9.1 Selecting the Pesticide & Pre-Application Planning
Key Takeaways
Pesticide selection follows pest identification, never precedes it: the product must be labeled for the identified pest, the exact site, and the application method you intend to use.
Before mixing, an applicator must confirm the label permits the site, verify the restricted-use classification against their own certification category, and check every legal overlay — REI, PHI, rotational crop restrictions, buffer zones and Bulletins Live! Two.
Selection in Arizona is constrained by desert-specific factors: alkaline hydrolysis in high-pH water, heat-driven volatility above 90°F, coarse leach-prone soils, and the ADEQ Groundwater Protection List.
A written pre-application plan — product, rate, volume, target area, equipment, weather window, PPE, buffer distances and re-entry signage — converts label requirements into a checkable job sheet and is the applicator’s primary defence in a complaint investigation.
Selecting the Pesticide & Pre-Application Planning
Core Principle: Planning is not paperwork you do after deciding to spray — it is the decision. The National Core Manual devotes an entire chapter to it because most enforcement cases, drift complaints and crop-loss claims trace back to a choice made before the tank was ever filled. In Arizona, that planning chapter meets a desert: alkaline irrigation water, 110°F summer afternoons, gravelly soils over shallow alluvial aquifers, and a regulator that reads records.
The Selection Sequence
Selection is an ordered process. Skipping a step is how applicators end up applying a legal product illegally.
- Identify the pest first. Chapter 2 covered why: the product must be labeled for the organism you actually have. A miticide will not touch a thrips outbreak, and a soil-applied nematicide is wasted on a foliar pathogen. Identification also tells you the vulnerable life stage, which determines timing.
- Confirm the site is on the label. This is the hard legal line. FIFRA Section 2(ee) lets you treat an unlisted pest on a labeled site; it never lets you treat an unlisted site. "Ornamental turf" does not authorise the vegetable bed twenty feet away.
- Check the classification against your own credential. A restricted use product requires certification in the correct category. A Category 3 Ornamental & Turf certification does not authorise a Category 6 fumigant, and an agricultural certification does not authorise structural work for hire — that requires PMD licensing.
- Read the whole Directions for Use. Maximum single rate, maximum seasonal rate, minimum spray volume, maximum number of applications, minimum retreatment interval, and application method restrictions are all independently enforceable.
- Collect the legal overlays. Restricted-Entry Interval, Pre-Harvest Interval, rotational crop (plant-back) restrictions, pollinator language, groundwater advisories, spray drift management statements, and any Endangered Species Protection Bulletin obtained from Bulletins Live! Two within six months of the application.
- Check Arizona-specific limits. A.R.S. § 3-365 buffer zones for odoriferous and highly toxic products; A.R.S. § 3-3606 school and child care notice; the ADEQ Groundwater Protection List; and any Section 24(c) Special Local Need label, which you must physically possess at the site.
Arizona Selection Constraints
| Desert factor | Effect on product choice |
|---|---|
| Alkaline carrier water (pH 8.0+) | Ester herbicides, organophosphates and carbamates hydrolyse in the tank. Either buffer the spray solution to pH 5.5–6.5 or select a chemistry that tolerates alkaline water. Never mix and hold overnight. |
| Heat above 90°F | Emulsifiable concentrates raise phytotoxicity risk; volatile formulations increase vapour drift. Shift to low-volatility esters, amine salts or encapsulated products, or move the job to the evening window. |
| Low humidity, high evaporation | Fine droplets shrink and drift. Choose coarser droplet spectra and drift-reduction adjuvants; this constrains nozzle and pressure choices at selection time, not just at calibration. |
| Coarse alluvial soils, shallow aquifers | Prefer products with stronger soil binding and shorter dissipation half-lives on gravelly ground near wells or riparian corridors. |
| Africanized honeybees and year-round bloom | Bee-toxic chemistry needs an evening window and weed management, not just a label glance. |
Tank-Mix Decisions Belong to Planning
Compatibility is decided before the tank is filled, not discovered in it. Section 3.3 covered the jar test and the W-A-L-E-S sequence; the planning question is narrower:
- Does any label prohibit the combination? A prohibition on one label binds the whole mix.
- Do the labels agree on rate basis? One product priced per acre and another per 100 gallons will not reconcile unless you fix the spray volume first.
- Is the mix legal for every site in the tank? If you plan to move between blocks, the mix must be labeled for all of them.
- Can you use the whole batch today? Arizona heat degrades many mixes within hours. Mix what you will apply.
The Written Pre-Application Plan
A plan is a job sheet you can hand an inspector. At minimum it captures:
- Customer, site and legal description or address; target pest and identification basis
- Product trade name, EPA registration number, formulation, and restricted-use status
- Rate, spray volume, total tank load, and the acres or square footage the load covers
- Equipment, nozzle type and size, operating pressure, ground speed and boom height
- Planned weather window, with the wind speed and direction range you will accept
- PPE required by the label, and the decontamination supplies on the truck
- Buffer distances from residences, schools, health care institutions, wells and surface water
- REI, posting or notification obligations, and who is responsible for each
- The Bulletins Live! Two bulletin, printed and dated
Why this matters beyond the exam: in a drift or exposure complaint the PMD or OES inspector reconstructs your decisions. A pre-application plan showing you checked the buffer, chose a coarse droplet spectrum and waited for a 4 mph wind is the difference between a notice of correction and a civil penalty.
An Arizona applicator holds a label for a herbicide registered for "ornamental turf." A homeowner asks them to also treat weeds in an adjacent raised vegetable bed with the same product. What does FIFRA permit?
Nothing — the vegetable bed is not a labeled site, so applying the product there is use inconsistent with the labeling under FIFRA Section 12(a)(2)(G), regardless of rate
The application is permitted under Section 2(ee) because the applicator will use a lower rate than the turf rate
The application is permitted if the applicator posts a 30-day re-entry sign on the vegetable bed
The application is permitted because weeds are a labeled target pest for the product
Why does carrier-water pH deserve attention at the product-selection stage in Arizona rather than only at mixing?
Because high pH water is legally prohibited as a pesticide carrier under A.A.C. Title 3
Because alkaline water above pH 8.0 hydrolyses ester herbicides, organophosphates and carbamates, so the water chemistry can rule an otherwise suitable product out before it is ever purchased
Because pH determines the restricted-use classification of the finished spray solution
Because alkaline water increases the Pre-Harvest Interval by 48 hours for all products
An applicator plans a tank mix of two products for a job that will move across three different crop blocks during the day. Which planning question is decisive for the legality of the mix?
Whether the two products share the same manufacturer and therefore the same emulsifier system
Whether the combined cost per acre stays below the customer’s approved budget
Whether the mixture is labeled for every site that will be treated from that tank, and whether either label prohibits the combination
Whether the mix can be held in the tank for at least seven days without separating
What is the primary practical value of a written pre-application plan when AZDA investigates a drift complaint?
It transfers legal liability for the application from the applicator to the customer who signed it
It exempts the applicator from the buffer zone requirements of A.R.S. § 3-365
It replaces the requirement to keep application records under A.A.C. R3-8-501
It is contemporaneous evidence of the decisions the applicator made — product, rate, droplet spectrum, buffer distances and the accepted weather window — before the application began
Sections you finish are checked off in the contents.