Preliminary Considerations: It is worth repeating, at this point, that before applying the chemical(s)
the following items should have been covered:
- The nuisance plant(s) correctly identified.
- The area(s) to be treated accurately measured.
- Necessary permits or approvals obtained.
- The proper chemical(s) chosen, dosage rate(s) determined, and the label(s) carefully read.
- Application equipment chosen and in proper working order.
Re-examine the area prior to treatment. If necessary, for reference, mark off the boundaries with floats or flags.
Test run equipment to check for proper operation. If unfamiliar with the use of a liquid sprayer, try a "dry run"
using just water. Note the approximate output rate and spray distance.
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For backpack and power sprayers equipped with tanks, estimate how much surface area can be covered with 1 tankful
of spray solution. The amount of solution placed in the tank should not exceed the amount required for that area.
For example, if a small backpack sprayer has a maximum capacity of 2½ gallons (10 quarts), a 9:1 dilution rate
would be 9 quarts water to 1-quart chemical. If the dosage rate for that chemical is 2 gallons (8 quarts) per
acre, it would take 8 tankfuls of the 9:1 dilution to cover the 1 acre area (8 tankfuls X 1 quart per tankful = 8 quarts
of chemical). Refer to the Dilution/Dosage Rate Chart on page 113 of the Appendix for specific examples.
For pump systems which use lake or pond water for dilution (the AB Aquatic Chemical Sprayer), pump output should be
estimated. To calibrate, place the chemical intake line into a pre-measured volume of water. Adjust the valve to a
standard rate of uptake such as 1 gallon per minute (gpm). If the pump output is 50 gpm and the chemical uptake is 1 gpm,
the chemical dilution rate is 50:1. Determine how much area should be sprayed in 1 minute based upon this rate of chemical
uptake. Refer to the Dilution/Dosage Rate Chart
Do not dilute nor tank mix more chemical than is needed for the immediate area being treated. When diluting, wear gloves
and protective eyewear. Avoid splashing. Always add chemical to water, not water to chemical. Be sure mixtures and dilutions
are agitated before using. Use clean water to avoid clogging of hoses, screens and nozzles.
Timing of Treatment: Stage of plant growth, water temperature and weather conditions are the three main factors to be
considered in determining when to treat. This will vary according to climate. Most chemical applications provide optimum
effectiveness when plants are actively growing before flower and seed production. (One exception to this is Rodeo, which is
best applied to aquatic plants that are "at or beyond early-to-full-bloom stages of growth".)
For best results, most chemicals should be applied early in the day under sunny conditions. Water temperatures above 600F
(150C) are recommended. (One exception to this is Sonar where application is recommended "prior to initiation of weed growth
or when weeds begin actively growing".) Biological and chemical activity may be inhibited in colder water or under cloudy
weather conditions. Therefore, either reduced control or a much slower kill will result. Prior to application, check all
product labels for information regarding this.
Application Technique: Major concerns during application of chemicals are:
- Uniform distribution of the chemical within the intended treatment area.
- Avoiding drift from wind or wave action.
- Safety to the applicator and non-target plants and animals.
Treatments should be made from shoreline outward, generally from shallow water to deeper water. It is not necessary to cover every
square foot of treatment area since movement of the chemical under piers and rafts will occur naturally. Attempt to apply the proper
amount of chemical on the first pass over an area. However, if there is a problem with calibration or an applicator is inexperienced,
it is better to treat an area lightly and have to go over it a second time than to overdose on the first pass. It is against the law to
exceed maximum-labeled dosage rates, plus, overdosing is a waste of chemical.
Avoid treating under windy conditions or when strong winds are expected within a few hours after application. If there is a light wind,
treat with it at your back - never against it. Spray patterns should be adjusted to fairly large, uniform droplets and the nozzle angle
should never be tilted more than slightly upward. This will reduce or eliminate drift.
Spray technique may vary depending upon the type of vegetation being treated and the type of equipment being used. Heavy mats of filamentous
algae and/or combined masses of algae and plants are best treated with direct high-pressure sprays. This will facilitate breaking up of
surface matted plant materials and mixing of the chemical within the water column. Vegetation growing several feet below the water surface,
if not treated with granular products, is best controlled by injecting chemical beneath the water surface. This is accomplished by sub-merging
the spray nozzle or using a boom apparatus with drop hoses.
For floating-leafed or free-floating plants (water lilies, duckweed, etc.), effective coverage of the leaf surface with chemical spray is required.
Spray should be adjusted to fine droplets (avoiding misting). If working from a boat, care must be taken not to wash off chemical from the wake
caused by rowing or motoring. |
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Emergent plants treated with foliar sprays must be thoroughly covered with chemical solution. However, do not wet them to the point where run-off
from the surface occurs. Use a flattened (fan-type) spray of relatively small droplet size, if possible. Treat the distant plants first and work
"backwards" to avoid disturbing sprayed areas. If spraying from the waterside towards shore, care must be taken not to over-shoot target plants. |
Flowing Water: In flowing or re-circulating water systems, drip systems or metering devices must be carefully calibrated so that chemical additions
accurately dose the volume of water passing by. Chemical should always be added at a point of strong flow or turbulence to ensure effective
distribution and mixing. Calibration should be checked on a regular basis due to potential for equipment malfunction or variable water flow rates.
Another approach in canals or raceways is to stop water flow (impound) for a short time (3 to 6 hours), slug dose this section with the correct
amount of chemical and start up a drip system when flow is resumed. Number of systems and distance between them is usually a matter of trial and error.
Five to ten miles of control can sometimes be achieved from a single point of chemical introduction.
Refer to Drip System Calculation, Calibration, & Worksheet
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