Pesticides & Pesticide Labeling
Applying pesticides correctly and safely requires knowledge and skills. It carries a load of special responsibilities. As one who applies pesticides or supervises other pesticide applicators, you must be sure pesticides are handled properly and safely. You must be familiar with all state and federal laws regulating the use, storage, transportation, application and disposal of pesticides.
Federal laws and regulations set the standards for pesticide use. States have the right to be stricter than federal law but not more lax. At the national level, the U.S. Environmental Protection Agency (EPA), established by the U.S. Congress in 1970, regulates the use of pesticides under the mandate of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). FIFRA was enacted in 1947 replacing the Federal Insecticide Act of 1910 and has been amended several times since then. The U.S. Department of Agriculture (USDA) regulated pesticides before EPA. FIFRA governs the registration of pesticides. No manufacturer can market a pesticide in the United States until EPA approves the registration request from the chemical company (registrant) wishing to market it. EPA bases registration decisions on data, submitted by the registrant, demonstrating that the pesticide will do what it is marketed to do and that the use will not result in “unreasonable human health or environmental effects.” Pesticides play an important role in the control of turf and landscape pests. As defined in FIFRA, pesticides are: “Any substance or mixture of substances intended for preventing, destroying, repelling or mitigating any insects, rodents, nematodes, fungi or weeds, or any other forms of life declared to be pests, and any substance or mixture of substances intended for use as a plant growth regulator (PGR) (see table at left), defoliant or desiccant.” According to the EPA, "The term pest means any insect, rodent, nematode, fungus, weed or any other form of terrestrial or aquatic plant or animal life or virus, bacteria or other micro-organism (except viruses, bacteria or other micro-organisms on or in living man or other living animals) which the Administrator declares to be a pest under section 25(c)(1)." Like medicines people use to ward off diseases, turf and ornamental pesticides are actually plant medicines.
“Pesticide” is a general term that refers to several different products that control specific pests. Pesticides include insecticides that control insects, herbicides that control weeds and fungicides that control disease-causing fungi. They also refer to bactericides that control disease-causing bacteria, algicides for controlling algae, nematicides for controlling nematodes and miticides for controlling mites.
Pesticide product labeling is the main method of communication between a pesticide manufacturer and pesticide users. The information printed on or attached to the pesticide container is the label. Labeling includes the label itself, plus all other information you receive from the manufacturer about the product when you buy it. The labeling may include brochures, leaflets and other information that accompanies the pesticide product. Pesticide labeling gives you instructions on how to use the product safely and correctly. Pesticide users are required by law to comply with all the instructions and directions for use in pesticide labeling.
When you purchase a pesticide, your first step in using the product is extremely basic: Read the label. The importance of this step cannot be stressed enough. The pesticide label is a legal document; its restrictions are enforceable. It provides information for the safe handling and proper use of a pesticide. It is your single-most important tool in using the product safely and effectively. Not only does it include information regarding application procedures and preventive measures, but it describes ingredients and antidotes.
A variety of products exists for most pest-control needs. You can use recommendations from manufacturer representatives, extension agents or pest-control advisors to determine the appropriate pesticides for your situation. In addition, various references also are available to help you make such pest-control decisions. For example, Grounds Maintenance magazine annually publishes its “Chemical Update” series. The tables on pages 93, 95 and 96, drawn from the 2004 “Updates,” list brands and manufacturers of pesticides to help you locate sources for chemicals (changes may have occurred since this information was compiled). However, never forget that it ultimately is your responsibility to apply pesticides properly—read the label of every pesticide you use and follow its instructions exactly.
Emphasizing the importance of label use, FIFRA dictates several provisions regarding pesticide use. FIFRA states:
1. Users cannot use any pesticide in a manner that is inconsistent with the label. For example, you only can use a product on sites that appear on the label. In addition, this provision means that you can’t use a product at a rate that is greater than that specified on the label.
2. The government can fine or imprison growers, applicators or dealers who deliberately violate the label restrictions.
Chemicals are classified as restricted use or non-restricted use. Figure 1 (see page 89) shows an example of a restricted-use pesticide label for a highly toxic (Category I) chemical product.
In addition to federal regulations, states may require supplemental labeling, which you must follow as well.
THE IMPORTANCE OF CERTIFICATION
Obviously, chemical manufacturers must comply with strict government requirements when labeling their products. But you, the user, must comply with government regulations as well. In fact, for those products labeled as restricted use, FIFRA allows only certified applicators— or persons under their direct supervision— to purchase or use those products. The certified applicator’s certification also must cover the chemical’s uses. (The restrictions on this requirement vary from state to state, so check with your local governmental authority on how this aspect applies to your business.) For certification, the test typically covers—among other topics—areas such as:
- The general format and terminology of pesticide labels and labeling
- Information that typically appears on pesticide labels
- The pesticide’s classification (whether it is a restricted-use or non-restricted-use product)
- The importance of using the pesticide consistent with its label instructions.
DETERMINING RESTRICTED USE
The classification of a pesticide as a restricted-use chemical is independent of its toxicity category. For example, the manufacturer might register a chemical as Toxicity Category III—which means it is not very toxic to humans. Nevertheless, this chemical might be highly toxic to birds. Therefore, EPA would restrict its use to only certified applicators. Another manufacturer might register a chemical as Toxicity Category I—highly toxic to humans. However, because of its formulation or use pattern, EPA may not require that the chemical manufacturer register this product as a restricted use. Why? Because the chemical may be only toxic to the eyes, so a precaution to wear goggles is sufficient to protect the applicator.
If the EPA does not require a manufacturer to register a pesticide as a restricted-use chemical, then that statement— restricted use—does not appear on the label. Also, whether the skull and cross-bones and the word Poison appear on the label depends on the toxicity category and not the classification.
The active ingredients in a pesticide are the chemicals that control the target pest. Most pesticide products you buy also have other ingredients, called inert (inactive) ingredients. They are used to dilute the pesticide; to make it safer, more effective and easier to measure, mix and apply; and to make it more convenient to handle.
Usually the pesticide is diluted in water, a petroleum-based solvent or another diluent. Other chemicals in the product may include wetting agents, spreaders, stickers or extenders. This mix of active and inert ingredients is called a pesticide formulation.
Some formulations are ready for use. Others must be further diluted with water, a petroleum-based solvent or air (as in air blast or ultra-low volume [ULV] applications) by users before they apply them. A single active ingredient often is sold in several different kinds of formulations. If you find that more than one formulation is available for your pest-control situation, you must choose the best one for the job. Before you make the choice, ask yourself several questions about each formulation:
- Do you have the necessary application equipment?
- Can the formulation be applied safely under the conditions in the application area?
- Will the formulation reach your target and stay in place long enough to control the pest?
- Is the formulation likely to harm the surface to which you will apply it?
To answer these kinds of questions, you need to know something about the characteristics of different types of formulations and the general advantages and disadvantages of each type.
Emulsifiable concentrates (EC or E). An emulsifiable concentrate formulation usually contains a liquid active ingredient, one or more petroleum-based solvents and an agent that allows you to mix the formulation with water to form an emulsion. Each gallon of EC usually contains 25 to 75 percent (2 to 8 pounds) active ingredient. EC’s are among the most versatile formulations. They are used against a range of agricultural, turf and ornamental, forestry, structural, food processing, livestock and public-health pests. They are adaptable to many types of application equipment, from small, portable sprayers to hydraulic sprayers, low-volume ground sprayers, mist blowers and low-volume aircraft sprayers.
Advantages of using ECs:
- Relatively easy to handle, store and transport
- Little agitation required—will not settle out or separate when equipment is not running
- Not abrasive
- Does not plug screens or nozzles
- Little visible residue on treated surface.
Disadvantages of using ECs:
- High concentration makes it easy to overdose or underdose through mixing or calibration errors
- May cause unwanted harm to plants
- Easily absorbed through skin of humans or animals
- Solvents may cause rubber or plastic hoses, gaskets and pump parts and surfaces to deteriorate
- May cause pitting or discoloration of painted finishes.
Solutions (S). Some pesticides’ active ingredients dissolve readily in a liquid solvent, such as water or a petroleum-based solvent. When mixed with the solvent, they form a solution that will not settle out or separate. Formulations of these pesticides usually contain the active ingredient, the solvent and one or more other ingredients. Solutions may be used in any type of sprayer indoors or outdoors.
Some solutions are ready-to-use (RTU) products that contain the correct amount of solvent when you buy them. No further dilution is required before application. These formulations, usually solutions in petroleum-based solvents, contain small amounts (often 1 percent or less) of active ingredient per gallon.
Other solutions are sold as concentrates (C or LC) that you dilute with a liquid solvent before you apply them. Occasionally the solvent is water, but more often the solvent is a specially refined oil or petroleum-based solvent. Some uses of solutions include:
- Structural pest control
- Shade-tree pest control
- Mosquito control.
Advantages of using solutions:
- No agitation necessary
- Relatively easy to handle, store and transport
- Little agitation required—will not settle out or separate when equipment is not running
- Not abrasive
- Does not plug screens or nozzles.
Disadvantages of using solutions:
- Limited number of formulations of this type available.
Flowables (F or L). Some active ingredients are insoluble solids. These may be formulated as flowables in which finely ground active ingredients are mixed with a liquid, along with inert ingredients, to form a suspension. Flowables are mixed with water for application and are similar to EC or wettable-powder formulations in ease of handling and use. They are used in the same types of pest-control operations for which you would use ECs.
Advantages of using flowables:
- Seldom clog nozzles
- Easy to handle and apply.
Disadvantages of using flowables:
- Require moderate agitation
- May leave a visible residue.
Invert emulsions. This mixture contains a water-soluble pesticide dispersed in an oil carrier. Invert emulsions require a special kind of emulsifier that allows the pesticide to be mixed with a large volume of petroleum-based carrier, usually fuel oil. When applied, invert emulsions form large droplets that do not drift easily. Invert emulsions are most commonly used in vegetation control along rights-of-way where drift to susceptible non-target plants is a problem.
Dusts (D). Most dust formulations are ready to use and contain a low percentage of active ingredient (usually 0.5 to 10 percent) plus a fine, dry, inert carrier made from talc, chalk, clay, nut hulls or volcanic ash. The size of individual dust particles varies.
A few dust formulations are concentrates and contain a high percentage of active ingredient. You must mix these with dry inert carriers before you can apply them.
You always use dusts in dry form, and they easily drift onto non-target areas. Agricultural applications sometimes use dusts. In structures, applicators use dust formulations in cracks and crevices and for spot treatments. Seed growers also use dusts widely in seed treatments. Plus, you often see dusts used to control lice, fleas and other parasites on pets and livestock.
Advantages of using dusts:
- Usually ready to use, with no mixing
- Effective where drift from spray might cause damage
- Require simple equipment
- Effective in hard-to-reach indoor areas.
Disadvantages of using dusts:
- Easily drift off-target during application
- Residue easily moves off-target by air movement or water
- May irritate eyes, nose, throat and skin
- Do not stick to surfaces as well as liquids
- Difficult to get an even distribution of particles on surfaces.
Baits (B). A bait formulation is an active ingredient mixed with food or another pest-attractive substance. The bait either attracts the pests or is placed where the pests will find it. Pests die by eating the pesticide in the bait. The amount of active ingredient in most bait formulations is quite low, usually less than 5 percent.
Baits are used inside buildings to control ants, roaches, flies and other insects and for rodent control. Outdoors, you’ll see them used to control snails, slugs and some insects, such as mole crickets, but their main use is for control of vertebrate pests such as rodents, other mammals and birds.
Advantages of using baits:
- Ready to use
- Don’t need to cover entire area because the pest goes to the bait
- Control pests that move in and out of an area.
Disadvantages of using baits:
- Can be attractive to children and pets
- May kill domestic animals and non-target wildlife outdoors
- Pest may prefer the crop or other food to the bait
- Dead pests may cause odor problem
- Other animals may be poisoned as a result of feeding on the poisoned pests.
It is important to remove baits when the pesticide becomes ineffective or they may serve as a food source for the target pest or other pests.
Granules (G). Granular formulations are similar to dust formulations except that granular particles are larger and heavier. The coarse particles are made from an absorptive material such as clay, corn cobs or walnut shells. The active ingredient either coats the outside of the granules or is absorbed into them. The amount of active ingredient is relatively low, usually ranging from 1 to 15 percent.
You most often use granular pesticides to apply chemicals to the soil to control weeds, nematodes and insects living in the soil. You also use granular formulations to control larval mosquitoes and other aquatic pests.
Advantages of using granules:
- Ready to use—no mixing
- Drift hazards low, and particles settle quickly
- Little hazard to applicator—no spray, little dust
- Weight carries the formulation through foliage to soil or water target
- Simple application equipment, such as seeders or fertilizer spreaders
- May break down more slowly than WPs or ECs through a slow-release coating.
Disadvantages of using granules:
- Does not stick to foliage or other non-level surface
- May need to incorporate in soil or water
- May need moisture to start pesticidal action
- May be hazardous to non-target species, especially birds that mistakenly feed on the grain- or seed-like granules.
Wettable powders (WP or W). Wettable powders are dry, finely ground formulations that look like dusts. You typically must mix them with water for application as a spray. You can often apply products, however, either as a dust or as a wettable powder—the choice sometimes is left to the applicator.
Wettable powders contain 5 to 95 percent active ingredients. Wettable-powder particles do not dissolve in water. They settle out quickly unless you agitate them constantly to keep them suspended.
Wettable powders are one of the most widely used pesticide formulations. You can use them for most pest problems and in most types of spray equipment where agitation is possible.
Advantages of using wettable powders:
- Easy to store, transport and handle
- Less likely than ECs and other petroleum-based pesticides to cause unwanted harm to treated plants and surfaces
- Easy to measure and mix
- Less skin and eye absorption than ECs and other liquid formulations.
Disadvantages of using wettable powders:
- Inhalation hazard to applicator while pouring and mixing the concentrated powder
- Require good and constant agitation (usually mechanical) in the spray tank and quickly settle out if agitation is turned off
- Abrasive to many pumps and nozzles, causing them to wear out quickly
- Difficult to mix in hard or alkaline water
- Often clog nozzles and screens
- Residues may be visible.
Soluble powders (SP or WSP). Soluble-powder formulations look like wettable powders. However, when you mix them with water, soluble powders dissolve readily and form a true solution. After you thoroughly mix them, no additional agitation is necessary. The amount of active ingredient in soluble powders ranges from 15 to 95 percent; it usually is more than 50 percent. Soluble powders have all the advantages of wettable powders and none of the disadvantages except the inhalation hazard during mixing. Few active ingredients are soluble in water.
Microencapsulated pesticides (M). Microencapsulated formulations are particles of pesticides (liquid or dry) surrounded by a plastic coating. You mix the formulated product with water and apply it as a spray. Once applied, the capsule slowly releases the pesticide. The encapsulation process can prolong the active life of the pesticide by providing a timed release of the active ingredient.
Advantages of using microencapsulated pesticides:
- Increased safety to applicator
- Easy to mix, handle and apply
- Releases pesticide over a period.
Disadvantages of using microencapsulated pesticides:
- Constant agitation necessary in spray tank
- Some bees may pick up the capsules and carry them back to their hive where the released pesticide may poison the entire hive.
- Water-dispersible granules (dry flowables) (WDG or DF). Water-dispersible granular formulations are like wettable-powder formulations, except the active ingredient is prepared as granule-sized particles. You must mix water-dispersible granules with water to apply them. Once in water, the granules break apart into a fine powder. The formulation requires constant agitation to keep it suspended in water. Water-dispersible granules share advantages of wettable powders except:
- They are more easily measured and mixed
- They cause less inhalation hazard to the applicator during pouring and mixing.
Fumigants are pesticides that form poisonous gases when applied. Some active ingredients are liquids when packaged under high pressure but change to gases when they are released. Other active ingredients are volatile liquids when enclosed in an ordinary container and so are not formulated under pressure. Others are solids that release gases when under conditions of high humidity or in the presence of water vapor. For turf and ornamental purposes, you use fumigants to control a broad range of pests (weeds, weed seed, insects and fungi) in the soil.
Advantages of using fumigants:
- Toxic to a wide range of pests
- Can penetrate soil
- Single treatment usually controls most pests in the treated area.
Disadvantages of using fumigants:
- In most cases, the target site must be enclosed or covered to prevent the gas from escaping
- Highly toxic to humans and all other living organisms
- Require the use of specialized protective equipment, including respirators
- Require the use of specialized application equipment.
As the word suggests, pesticides formulated as gels are in a semi-solid, gelatinous state. Manufacturers generally package gels in water-soluble bags or packets, allowing operators to easily and cleanly handle, mix and load the pesticide. This reduces hazards to the operator and container-disposal problems.
A disadvantage of gels, as with any pre-measured packaging, is that this limits you to using only the incremental amounts contained in each package. However, gels’ ease of use means you’ll probably see more products formulated this way in the future.
An adjuvant is a chemical you add to a pesticide formulation or tank mix to increase its effectiveness or safety. Most pesticide formulations contain at least a small percentage of adjuvants. Some of the most common adjuvants are surfactants—surface-active ingredients that alter the dispersing, spreading and wetting properties of spray droplets.
Some examples of common adjuvants are:
- Wetting agents: Allow wettable powders to mix with water
- Emulsifiers: Allow petroleum-based pesticides (ECs) to mix with water
- Invert emulsifiers: Allow water-based pesticides to mix with petroleum-based carriers
- Spreaders: Allow pesticide to form a uniform coating layer over the treated surface
- Stickers: Allow pesticide to stay on the treated surface
- Penetrants: Allow the pesticide to get through the outer surface to the inside of the treated area
- Foaming agents: Reduce drift
- Thickeners: Reduce drift by increasing droplet size
- Safeners: Reduce the toxicity of a pesticide formulation to the pesticide handler or the treated plant
- Compatibility agents: Aid in combining pesticides (and fertilizers) effectively
- Buffers: Allow pesticides to be mixed with diluents or other pesticides of different acidity or alkalinity
- Anti-foaming agents: Reduce foaming of spray mixes that require vigorous agitation.
CALCULATING AND CALIBRATING PESTICIDES
See the Appendix: Turf and landscape calculations for information on calculating the best buy, determining how much to add to a tank and calibrating sprayers and spreaders.
Choosing the proper spraying equipment can make pesticide application either a simple or a difficult task. The following set of guidelines will help you decide which sprayer features best match your needs. As you make your decisions, keep in mind your or your operator’s skill level in using the equipment. Some sprayers require additional training depending on the features you select.
When considering the purchase of spray equipment, several variables are important. You need to look at tank aspects, pumps, pump capacity, agitation method, strainers and filters, booms, nozzle bodies, sprayer monitors and controls, nozzle monitors, pressure gauges and safety aspects. Let’s consider each here.
Your first consideration when purchasing spray equipment is determining the size tank you need, as well as what materials you prefer for its construction. Common tank-construction materials include fiberglass, molded plastic and stainless steel. Most importantly, the tank material should be corrosion-resistant and compatible with the chemicals you apply.
To ensure ease in cleaning, look for a tank design that minimizes leftover spray mix in the bottom. This will help you avoid disposal problems. Some tanks have a built-in sump that helps empty them completely. Also look for a drain plug at the tank’s lowest point to ease cleaning.
Finally, the liquid level in the tank should be clearly marked, or the tank should have a sight gauge (visible from your seated position) that shows levels.
CHOOSING A PUMP
The pump on your sprayer must deliver adequate flow and pressure for all applications. It also should handle the desired chemicals with minimal corrosion and wear. Pumps generally fall into two categories: positive-displacement pumps and non-positive-displacement pumps. Positive-displacement pumps include roller pumps, diaphragm pumps and piston pumps. Non-positive pumps include centrifugal pumps (see Figure 2, page 98).
Roller pumps produce moderate flows and pressures. A slotted rotor, revolving in an eccentric case, holds the rollers. As the rollers pass the pump inlet, the cavities between and under them enlarge and draw in liquid. When nearing the outlet, the cavities contract—due to the eccentric housing—and force the liquid out of the pump.
Roller pumps handle a variety of pesticides and have low initial and maintenance costs. These pumps operate efficiently but, as pressure increases, their volume (output) decreases. If you primarily use wettable powders, a roller pump probably isn’t your best choice. Roller pumps are not well-suited to abrasive materials because they rapidly wear the pump housing, the rotor slots and the rollers. Replacing the rollers is easy but—depending on housing wear—may not restore the pump to its previously satisfactory working condition. Roller pumps with nylon rollers work well with most chemicals, but rubber rollers are slightly better if you must use abrasive materials with these units.
Centrifugal pumps create flow and pressure from an impeller’s centrifugal force. Liquid enters through the impeller’s center. As it spins, centrifugal force throws the liquid into a spiral passage leading to the outlet. The only moving parts in a centrifugal pump are the shafts and impellers.
The impellers operate at a high rpm to give rated performance. PTO-powered centrifugal pumps require speed-up drives and high engine rpms, which can waste fuel when spraying. An alternative is a pump powered by a hydraulic motor connected to the sprayers’ hydraulic system.
Centrifugal pumps last a long time—even with wettable powders—and produce a high flow volume that is ideal for hydraulic agitation in the sprayer tank.
Diaphragm pumps have at least one chamber sealed at one end by a membrane or diaphragm. The other end has an inlet and outlet valve. The diaphragm connects to a piston. As the piston moves, suction draws the liquid through the inlet valve by moving the diaphragm, which enlarges the chamber. The piston’s return forces the diaphragm inward, shrinking the chamber and propelling the liquid out. A compression chamber smoothes line pulses. Ask to add one if it isn’t already incorporated into the design of a pump you like.
Diaphragm pumps require minimal maintenance because less contact takes place between the spray material and moving parts. Nevertheless, you’ll need to periodically check the diaphragm for pinhole leaks that can cause problems and lower pressure. Ask whether the diaphragm pump you are considering will resist the chemicals you use. Abrasive materials are less likely to damage this type of pump.
Piston pumps propel liquid by a piston moving in a cylinder, similar to a combustion engine. The intake stroke draws the liquid in through one valve, and the output stroke forces the liquid through another valve. Piston pumps have either an internal or external air chamber (surge tank) to dampen pulsations in the liquid flow associated with each stroke. Without a surge tank, the spray will pulse rather than being applied in a steady flow.
Piston pumps develop high pressures, which can increase a sprayer’s versatility. However, the relative capacity of piston pumps is often low. Because higher-volume piston pumps are expensive, they normally use mechanical agitation instead of hydraulic agitation. As a professional applicator, look for larger-capacity pumps driven by an auxiliary engine. The large pumps—with 2 to 8 cylinders—achieve higher flow rates, and the multi-cylinder design produces more even flow.
THE IMPORTANCE OF PUMP CAPACITY
Look for a sprayer with a large enough pump to handle your capacity requirements. Due to mechanical inefficiencies, some pumps don’t pump at appropriate pressures to move sprayer chemicals. Thus, make sure you choose a pump with a capacity that is 50 to 75 percent higher than your calculated flow requirements. The pump should have sufficient capacity to supply several nozzles, provide hydraulic agitation (if used), return flow for self-cleaning strainers and bypass-type regulating valves, and offset pump wear.
HOW AGITATION AFFECTSCHEMICAL APPLICATION
The type of agitation you choose depends on the chemical formulations you apply. A uniform chemical application depends on a uniform tank mix. If the chemical separates from its carrier, you’ll apply unequal chemical concentrations. Therefore, all sprayers benefit from a tank agitator to maintain a uniform mix.
Two common types of agitation are hydraulic agitation and mechanical agitation.
Hydraulic agitation, commonly called jet agitation, uses part of the pump’s flow to create a mixing action in the tank. With this type of system, you need a pump large enough to provide the extra flow volume that the jet agitator requires. Typically, you can use 5 to 10 percent of tank volume to determine the necessary flow. The flow can be through a standard agitation nozzle or a specially designed siphon nozzle. The siphon agitation nozzle creates a venturi effect—or vacuum—that increases the nozzle’s discharge. This increases the mixing action by two-and-a-half times and is effective when the available flow is marginal.
Hydraulic agitation also can consist of a sparger—a pipe or tube with several discharge holes—in the tank’s bottom. Check that the hydraulic agitator is in the bottom of the tank so it sweeps all areas.
Units with hydraulic agitation also should have some type of flow-control device. Too much agitation creates foaming in the tank, while not enough creates unequal chemical concentrations. A flow-control valve in the agitation line allows you to adjust the flow for a given chemical mix.
Mechanical agitation is produced by paddles or propellers on the tank’s bottom. The sprayer’s power source or a 12-V electrical motor drives these mixers. Sprayers with piston pumps typically use mechanical agitators, because jet agitation requires a larger flow, which results in a more expensive piston pump. Any of these agitators, when properly designed and operated, will adequately agitate most pesticides.
STRAINERS AND FILTERS
Line strainers are an important part of the sprayer’s plumbing system. A properly placed and sized strainer can prevent your worst nightmare: plugged nozzles. Strainers come with different mesh sizes, which indicate the number of screen openings per linear inch. For example, strainers with mesh sizes of 100 and 200 have smaller openings than mesh sizes of 30 or 50.
For most positive-displacement pumps, you need a suction-line strainer—with a mesh size of 30 or 50—between the tank and pump. This type of strainer protects these pumps’ small, internal, moving parts.
On a centrifugal pump, you must ensure that the pump’s inlet is not restricted. Thus, look for a line strainer on the pressure side of the centrifugal pump. The strainer should have a 50-mesh screen. In this location, it will protect both the nozzles and the agitation system. Using a suction-line strainer, as suggested for positive-displacement pumps, could cause problems on a centrifugal pump because it could plug, which could cause pump cavitation. Pump cavitation causes premature pump wear, leading you to need a new pump sooner rather than later.
A feature that you’ll sometimes find on both non-positive- and positive-displacement pumps is a self-cleaning line strainer. This type of strainer directs a high-velocity flow past the screen face, which continuously washes particles into a separate, unrestricted bypass line. Typically, you need a system with 6 to 8 gpm through the bypass line for proper operation.
Some sprayer manufacturers also put a small line strainer—with a 100- or 200-mesh screen—on each boom section. These strainers reduce your need to clean nozzle-tip strainers by catching small particles that larger strainers did not catch.
Nozzle-tip strainers also are important. They are your last line of defense against nozzle plugging. These strainers come in an assortment of sizes and materials. The nozzle’s orifice size dictates the necessity for and the mesh size of a nozzle-tip strainer. See your nozzle manufacturer’s catalog for recommendations.
THE BENEFIT OF BOOM-CONTROL VALVES
Sometimes you need to spray an area that’s narrower than your boom’s full width. As a result, manufacturers offer booms divided into several sections with individual valves. These valves are either manual or electrical and control the flow to either the left, center or right boom section, or any combination.
Many of these turf sprayers have remote-control, solenoid- operated valves. These typically have about a 10-gpm capacity with a 5-psi pressure drop and about a 100-psi maximum. These systems are relatively inexpensive and, with proper maintenance, can give years of service.
More turf sprayers today offer remote-control-operated, motorized ball valves. Having larger passages, these valves typically have higher flow rates and higher maximum operating pressures than solenoid valves. Ball valves can be slightly more expensive than solenoid valves. However, they tend to be less maintenance-intensive in the long run.
Other sprayers use three-way valves. Available in both solenoid- and ball-valve-type, these units allow the system to maintain constant pressure when any boom sections are shut off. This places less strain on the sprayer system by reducing pressure spikes. A three-way valve system is a good feature if you constantly turn booms on and off.
Some sprayer manufacturers have turned to installing manifold-type control-valve systems on their sprayers. These make maintenance and repair of the valves easier by allowing you to replace or repair one without completely disassembling the hoses or pipes.
Booms are available in two basic types: wet and dry. A wet boom is one in which the fluid travels through the boom itself. Dry booms are those that use hoses to supply fluid from one nozzle body to the next. A boom-support member typically supports the nozzle bodies.
Choosing a unit with a sturdy boom made from strong corrosion-resistant material is a good place to start. However some booms have the following extra conveniences you may want to consider:
Automatic boom-height control. This type of unit uses sonar to monitor the distance from the boom to the ground. As the terrain changes, the boom adjusts automatically with actuators on each boom to maintain a constant application height. This is an important feature to consider because boom height is so important to maintaining good spray distribution.
Remote-control boom fold-up. This feature allows you to fold the booms without dismounting the sprayer. It is useful if you must drive your sprayer around many obstacles.
Shielded booms are becoming more popular due to the demand for better drift control. Shielded or hooded sprayer enclose the nozzle bodies or the entire boom section. These enclosures prevent the wind from carrying the small drops off target. This feature is great for drift control, but it may require the use of a nozzle monitor to inform you of a clogged nozzle because you won’t be able to see if they are working properly.
DIFFERENCES IN NOZZLE BODIES
Nozzle bodies come in many shapes and sizes. As with boom types, they are available for both wet or dry booms, with or without diaphragm check valves and with multiple- or single-nozzle outlets.
Diaphragm-check-valve nozzle bodies are a plus because they prevent nozzle dripping after you shut off the booms. This prevents chemical contamination on areas outside the spray zone.
Multiple-nozzle or turret-type nozzle bodies give you greater flexibility when it comes to changing spray tips or unclogging them. All you need is to index the turret to the next nozzle and resume spraying with minimal downtime.
MONITORING AND CONTROLLING
Sprayer-system monitors continuously sense the sprayer’s operation, measuring travel speed, pressure and flow. Using this information, the device calculates the application rate and other useful information, such as application swath width and gallons of spray mix in the tank. You can use this information to better control the spraying operation, resulting in more precise pesticide application and better pest control.
Most monitors today come with an automatic rate-control function. This controller calculates the actual application rate and constantly compares it to a pre-set desired rate. If the controller detects a discrepancy (error), it automatically adjusts the application rate (usually by adjusting flow). Some controllers have pre-set alarms that alert you if the error is too large to correct. These types of errors include speed varying too much for pressure compensation, hose or connection breaks, line-strainer plugs or other serious problems.
A NEW OPTION: NOZZLE MONITORS
Some new sprayers have monitors that sense flow at individual nozzles. When nozzle flow stops, due to plugging or a loss of pressure, a signal—such as a flashing light or a buzzer—alerts you. This helps you detect clogged nozzles you can’t see from your driver’s seat or nozzles located under hooded or shielded booms.
THE PRESENCE OF PRESSURE GAUGES
Look for a unit with a pressure gauge designed to measure liquid pressure in a range of about one-and-a-half to two times the maximum anticipated pressure. Another beneficial sprayer feature is a dampener between the gauge and the sprayer to smooth pressure pulsations. This makes the gauge easier to read and prolongs the life of moving parts. Liquid-filled gauges are preferable to dry gauges because the liquid dampens needle vibrations.
If you’ve now detailed the specific features you want your sprayer to have, you probably are ready to shop. Keep in mind that you may not find the perfect sprayer with all of the features described here. Nevertheless, you’re bound to find several that meet most of your requirements. At the very least, you know all the advantages and disadvantages of the various features, which can help you better balance which sprayer will be appropriate for your needs.