Introduction
Southern commercial forests compete with a wide variety of undesirable grasses, weeds, trees and vines. These undesirables take needed growing space, water, sunlight and food.
Undesirables not only affect growth and yield of desired plants but may determine whether an important species can exist in some cases. Longleaf, slash and loblolly pine are three examples. They must have adequate space and sunlight to grow, just as farm crops do. They are called "shade intolerant." Examples of hardwood trees that need open space and sunlight are green ash and yellow poplar. Undesirables often include grasses, herbaceous weeds, brush, overly dense tree species and low-value trees.
Herbicides offer a safe, efficient, cost-effective forest management tool for controlling competing vegetation. Herbicides can increase the value of forest production by 50 percent or more. Most commercial forest acres need them at some time in a timber rotation. They have the potential for adding many extra dollars of income from a forest. The enjoyment of helping the forest and getting exercise are extra benefits obtained from working with "weed" control and forest improvement.
Because of different economic values and few selective treatments for hardwood stands, most undesirable vegetation control has been in pine stands, which are resistant to many herbicides and which have shown economic benefits. Weed control in hardwood stands is gaining interest and may become more common. You should certainly consider its benefits in high grade stands.
Most forest vegetation control has been conducted to prepare planting sites, control undesirables (tree release), improve natural regeneration, provide for fire protection, noxious tree control, for wild life management and improve forest range. Direct economic benefits are better crop tree survival and growth, more quality wood production, earlier harvest and shorter cutting cycles, reduced fire hazard and more income.
Many changes in vegetation control have occurred in the past 20 years. Chemicals have come and gone, equipment has improved and economic considerations have changed. Most of the changes have been positive. We now have greater flexibility than ever before with a large array of quality products for "weed" control.
Successful vegetation control has been accomplished by many different ways, such as chemical, mechanical, fire, natural means (such as grazing) or by a combination of these methods. No chemical is good for every plant species. Be aware of the "target" species on the site, and match the chemical and method of control to the prevailing conditions. Unless you're experienced, you should consult a local forester or county agent, observe the results of a nearby treatment or test on a trial basis for the desired treatment. With annual changes being made in prices, chemicals and equipment, consider reviewing the best match periodically.
An applicator must be certified as required by state and federal law before buying and using restricted herbicides. He should be familiar with the product label he will use. The label contains many items such as plants controlled, legal uses, safety considerations, how much to apply, application methods, etc. Parish LSU AgCenter agents or Louisiana Department of Agriculture and Forestry personnel can provide information about certification, applicable chemicals and sources of assistance.
Many chemical choices are available. A key consideration is the chemical action pattern. Some chemicals go into plant root systems through the soil after soil penetration following rainfall. Others are absorbed through plant foliage, through bark or stump, and some are injected into the cambium layer of the plant. Many chemicals can be used in several ways. Generally, soil active chemicals are longer lasting and have more opportunity to move off the specific site or harm desired vegetation than contact herbicides. Herbicide action may be selective (kill only certain plants), non-selective (harmful to most species), preemergent (prevents seed germination) or post-emergent (kills plants after they come up).
Forestry herbicides are safe to use when handled and applied properly. Many forestry herbicides are no more toxic to humans than salt or aspirin. Another factor adding to safety is that normally only a small amount of herbicide needs to be applied to a tract every 10 to 40 years. Be sure to follow all labels and precautions when using and storing herbicides. Keep safety and emergency supplies nearby in case of a problem.
Safety and application supplies needed are neoprene gloves, safety goggles, water, soap, towels, labels, flagging tape, funnel, mixing containers, measuring equipment, plastic disposal bags, first aid kit and spare equipment parts. Household ammonia will break down some chemicals and is often used to wash out equipment. A commercial rinse solution can also be used. Dispose of rinse water by applying to the spray site, or save it for another application. Mark and label all containers, and keep drinking water labeled and separate. Do not use herbicide sprayers for horticultural crop or plant sprays because of potential residues that may still be in the equipment.
Equipment should be maintained in good shape, and fittings, hoses and clamps should be kept tight and in good repair. A broken or leaking part can spill expensive chemicals or cause unnecessary problems.
Check, clean and repair equipment daily. Also review labels and check calibration often to prevent waste and problems. Be careful when transporting chemicals. Plan ahead, and carry control supplies in case of a spill. Store chemicals properly, and keep the storage facility locked.
Application Methods and Equipment
Many forest landowners practice their own weed control with sprayers, injectors, granular spreaders, soil spot applicators or hack-n-squirt equipment. All can be effective at a reasonable cost, especially when you do the work. Be aware of the limitations and benefits of each. Some are to be used seasonally on certain sizes of plants, species, soils and in specified ways.
Sprayers
Sprayers come in a number of types. Some people use common spray equipment mounted on farm tractors or ATVs for forestry work. These work well on smaller trees, brush or before planting when equipment can travel over the ground without interference from trees, debris, vegetation or terrain. Hand-operated nozzles can be used with sprayers for spot treatments. With tractor- or ATV-mounted sprayers, you should have some experience with the equipment and calibration procedures before using them in woodland situations. During the growing season, a number of herbicides can be used effectively with mounted sprayers.
Another sprayer adaptation is the "backpack mist blower," essentially a backpack spray container (usually 3- or 4-gallon size) with a small gasoline motor attached to propel the spray. Usually it blows out a fine spray or mist that can travel some distance. These sprayers may be difficult to calibrate, and the fine spray or mist can drift if not used carefully. Also, the small motors must be carefully maintained for satisfactory service. A number of herbicides and insecticides can be used with these applicators during the growing season.
Hand pump sprayers come in several types and brands. Backpack types are easier to carry and more convenient to use than hand-carried garden types. Backpack sprayers can be used effectively in many situations, such as foliage spray on low-growing vegetation, soil-spot treatment and basal or stump spray. They are useful in rough terrain and in sensitive areas. They can be acquired as piston type or diaphragm type. The piston sprayer will build up more pressure. The diaphragm type does not wear as quickly when using wettable powder chemical formulations. The diaphragm pump has enough pressure for most uses.
The backpack sprayer can be used to wet the foliage of lowgrowing vegetation for selective control. A number of nozzle types can be used to alter spray patterns, and an extension tube can be added to provide extra reach. A large variety of chemicals can be used during the growing season with this equipment. The applicator should determine the proper time of year to use a particular chemical and check calibration with each terrain and vegetation type. A marker dye can be used if needed to mark the vegetation to prevent skips or overlaps. A source of water for mixing is necessary, and only a limited amount of area can be covered per sprayer full. Backpack sprayers can be pumped without taking them off the back and are relatively trouble-free and simple. Often they are adapted with gun type, hand-operated nozzles to apply herbicides in soil spots or basal sprays (bark sprays). This adaptation allows you to carry a concentrated chemical to cover a significant amount of area or treatment.
Spot Guns
Several types of spot applicators are used to apply metered amounts of selective herbicide to the soil for absorption into target vegetation root systems. These controlled amounts of concentrated herbicide are applied in soil spots either on a grid pattern or to individual plants. For example, a common herbicide is often applied to the soil at 1 milliliter every 3 square feet or 1 milliliter per inch of tree diameter to individual trees.
Spot applicator use is as simple as walking along while squirting a certain amount of concentrated herbicide to the soil. Soil types and rainfall affect the herbicide speed and chemical activity. Similar application can also be made with hand nozzles on sprayers, but exact amounts of herbicide are more difficult to apply to spots. Spot applicators must be adjusted to deliver the proper amount of spray per squeeze.
Chemicals applied with spot applicators are soil active and usually selective. Be careful to avoid use on susceptible desirable vegetation, in wash-prone areas and along boundaries. Pine release can be conducted with this method by using selective herbicides at proper rates. Most soil spot chemicals are used only in the spring until about June.
Injectors
An old, reliable, cheap, common way of controlling undesired vegetation is with chemical injection into the cambium layer. Tube injectors are used by filling with chemical and sticking the bit into the stem base to form a cup. Injections should be made around the tree base with about 2-inch spaces between injections for most species. Some hard-to-control species, such as maple, require touching injections completely around the tree. When the injector cup is made, a metered amount of chemical is deposited in the cambium layer opened by the injector. Injection can be done during any time of year with a number of herbicides. Some herbicides are not quite as effective in some seasons or on certain species. Herbicide labels and publications will identify best uses and perhaps mixtures.
A kill of 85% to 95% of injected stems should result from injection. Injection, unless there is a root graft between trees, is selective on specific stems without danger of chemical drift, movement or harm to desirable vegetation. Trees deadened can be burned, cut or used without danger with common herbicides. Injection can be done on stems 1 inch DBH and larger but is most practical on larger stems because of time required to make frills.
Hack-N-Squirt
This method of tree control is similar to using tube injection and is an economical, effective method year around. With this method, an axe or hatchet is used to make "hacks" (injections) into the tree's cambium
layer. A plastic "squirt" bottle is used to spray a specific amount of herbicide into the cuts placed around the tree. Very little equipment is needed for usually good results. A spare bottle of herbicide can be carried to extend injection time between refills. Safety glasses, gloves and long sleeves should be worn for protection.
Hatchet Injectors
These automatic tools work similarly to the hack-n-squirt method. The herbicide container attaches to a belt or your back with a tube going to the hatchet. These hatchets have a spring mechanism that releases a metered amount of herbicide into the bark. Hacks are made around the tree as with a hatchet. Spare parts and regular cleaning are recommended to keep these hatchets working. These tools also can be used with a number of herbicides during all seasons without harm to desired vegetation. At least one type of hatchet injector inserts a herbicide cartridge into the tree at required spacing.
Granular Herbicides
Granular soil active herbicides have been used by ground applicators in some situations for a number of years. Granular materials are soil active, and some are species selective and can be used for pine release. They have been applied by special tractor spreaders, hand-operated spreaders or by hand. When using these materials, you must know the susceptible plant species on the site, calibration of doses, time of application and soil types. Be careful
along boundaries and drains. These materials so far have had limited ground use but are often used by aircraft because they have limited drift and filter through tree tops to the soil. Local areas and dense brush spots can be easily treated by granular ground methods. Granular materials may be selective or non-selective.
Basal and Stump Sprays
These techniques are selective and simple to use. Both use penetrating solutions to translocate to the cambium layer where the stem conducts the herbicide into the roots. A number of herbicides will work effectively, some of which must be mixed with diesel and surfactant. Others come ready to use. Disadvantages are the large volume of spray needed for a lot of stems and the difficulty of hitting the target in a dense area.
With basal sprays there are species, seasonal and stem size limitations. With basal (or streamline) methods, the lower trunk is either sprayed around or across with a penetrating herbicide that enters the cambium area. Usually thinbarked trees under 4 inches DBH are treated. Some thick-barked species such as blackjack oak are difficult to control by basal treatment.
Stump treatments are selective and effective, but penetrating herbicides must be applied to freshly cut stump cambium layers within several hours of cutting to prevent resprouting. Many herbicides will control sprouting by spraying fresh stumps. Equipment usually is a backpack sprayer with a spray nozzle, gun attachment or hand-carried sprayer.
Conclusion
Many chemicals and methods of application are available to landowners for vegetation control. They can be safe, cost-effective, simple and applicable year around. Some methods require little equipment or experience. Before using herbicides, be certified and know all the facts. Your parish LSU AgCenter Extension agent or forester can help you with proper application. Consider having the work done professionally by a contract applicator or by aircraft since work will be guaranteed and usually cost effective. Most commercial forests can be improved by herbicides and should be considered in management programs.
How To Mix Spray Material and Apply It Uniformly
For example, you wish to make a herbicide application with a hand-held or backpack sprayer, and the treatment calls for 2 pints of product in 15 gallons of water per treated acre applied in a band 4 feet wide over the top of planted seedlings. To spray a 4-foot band, you can use a 9504E Evenflo fan spray nozzle tip held 22 inches above the target surface, with 25-40 psi sprayer pressure.
It is almost impossible to calibrate a manual sprayer for an exact spray rate. Fortunately, the quantity of water is not critical, so you can calibrate your sprayer close to the desired rate and be satisfactory - but you must apply close to the recommended amount of herbicide per acre. For a 4-foot band, measure 85 linear feet (113 feet for 3-foot band or 68 feet for a 5-foot band) over the area to be sprayed (see following chart).
Then make several passes over the strip at a walking speed you can maintain while spraying the herbicide. Determine the average length of time required to cover the distance. Determine how many fluid ounces (fl.oz.) you apply during that length of time at your planned operating psi output. That number of fluid ounces translates directly to gallons per acre. Let's assume you determine that you will be applying 13 gallons of solution per acre.
Convert volumes to fl.oz. and use a simple ratio to reduce 2 pints product in 13 gallons water per acre to a proper 1-gallon mixture:
1 gal. = 16 cups = 128 fl.oz. = 3785 milliliters( ml)
1 qt. = 4 cups = 32 fl.oz. = 945 ml
1 pt. = 2 cups = 16 fl.oz. = 475 ml
32 oz. product : (1qt.) X oz. product = 2.46 oz. prod/gal of water
1664 oz. water 128 oz. water (1 gal.)
Water solubles or dispersibles, such as powders, are handled the same way. Assume a treatment of 6 ounces powdered chemical in 15 gallons of water per treated acre. Also assume the same actual spray rate of 13 gallons per acre.
6 oz. powder : X oz. powder = 0.46 oz. powder/ gal. water
1664 oz. water 128 oz. water
In such cases the product must be reduced to smaller units such as spoonfuls. For example: 1 oz. of powder = 3 slightly rounded tablespoonfuls (measuring, not kitchen) = 9 slightly rounded teaspoonfuls. Thus, the above example needs approximately 4 tablespoonfuls of powder per gallon of water.
To determine a % solution, such as 2% liquid spray, use the following formula: A 1-gallon 2% solution is 128 fl.oz. per gal. X 0.02 = 2.56 oz. product per gallon of water. Then calibrate the sprayer exactly as above for the application.
Another method of calibration is:
Spray Width and Distance Figures for Use in Calculating Gallons of Herbicide Per Acre
1) Measure off the number of feet of row for the respective row spacing:
|
Row Spacing |
Row Length Measured
(feet) |
Calculations |
|
5 ft. (5 ft.) |
68 |
The number of ounces water collected in the time to travel any of these distances equals the number of gallons applied per acre. |
|
4 ft. 8 inches (4.7 ft.) |
72 |
|
4 ft. 4 inches (4.3 ft.) |
79 |
|
4 ft. (4 ft.) |
85 |
|
3 ft. 8 inches (3.7 ft.) |
93 |
|
3 ft. 4 inches (3.3 ft.) |
102 |
|
3 ft. (3 ft.) |
113 |
2) Time the sprayer in seconds as it travels over the distance measured above. Then collect the water spray from all nozzles on one row in the same length of time with the vehicle in neutral. The vehicle throttle setting used both for timing the distance traveled and for collecting the spray should be the same as that to be used for spraying. Collect the spray from all nozzles on one row for the row length measured, and record in fluid ounces the quantity of water spray collected. Each fluid ounce of spray collected is equivalent to 1 gallon per acre of crop.
Example:
The measured spray width was 4 feet.
1. The calibration distance (see table) for a 4-foot band is 85 feet.
2. Walking the 85 feet required 28 seconds.
3. The nozzle sprayed 14 ounces in 28 seconds; therefore, the sprayer is applying 14 gallons per acre. Glossary of Terms Pertaining to Pesticides
Absorption - Penetration of one substance into another; also, the uptake of chemicals by plants through leaves, stems, roots, flowers or fruit.
Active Ingredient - A substance contained in a pesticide preparation which will, by itself, act in the same manner and for the same purposes as indicated by the directions for the preparation as a whole. Often listed as pounds per gallon of solution.
Adjuvant - A material added to a pesticide mixture to modify and improve performance. Characteristics modified may be viscosity, evaporation rate, droplet size, spreadability, etc. An adjuvant may come as part of the pesticide formulation or separately as a spray tank additive.
Adsorption - The process by which a pesticide or other chemical is held or bound to a surface by physical or chemical attraction.
Basal Treatment - Herbicidal treatment to stems of woody plants at and just above ground level so as to encircle the stem with a penetrating chemical.
Boom - A section of pipe or tubing to which several nozzles are placed to apply pesticide over a wide area at one time.
Boom Sprayer - Equipment used for applying a pesticide in liquid form. Consists of a tank, extended pipe (boom) supporting and carrying the liquid spray nozzles, and a pump to produce the desired pressure on the liquid as it flows to the nozzles.
Broadcast Application - Application of a pesticide uniformly over the area to be treated without regard to the arrangement of plants as in rows.
Calibration - Measurement of output or dispersal of application equipment and adjustment of equipment to control the rate of dispersal and the droplet or particle size of a pesticide dispersed by the equipment.
Carrier - An inert material that serves as a diluent, vehicle or solvent for the active ingredient or toxicant.
Certified Applicator - Commercial or private person qualified to apply restricted-use pesticides as defined by EPA regulations. Compatibility - The ability of two or more substances to mix without objectionable changes in their physical or chemical properties or without reducing the effectiveness of any individual component.
Concentration - Amount of active ingredient contained in a unit volume or weight of a formulation or mixture.
Contact Pesticide - A pesticide which results in the death of target plants, animals, insects or other organisms either from direct contact at the time of application or contact by the pest to residual deposit.
Deflocculator - A dispersing agent used to retard settling of solid particles in a suspension.
Diluent - A material, liquid or solid, used to dilute a toxicant to field use strength.
Dispersant - A material that reduces the cohesiveness of like particles, solid or liquid.
Displaced Swath - That portion of the spray which flares out on the downwind side of the boom and falls outside the target swath. Dosage - The amount of active chemical applied per unit area treated.
Drift - The movement of a portion of airborne particles of a dust or spray away from an intended point of application.
Droplet Size - The diameter size of the droplet usually measured in micrometers or microns.
EC50 - The median effective concentration (ppm or ppb) of the toxicant in the environment (usually water) that produces a designated effect in 50 percent of the test organisms exposed.
Emulsifiable Concentrate - A concentrated pesticide formulation usually consisting of a pesticide dissolved in an organic solvent and a surface active agent which permits direct dispersion of the total formulation in water.
Emulsifier - A surface active substance used to stabilize suspensions or dispersions of one liquid in another.
Emulsion - Suspension or dispersion of small droplets of one liquid in another.
Flowable Pesticide - A type of pesticide formulation in which very fine solid particles are mixed in a liquid carrier.
Foaming Agent - A chemical substance or adjuvant which aids in forming a foam. Also, anti-foam agents reduce or prevent foaming in spray tanks or mixtures.
Fog Mist Application - Application as a liquid aerosol dispersion having particles with volume mean diameters of 25 to 30 microns. Wet fog aerosols may extend to 100 microns.
Formulation - The prepared or formulated mixture of pesticides and other ingredients concocted to give proper results when used by the purchaser.
General Use Pesticide - A pesticide that can be purchased and used by the general public without undue hazard to the applicator and environment if the instructions on the label are followed carefully.
Granular Formulation - Small pellets (larger than dusts) usually formulated from inert clays and impregnated with a toxicant, measured by mesh size or number of grids per inch through which the pellets will pass.
Herbicide - A chemical agent that destroys or inhibits plant growth.
Incompatable - Two or more materials that cannot be mixed or used together.
Inert Ingredient - An ingredient lacking in activity, reactivity or effect.
Maximum Dosage -The largest amount of a pesticide chemical that can be used safely without damaging the plant, animal or object being protected and which will not result in excess residues.
Miscible Liquids - Two or more liquids capable of being mixed and which will remain mixed under most conditions.
Mist Application - A liquid application having droplets with a volume median diameter of less than 100 microns.
Monitoring - To check and keep track of all aspects of a pesticide application, including mixing chemicals, spray pressure, wind speed, pest reduction records, etc.
Nonionic - A class of surface active agents and other compounds that do not ionize in solution. Many emulsifiers or surfactants used in pesticide formulations are nonionic. Some herbicides require the addition of a nonionic surfactant.
Non-target - Any area, plant, animal or other organism at which a pesticide application is not aimed, but which may accidentally be hit by the chemical.
Non-volatile - A material which will not evaporate (turn into a gas) at normal temperatures and pressures.
Nozzle Orifice - The functional opening through which a pesticide formulation passes and is directed into the air. The orifice controls the flow rate and spray pattern as well as atomization. The circular orifice of cone nozzles is designated as D4, D5 (4/64ths, 5/64ths inch, etc.) and is specific to nozzles produced by Delavan and Spraying Systems Company. Fan or flat fan nozzles are designated with numbers to indicate fan angle and flow rate. An 8004 has a flow rate of 0.4 gal./ min. at 40 PSI and an 80 degree fan. Some brands also have color-coded designations.
Overlap - To extend over and cover part of the previous swath.
Persistence - The presence of a pesticide in its active state and in a measurable concentration. Measure of time a chemical is active.
Pesticide - A chemical agent that destroys pests. Common pesticides include insecticides, herbicides, fungicides and rodenticides.
pH - The hydrogen ion concentration of a substance. pH is expressed as a numerical value ranging from 0 to 14, with 7 being neutral. Numbers below 7 indicate the acidity of a solution, with 0 being the most acidic. Numbers above 7 indicate increasing alkalinity. pH of mixing water can affect spray activity. A pH of 6 to 8 is usually satisfactory.
Phytotoxicity - The degree to which a chemical or other agent is toxic to plant life. This may be specific to particular kinds or types of plants.
ppb - An abbreviation for parts per billion.
ppm - An abbreviation for parts per million.
psi - Pounds pressure per square inch.
Precipitate - A solid substance that forms in a liquid and settles.
A material that no longer remains in solution or suspension.
Rate of Application - The amount of material applied per unit (area or surface). Usually measured as per acre, per foot, per hour, etc. Sometimes referred to as dose or dosage.
Registered Pesticides - Pesticide products approved by the state and EPA for uses listed on the label. Some state registrations for local needs are referred to as 24(C).
Residue - Trace of a pesticide and its metabolites remaining on and in a crop, surface, soil or water; usually expressed as parts per mullion (ppm) or parts per billion (ppb).
Restricted-use Pesticide - A pesticide available for purchase and use only by certified pesticide applicators. Thus group of pesticides is not available for use by the general public because of potential high toxicities or environmental hazards associated with these materials when misused.
Selective Pesticide - A pesticide that controls only a few indicated pest species and is not as poisonous to non-target plants at recommended rates of application.
Sensitive Areas - Places where pesticides could cause harm or problems if not used with special care and caution. Examples: boundaries, houses, schools, roads, parks, ponds, streams and farmland adjacent to spray areas.
Solubility - The maximum quantity of one gas, liquid or solid material which will dissolve in a liquid solvent at a given temperature. Since solubility varies with temperature, it is usually expressed at a standard temperature such as 25 degrees C.
Spot Treatment - A treatment directed at specific plants or areas rather than a general application.
Spray Height - The distance between the target being treated and the spray boom.
Spreader - A substance which, when added to a spray mixture, will increase the area that a given volume of liquid will cover on a solid or on another liquid (often called a surfactant).
Sticker - An ingredient added to sprays or dust to improve their adherence to plants or other surfaces (often included with a spreader). Surfactant/Surface Active Agent - A material which, when dissolved in a liquid, has the property of changing the surface energy of this liquid or solvent. Usually the liquid solvent is water, and the change in surface energy is a decrease in surface tension. Surface active agents are generally called surfactants.
Susceptible Species - A plant that is affected by pesticides at rates listed on the label.
Suspension - Particles of a solid or immiscible liquid dispersed in a liquid or gas but not dissolved in it. Suspended so as not to settle out, but often requiring constant agitation.
Swath - The width of the area covered by a pesticide application making one sweep or one trip across a treated area.
Systemic Pesticide - Pesticide that is absorbed and translocated throughout the plant or animal rendering it toxic to pests.
Tank Mix - A mixture of two or more functional formulations in the spray tank so that these materials are all applied at the same time.
Target - The field, plants, animals or pests intended to be treated with a pesticide application.
Trade Name (Trademark Name, Proprietary Name) - Name given a pesticide or pesticide product by its manufacturer or formulator and distinguishing it as being produced or sold exclusively by that company.
Ultra Low Volume (ULV) - Pesticide formulation for application at a rate no higher than 0.5 gallon per acre.
Vaporization - The evaporation or volatilization of a liquid or gas into the atmosphere.
Viscoelastic Adjuvant - Viscosity-modifying agents which thicken water-based sprays, giving them a stringy characteristic. They typically increase the size of spray droplets on target and may reduce drift loss when used properly.
Volatility - The ability to become a vapor; that is, to evaporate or give off fumes.
Wettable Powder - A powdered chemical formulation containing sufficient surface active material (wetting agent) so that the powder will mix and be suspendible in water as a spraying material.
Wetting Agent - A substance (surfactant) which, when added to a liquid (usually water), increases its spreading and penetrating power by lowering the surface tension.