8.4 Application Methods & Procedures

8.4 Application Methods & Procedures

Sections 8.1 through 8.3 covered the machine, its calibration, and safe mixing. This section covers the decision those chapters serve: how the product is placed on the target. The federal core competency standards at 40 CFR § 171.103(c)(7) require a certified applicator to know the application methods appropriate to different formulations and situations, and to select the method that delivers control while avoiding drift and non-target exposure.

The method is not a free choice. It is constrained on three sides: by the label (which may prohibit specific methods outright), by the formulation (a granule cannot be sprayed; a fumigant cannot be broadcast from a boom), and by the site (a row crop, a dense orchard canopy, a wall void, and a burrow system need different answers).

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Placement Patterns

Banding Math Worth Knowing

Banding is the clearest case where the application method changes the amount of product bought. If a broadcast rate is 2 pints per acre and the applicator bands a 10-inch strip on 30-inch rows, only one third of the surface is treated, so the field consumes roughly one third of the product — while the rate within the treated band is unchanged. Remember from Section 8.2 that for a banded application the width W in the calibration formula is the band width, not the nozzle spacing. Confusing the two is the most common banding calibration error.

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Soil Versus Foliar Placement

Foliar application places the product on plant leaves and stems. Coverage requirements depend entirely on whether the product is contact or systemic (Section 9.3).

Soil application places the product on or in the soil, where it is taken up by roots, contacts germinating weed seedlings, or reaches soil-dwelling pests. Soil applications usually need incorporation:

• Mechanical incorporation — tillage that mixes the product into the top few inches.
• Water incorporation — irrigation or rainfall that moves the product into the soil profile.

The New Mexico incorporation imperative. Chapter 6 established that New Mexico's high elevation, cloudless skies, and thin dry atmosphere produce intense ultraviolet irradiance, and that many soil-applied herbicides photodegrade on an exposed surface. Combine that with summer soil temperatures driving volatilization and it becomes a practical rule: a soil-applied product left lying on a hot, sunlit New Mexico surface for days is being destroyed, not stored. Label directions routinely require incorporation within a stated interval, and that direction is mandatory language.

The same arid conditions cut the other way for irrigation incorporation. Section 6.2 established that shallow water tables in the Rio Grande, Pecos, and Mimbres valleys sit only a few feet below the root zone during irrigation season. Over-irrigating to "water in" a mobile, water-soluble, low-$K_{oc}$ product pushes it straight past the root zone toward drinking water. Use the lightest irrigation set that satisfies the label.

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Chemigation

Chemigation is applying a pesticide through an irrigation system — center pivot, sprinkler, drip, or flood. It is efficient, it covers ground the equipment cannot enter, and it is absolutely gated by the label.

• If the label says "Do not apply this product through any type of irrigation system," chemigation is a direct violation of FIFRA Section 12(a)(2)(G) and the New Mexico Pesticide Control Act. There is no field judgment available; this is mandatory language.
• If the label permits chemigation, it will specify the required anti-contamination safety devices, which as Section 6.2 explained are imposed through the label's enforceable Directions for Use. The system must carry functional backflow prevention and interlocks so that a pump shutdown cannot siphon pesticide back into the well.
• Section 2(ee)(3) permits any method of application not prohibited by the labeling — which is exactly why an express chemigation prohibition ends the discussion, and why silence on a method generally permits it.

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Methods That Are Not Sprays

Fumigation is separately certified in New Mexico as Category 7C. Fumigant labels commonly require the certified applicator to be physically present during application, tarp sealing, and aeration, and — as Section 2.3 explained — telephone availability does not satisfy an express on-site presence requirement. Fumigants are colorless and often odorless, many carry a warning agent such as chloropicrin, and the acute inhalation hazard is the reason the category exists.

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Choosing the Method: The Exam Logic

A method-selection question is answered in this order:

1. Does the label permit the method? An express prohibition ends the analysis.
2. Does the formulation support it? A granule is not sprayed; a wettable powder is not dusted.
3. Where is the pest? Below ground, in the canopy, inside a wall void, in a burrow, on the seed.
4. What is the drift and non-target exposure? Directed, banded, spot, and injected applications reduce off-target movement compared with broadcast spraying; dusts and fine sprays increase it.
5. What is the smallest treated area that will achieve control? Spot and band treatments deliver the same control on the pest with a fraction of the total load — which is a resistance, cost, environmental, and liability win simultaneously.

Worked scenario. A pecan orchard has scattered patches of field bindweed in the drive rows and no weed pressure elsewhere. Broadcasting a translocated herbicide across the whole orchard floor would be legal if the label supports it, but it treats mostly clean ground, raises cost, increases the chance of contacting the pecan trees, and applies unnecessary selection pressure. Directed spot treatment of the patches in late summer, when the perennial is translocating sugars downward to its root system, delivers better control of the bindweed with a small fraction of the product and far less non-target exposure.