3.1 Pesticide Types, Target Pest Groups & Modes of Action

3.1 Pesticide Types, Target Pest Groups & Modes of Action

The federal Core competency standards adopted by North Carolina in 02 NCAC 09L .0531 open the "Pesticides" competency area with a deceptively simple requirement: applicators must know the types of pesticides before they know anything about formulations, compatibility, or dilution. This section supplies that vocabulary. Everything in the rest of Chapter 3 — how a product is packaged, what adjuvants it needs, what it can be tank-mixed with — assumes you already know what kind of pesticide you are holding.

Start with the legal definition. Under FIFRA and the North Carolina Pesticide Law of 1971, a pesticide is any substance intended to prevent, destroy, repel, or mitigate a pest, and it also includes substances intended for use as a plant regulator, defoliant, or desiccant. That last clause matters: a chemical that does not kill anything — a tobacco sucker-control agent, a cotton harvest-aid defoliant — is still legally a pesticide, still requires registration, and can still be classified for restricted use.

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1. Pesticide Families by Target Pest Group

+-----------------------------------------------------------------------------+
|                     PESTICIDES NAMED FOR WHAT THEY CONTROL                  |
|                                                                             |
|   -CIDE = "to kill"                                                         |
|                                                                             |
|   INSECTicide ... insects        HERBicide ...... plants / weeds            |
|   FUNGicide .... fungi           RODENTicide .... rats, mice, voles         |
|   NEMAticide ... nematodes       ACARicide ...... mites and ticks           |
|   MOLLUSCicide . slugs, snails   BACTERicide .... bacteria                  |
|   AVicide ...... pest birds      PISCicide ...... pest fish                 |
|   ALGAEcide .... algae           PREDACide ...... predatory vertebrates     |
|                                                                             |
|   NON-KILLING PESTICIDES (still regulated under FIFRA):                     |
|   PLANT GROWTH REGULATOR / DEFOLIANT / DESICCANT / REPELLENT / ATTRACTANT   |
+-----------------------------------------------------------------------------+

[!TIP] Read the pest group off the exam question. Category exams and Core alike will describe a pest and expect you to name the correct product family. "A nematicide applied in-furrow" and "a fungicide applied to foliage" imply completely different placement, equipment, and re-entry considerations even when the formulation type is identical.

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2. Selectivity: What the Product Spares

Selective pesticides kill certain organisms while leaving others essentially unharmed. Non-selective (broad-spectrum) pesticides kill nearly everything within their range of activity.

Selectivity is not always inherent to the chemistry. Placement selectivity — a directed spray, a hooded boom, a wick applicator, a soil band — makes a non-selective product behave selectively. Timing selectivity — a dormant application, a pre-emergence treatment — does the same. These are the tools that let an applicator use an effective non-selective product without sacrificing the crop.

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3. Movement in the Target: Contact versus Systemic

+-----------------------------------------------------------------------------+
|                    CONTACT vs. SYSTEMIC: WHY IT CHANGES THE JOB             |
|                                                                             |
|   [CONTACT]                             [SYSTEMIC]                          |
|   - Kills only tissue it touches        - Absorbed, then translocated       |
|   - COVERAGE IS EVERYTHING              - Coverage matters less             |
|   - Finer droplets, higher volume       - Coarser droplets acceptable       |
|   - Fast visible effect                 - Slower; may take days             |
|   - Rain-fast only after drying         - Must be absorbed before rain      |
|   - Cannot reach roots or rhizomes      - Reaches roots, rhizomes, tubers   |
|   - Ex: paraquat, glufosinate,          - Ex: glyphosate, imidacloprid,     |
|     contact fungicides                    systemic fungicides              |
+-----------------------------------------------------------------------------+

• A contact herbicide burns down the foliage it wets. Perennial weeds regrow from untouched rhizomes, which is why a contact product on johnsongrass buys weeks, not control.
• A systemic herbicide moves in the phloem to the growing points and root system, which is why it kills perennials but needs an actively growing plant to translocate.
• A systemic insecticide taken up by the plant reaches sucking insects feeding on sap that a spray droplet never touched — and, critically, can reach nectar and pollen, which is the basis for the pollinator restrictions in Chapter 7.
• Stomach poisons must be ingested (most baits); contact poisons act through the cuticle; fumigants act through the respiratory system as a gas. A bait station relies on the pest's behavior, not on your coverage.

Practical rule: the more a product depends on contact, the more the calibration, nozzle selection, and spray volume decisions in Chapters 8 and 9 determine whether it works at all.

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4. Mode of Action and Resistance Group Numbering

Mode of action (MOA) is the specific biochemical process or site a pesticide disrupts — acetylcholinesterase inhibition, acetolactate synthase inhibition, sterol biosynthesis inhibition, sodium channel modulation. It is the level at which resistance develops, and it is the level at which rotation actually helps.

[!WARNING] Rotating brand names is not rotating mode of action. Two differently branded products from different manufacturers can carry the same group number and place identical selection pressure on the pest population. North Carolina's most consequential example is Palmer amaranth, which developed widespread resistance to Group 2 ALS-inhibiting herbicides and then to Group 9 glyphosate across the Coastal Plain. Check the group number on the label, not the label's color.

Resistance management practices that follow from MOA thinking — rotating groups, tank-mixing effective partners with different group numbers, applying full labeled rates, and integrating non-chemical tactics — are developed in Chapter 11.

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5. Legal Classification Is Not a Chemical Property

Finally, separate what a product is from how it is classified:

• General use pesticide (GUP): may be purchased and applied by the public, though applying it for hire in North Carolina still requires a commercial license.
• Restricted use pesticide (RUP): may be purchased and used only by, or under the direct supervision of, a certified applicator. EPA classifies RUPs federally; NCGS § 143-440 additionally authorizes the NC Pesticide Board to designate state-restricted use pesticides, and the list is maintained at 02 NCAC 09L .0502.
• Unclassified: 40 CFR 171.103(c)(1)(vii) expressly requires applicators to understand that a product may be neither general nor restricted use — it may simply be unclassified.

A product becomes restricted for reasons that have nothing to do with how it kills: acute applicator hazard, groundwater leaching potential, hazard to non-target organisms such as bees or fish, or a specific misuse history. Toxicity category and restricted use status are different things. A Category I signal-word product is not automatically an RUP, and an RUP is not automatically a Category I product.