13.1 Sprayers, Nozzles, Granular, and Other Equipment
Key Takeaways
- Georgia Rule 40-21-3-.01 General Standard 6 requires every commercial applicator to know equipment types, advantages and limitations, uses, maintenance, and calibration.
- National Core Chapter 11: worn spray nozzles increase output; replace a full nozzle set when flow is about 10% or more above the new-tip catalog rate.
- Centrifugal pumps deliver high volume at relatively low pressure and tolerate abrasive wettable powders; roller pumps wear on abrasives; piston pumps build high pressure; diaphragm pumps handle many corrosive and abrasive mixes.
- Tapered flat-fan nozzles are for overlapping boom broadcast; even flat-fan nozzles are for bands and must not be overlapped the same way.
- Georgia row-crop cotton and peanuts typically use hydraulic boom sprayers; pecans and peaches typically use airblast; wick/wiper, granular, backpack, and injection tools each have a different calibration and drift profile.
13.1 Sprayers, Nozzles, Granular, and Other Equipment
Georgia Rule 40-21-3-.01 lists equipment as General Standard 6 for every commercial category: types of equipment, advantages and limitations, uses, maintenance, and calibration. The National Pesticide Applicator Certification Core Manual (2nd ed.) teaches the same domain in Chapter 11. You will not pass the General Standards sitting by naming a sprayer brand. You pass by matching the tool to the Georgia job—cotton and peanut booms in the Coastal Plain, pecan and peach airblast in south-central orchards, backpacks on landscape and rights-of-way, granular spreaders on soil insecticides, wick bars on tall escapes, and injection where the label and O.C.G.A. § 2-1-4 anti-siphon rules allow chemicals into irrigation water.
This chapter is GDA commercial applicator equipment under Rule 40-21-3. It is not the Georgia Structural Pest Control Commission Certified Operator exam (HPC/WDO/FUM). Do not study termite rigs here and assume they satisfy GDA General Standards.
Hydraulic boom sprayers
A hydraulic boom sprayer is the workhorse for broadcast and banded sprays on cotton, peanuts, soybeans, and forage. Dilute spray is pumped through a boom of nozzles at a chosen pressure. Advantages: uniform broadcast coverage when nozzles overlap correctly, high acres per hour, and a gallons-per-acre (GPA) figure you can prove with a catch test. Limitations: boom height and nozzle spacing must stay consistent; worn tips, plugged screens, and speed changes wreck uniformity; boom bounce on rough pecan middles or peanut beds produces skips and hot streaks.
Handheld and backpack sprayers suit spot treatments: palmetto and privet on a right-of-way, fire-ant mounds at a pecan shop, or a small ornamental bed under Category 24. Advantages: portable, relatively inexpensive, precise placement. Limitations: operator fatigue, highly variable walking speed, and a pattern that is only as good as the person swinging the wand. Backpack GPA still must be calibrated—walking speed is the miles-per-hour term in that calculation. A “walk until the tank is empty” habit is not a rate.
Airblast, granular, wick, and injection
Airblast (air-assist) sprayers use a high-volume fan to blow droplets into tree canopies. Georgia pecan and peach operations use them because a field boom cannot push spray into a 40-foot canopy. Advantages: canopy penetration and coverage of both leaf surfaces when air volume, deflectors, and travel speed match the orchard. Limitations: large drift potential on the downwind side, poor performance in still inversions, and a pattern that changes with every missing tree and every gust. Never treat an airblast like a boom: output is not “one nozzle GPM times boom spacing” in the same simple way. You still calibrate by catching nozzles or by tank-use over known acres, and you still follow the label’s GPA or dilute-volume directions.
Granular spreaders apply dry granules. Drop spreaders meter a sharp-edged strip; rotary (broadcast) spreaders throw a wider swath. Advantages: no spray tank mix, little liquid-droplet drift, useful for some peanut soil insecticides and turf products. Limitations: granules bounce and roll, patterns are sensitive to spinner speed and height, humidity can cake product, and you cannot see a spray fan—so catch pans or a tarp are the calibration method (13.2).
A wick or wiper (rope-wick, roller, or carpet wiper) wets weeds that stand above the crop with a concentrated herbicide, often glyphosate, without spraying the crop canopy. Advantages: almost no spray drift; useful on johnsongrass in pecans or tall escapes in cotton. Limitations: height selectivity only—weeds must be taller than the crop; wicks clog and dry unevenly; the rate is not a boom GPA and must follow the wiper directions on the label.
Injection includes tree injection, soil injection, and chemigation (injecting into irrigation). Advantages: placement in the plant or root zone and, for some uses, less foliar drift. Limitations: specialized metering, phytotoxicity if concentration is wrong, and—when injecting into irrigation—Georgia’s Anti-Siphon Device Act, O.C.G.A. § 2-1-4, requires a check valve plus low-pressure drain between the pump and the injection point. Using an unequipped irrigation system to apply pesticide is unlawful (administrative penalty up to $1,000 per violation). Chemigation method details continue in Chapter 14; the equipment point here is that injection is a different machine with extra Georgia hardware duties.
Tanks, strainers, gauges, and hoses
The tank must hold the load, resist the formulation, and allow agitation. Emulsions and true solutions need less violent mixing than wettable powders (WP) and dry flowables (DF), which settle without continuous agitation. A hydraulic bypass jet can suffice for many solutions; mechanical paddles or a well-designed hydraulic system are safer for WP suspensions. A tank that cannot keep WP in suspension will deliver a weak spray at the start of the field and a sludge overdose at the end—both are label problems.
Strainers (filters) protect the pump and nozzles. A typical stack is a tank-opening basket, a suction or pressure-line strainer, and a small nozzle screen behind each tip. Mesh must match the orifice: a screen finer than the orifice protects the tip; a screen coarser than the orifice lets particles through to plug the tip. Clean strainers on a schedule. A plugged line strainer drops pressure at the boom even when a cab gauge still looks healthy if that gauge is upstream of the clog.
A pressure gauge belongs where it tells you boom or nozzle pressure, not only pump pressure. Gauges fail. If the needle never moves when you change RPM or the regulator, replace the gauge before you trust a calibration. Hoses must be pesticide-rated for the pressure you actually run. A burst hose is a spill, an exposure, and—if you are a contractor or a commercial applicator using RUPs—an unexpected-occurrence record under Rule 40-21-5.
Pumps: roller, piston, diaphragm, centrifugal
National Core Chapter 11 expects you to match pump type to volume, pressure, and formulation abrasion.
| Pump | Typical job on a Georgia rig | Strength | Main limitation |
|---|---|---|---|
| Roller | Small to mid hydraulic booms spraying solutions and many ECs | Inexpensive; moderate pressure (often up to about 300 psi) | Rollers wear fast with abrasive WP/DF; output falls as rollers round off |
| Piston | High-pressure handguns, some orchard and high-pressure boom work; can handle WP | Positive displacement; can reach very high pressure (hundreds of psi) | Pulsation may need a surge chamber; closed-valve overpressure risk; cost |
| Diaphragm | Boom and orchard sprayers with abrasive or corrosive mixes | Positive displacement; diaphragms isolate the pump innards from the mix | Diaphragms crack with age and incompatible solvents; check valves need service |
| Centrifugal | Large tanks, high-volume low-pressure booms, WP/DF suspensions | High volume, relatively low pressure; no tight-fitting rollers to grind on powder | Not positive displacement; output falls as pressure rises; usually not self-priming; cannot build very high pressure |
Exam trap: a centrifugal pump is the high-volume, low-pressure choice that tolerates abrasives. A piston pump is the high-pressure positive-displacement choice. A roller pump is inexpensive but a poor season-long match for wettable-powder peanut fungicides.
Nozzles
The nozzle meters flow and sets droplet size and pattern. Chapter 11 expects you to pick the pattern for the job:
- Tapered flat-fan: boom broadcast. The pattern is heavy in the center and tapers at the edges so adjacent nozzles overlap (commonly about 30–50 percent depending on the tip and boom height). Conventional flat fans often run in the 30–60 psi range.
- Even flat-fan: band over the row or a strip. The pattern is uniform across the width. Do not overlap even-fan bands the way you overlap tapered fans, or the overlap strip is a double rate.
- Flood (flooding fan): wide angle, larger droplets, often lower pressure. Used for many soil-applied herbicides and fertilizer suspensions. Pattern uniformity is sensitive to boom height.
- Cone (hollow-cone and full-cone): directed sprays and airblast orchard work. Hollow cones produce a ring of relatively fine droplets for canopy coverage; full cones fill the center for drench-type directed work.
- Air-induction (venturi): mix air into the droplet. Larger, air-filled droplets reduce drift compared with a conventional fine flat fan at similar GPA. They need enough pressure to make the venturi work—starving an air-induction tip of pressure defeats the design.
Nozzle material matters. Brass is cheap and wears fast with WP. Nylon/plastic is economical. Stainless steel lasts longer. Ceramic is hardest and holds orifice size longest under abrasion.
Worn nozzles increase output — worked numbers
Catalog flow for a tip is 0.40 GPM at 40 psi. A catch test on a Sumter County cotton boom shows 0.46 GPM at the same pressure.
Percent over catalog = (0.46 − 0.40) ÷ 0.40 = 0.15 = 15 percent. National Core teaching is to replace the entire set when flow is about 10 percent or more above the new-nozzle rate. Replacing only the worst tip leaves mixed patterns and striped fields.
At 6 MPH and 20-inch spacing (the boom formula is taught in full in 13.2):
New GPA = (0.40 × 5940) ÷ (6 × 20) = 2376 ÷ 120 = 19.8 GPA
Worn GPA = (0.46 × 5940) ÷ 120 = 2732.4 ÷ 120 = 22.8 GPA
That is about 3 extra gallons per acre. If you mixed as if you were still at 19.8 GPA, every acre receives more mixture—and more active ingredient—than you calculated. Worn tips increase output. They do not “wear out and put on less” as a general rule. Plugged tips put out less; worn tips put out more. The General Standards exam loves that contrast.
Maintenance Georgia expects you to name
Flush tanks and booms at the end of the day. Never let WP sit overnight without agitation. Replace cracked hoses, leaking fittings, and fogged gauges. Keep spare strainer sets and a matched nozzle set on the truck. After any nozzle change, you recalibrate—that is section 13.2. Rule 40-21-5 records for contractors include equipment type; the machine you list should be the machine you actually calibrated.
Match the equipment to the site: a hydraulic boom on 12-row cotton, airblast in a peach block, backpack on a county-park bed, drop spreader along a sidewalk, wick on johnsongrass above peanut foliage, injection only with the label and Georgia anti-siphon hardware. Equipment selection is a Rule 40-21-3 competency, not a category luxury.
On a large Georgia peanut boom spraying wettable-powder fungicide, which pump type is chosen for high volume at relatively low pressure and for the absence of close-fitting rollers that grind on abrasive particles?
A Crisp County cotton applicator’s catch test shows several boom nozzles delivering 14 percent more flow than the catalog rate at the same pressure. What is the most important field consequence?
Which nozzle is designed for band applications over the row, with a uniform non-tapered pattern that should not be overlapped the way broadcast flat fans are overlapped?