracts. Best controlled in the rosette stage during spring or autumn using 2,4-D, dicamba, or aminopyralid. Once stems bolt and flower, chemical control efficacy drops precipitously.
• Plumeless Thistle (Carduus acanthoides): Biennial resembling musk thistle, but with smaller flower clusters and spiny stem wings running continuously right up to the base of the flower heads.
• Canada Thistle (Cirsium arvense): Creeping dioecious perennial propagating via extensive horizontal lateral roots and airborne seed. Flowers are small (1/2 inch) and spineless, ranging from purple to white. Foliar applications of clopyralid or aminopyralid are most effective when applied at the bud stage in summer or to low rosettes in autumn.
• Spotted Knapweed (Centaurea stoebe): Biennial or short-lived perennial with slender, branched stems and pinkish-purple flowers. Involucre bracts have distinct dark, comb-like tips resembling black spots. Excretes allelopathic toxins into soil.
• Saltcedar (Tamarix ramosissima): Invasive, shrubby deciduous tree infesting riverbanks and wetlands across the Platte, Republican, and Niobrara River basins. Deep taproots consume massive quantities of groundwater; foliage secretes salt, salinizing soil surface. Controlled via aerial imazapyr, basal bark triclopyr, or cut stump applications.
• Phragmites / Common Reed (Phragmites australis): Aggressive invasive grass choking Nebraska river braided channels and drainage canals. Dense stands exclude wildlife and exacerbate flooding. Managed via late-summer or early-fall aerial or ground foliar applications of aquatic glyphosate or imazapyr.