Chapter 14: Application Methods and Equipment

Hydraulic sprayers

Hydraulic (liquid) sprayers are the most common and widely used application equipment, since most pesticides are formulated to go out as a liquid spray mix. The carrier — the liquid the pesticide is diluted in — is most often water, though liquid fertilizers or oils are sometimes used. Regardless of size, every hydraulic sprayer works the same way: pressure, from a mechanical pump or compressed air, forces the spray mix to a delivery device such as a spray gun, a wand, or a boom with many nozzles. The spray droplets themselves are formed by the system pressure together with the nozzle type and the size of the orifice, the nozzle opening.

The four basic parts

It pays to know all the parts, so that when something goes wrong you can find and fix the problem. The basic parts common to all hydraulic sprayers are the tank, screens, pump, and nozzles. The tank holds the spray mix; a large bottom opening helps drain and clean it, and a large top opening helps with filling, cleaning, and inspecting. A tank agitation system matters because constant mixing produces a uniform spray mixture and an even application — especially for wettable powders or dry flowables. Screens filter grit and debris out of the water line and nozzles and should be cleaned regularly. The pump produces the flow of spray to the nozzles and applies agitation; its parts must resist corrosion and abrasion because abrasive formulations like wettable powders wear them down. Two pump rules stand out: never operate the pump above the manufacturer's recommended speeds or pressures, and remember that pumps depend on the spray liquid for lubrication and to prevent overheating — running one dry invites damage.

Nozzles and droplet size

Nozzles do a lot of the work, and no single nozzle type is best for every application, though some work well across a range. The nozzle tip determines the flow rate, the volume applied, the droplet size and pattern, the uniformity, the coverage on the target, and the drift potential. Nozzles are classified by the spray pattern they produce, and the orifice size affects droplet size and flow rate. When it comes to choosing, the pesticide label is the most important source of information — many labels, especially for herbicides, specify a droplet-size classification. If a label tells you to use a medium or coarse spray, you must configure your equipment to produce it by selecting the right nozzle type, size, and pressure; doing otherwise is a violation of the label. Beyond the label, application rate, spray pressure, and travel speed all play a large role, as do the pesticide type and mode of action, and you should remember that wettable powders and other suspensions are prone to clogging nozzles and screens.

The droplet-size trade-off is one of the most important ideas in the chapter. Droplet size strongly influences both coverage and drift, and the two pull in opposite directions. Smaller droplets give more thorough coverage, which is often essential for insecticides and fungicides. Larger, coarser droplets drift less, which is why you can often use larger droplets when targeting weeds and why a herbicide label might call for a coarse spray specifically to avoid drift. No single nozzle produces one exact droplet size, so the goal is to pick nozzles that produce the range of sizes the situation needs.

Granular applicators

Granular applicators are the other major equipment family, and the key difference is that you don't mix the product with a liquid — the pesticide goes out in its solid, granular form. They usually operate by gravity feed with an adjustable opening to regulate the flow, and they're available for band or broadcast application. The two common types differ in how they spread: rotary spreaders fling granules to the front and sides using a spinning disk or fan, while drop spreaders release granules straight down through holes that an adjustable sliding gate opens in the bottom of the hopper. Because they place product directly beneath the machine, drop spreaders typically offer more precise placement than rotary spreaders.

Application methods

Table 14.1 names the common methods, and it's worth being able to match each to its definition. Broadcast uniformly covers an entire area or field; band lays down parallel strips, such as between or over crop rows; and spot treats a very small area or single plant. Crack-and-crevice places small amounts into cracks and crevices in structures (using dusters and aerosols); foliar targets the leaves and stems of a plant; and basal directs herbicides to the lower areas of brush or small trees. Soil application goes directly onto generally bare soil; space application treats an enclosed area with fumigants, fogs, mists, or aerosols; and baits are gels, pastes, and solid baits used mainly for insects and rodents.

Maintenance and cleaning

Good upkeep protects you, your equipment, and your results. Proper cleaning and maintenance prevents breakdowns, increases equipment lifespan, decreases repair costs, helps ensure the proper application rate, and supports effective pest control. A crucial reason to clean is to avoid cross-contamination when switching pesticides — leftover residue from the first product can harm the plants you're protecting or contribute to incompatibility. A solid program means cleaning after each use and inspecting the hoses, connectors, hopper or tanks, pumps, screens, and all moving parts, plus a complete check at the beginning and end of each season. Clean the inside and outside thoroughly before switching pesticides, before any maintenance or repair, and especially before storing the sprayer for any length of time. Two safety rules are non-negotiable: never allow contaminated cleaning water to reach surface or groundwater, and wear appropriate PPE when checking, using, and cleaning, since contaminated surfaces and splashes can expose you to residue. When a product needs a specific cleaning procedure, the pesticide label and manufacturer information are your best source.

How to study this chapter

1. Anchor the two framing facts: equipment is as important as the pesticide, and its job is to deliver the proper rate uniformly.
2. For hydraulic sprayers, know that water is the usual carrier, pressure drives the mix to a delivery device, and droplets form from pressure + nozzle + orifice.
3. Memorize the four parts (tank, screens, pump, nozzles) and the two pump rules: never exceed the manufacturer's speed/pressure, and the liquid lubricates and cools it.
4. Nail the label rule for nozzles — a required medium/coarse spray is mandatory, and not producing it is a label violation.
5. Lock in the droplet trade-off: small = more coverage (insecticides/fungicides), coarse = less drift (weeds).
6. Separate the granular spreaders: rotary throws to the front/sides, drop goes straight down and is more precise.
7. Be able to match each application method to its definition (broadcast, band, spot, crack-and-crevice, foliar, basal, soil, space, baits).
8. For maintenance, remember clean after each use, season-start/season-end checks, clean before switching/servicing/storing, keep cleaning water out of surface and groundwater, and wear PPE.