12.1 Types of Pesticides and Modes of Action
Key Takeaways
- 40 CFR 171.103(c)(5)(i) and (v) require Core knowledge of pesticide types and of factors that influence effectiveness or lead to problems such as pesticide resistance.
- Classify first by target organism: insecticides, herbicides, fungicides, rodenticides, nematicides, miticides, molluscicides, antimicrobials, and plant-growth regulators — then confirm the New Jersey category and the labeled site and pest.
- Contact pesticides must hit the pest or the treated surface; systemic products are absorbed and translocated. A contact spray will not reliably control a pest feeding inside plant tissue or a weed whose growing point you never wet.
- Selective products spare a labeled crop, turfgrass, or beneficial; nonselective products kill a broad range of plants or pests. Turf vegetation control on industrial sites, airport runways, and dams is Category 6A work, not 3B.
- IRAC, HRAC, and FRAC group numbers name the mode of action. Two brands in the same group are the same resistance pressure; rotate groups, not just trade names.
Quick Answer: 40 CFR 171.103(c)(5) is the Core pesticide-characteristics standard. This section covers types of pesticides and the resistance and effectiveness factors in (c)(5)(i) and (v). Name the product by what it is registered to control, then by how it moves and how it kills. The New Jersey category, the labeled site, and the Insecticide Resistance Action Committee (IRAC), Herbicide Resistance Action Committee (HRAC), or Fungicide Resistance Action Committee (FRAC) group must all fit before anyone opens a jug.
N.J.A.C. 7:30-6.2 requires the commercial Core examination to include every 40 CFR 171 knowledge area. 40 CFR 171.103(c)(5) is not a vocabulary list. It is the reason a closed-book item will ask whether a contact insecticide can replace a systemic one, whether a selective turf herbicide belongs on an airport runway, or whether two different brands in the same IRAC group count as a resistance rotation. Use inconsistent with labeling remains illegal under FIFRA Section 12(a)(2)(G) and N.J.A.C. 7:30-10.2(a) even when the crew “meant” the right pest class.
Classify first by target organism
A pesticide is a substance or mixture intended to prevent, destroy, repel, or mitigate a pest, or intended for use as a plant regulator, defoliant, or desiccant. The Core still expects you to name the working types by target:
| Type | Target | Typical New Jersey setting |
|---|---|---|
| Insecticide | Insects | Category 7A household, 8B mosquito, 3A ornamental, 1A crop |
| Miticide (acaricide) | Mites and ticks | Ornamentals, turf, some public-health work |
| Herbicide | Plants (weeds) | 3B turf, 3A ornamental, 6A general vegetation, 6B right-of-way |
| Fungicide | Fungi | Turf disease, ornamental, some agricultural and seed uses |
| Rodenticide | Rodents | Structural 7A, some public-health and agricultural sites; bait rules in N.J.A.C. 7:30-10.3 |
| Nematicide | Nematodes | Soil and some greenhouse or agricultural sites |
| Molluscicide | Slugs and snails | Ornamentals, some turf and ag |
| Antimicrobial | Bacteria, viruses, other microbes | Category 12 water sanitization and sterilization |
| Plant growth regulator, defoliant, desiccant | Plant growth or foliage | Production agriculture, some turf and ornamental labels |
| Fumigant | Pests reached as a gas | Category 7C and other fumigation; extra certification under 40 CFR 171.103(c)(7)(ii) |
An insecticide that is also labeled for mites is still used only for the pests and sites on that label. 40 CFR 171.103(c)(4) already required correct pest identification; this section adds the product-class decision. A fungicide does not become an insecticide because “something is chewing the leaves.” A rodenticide does not become a crack-and-crevice insecticide because the customer saw droppings and beetles in the same room.
New Jersey categories follow use site and activity, not the word on the jug alone. A selective lawn herbicide used on residential turf is classic 3B. The same active ingredient used to strip vegetation on industrial sites, airport runways, or dams is Category 6A work under the Rutgers PAT / N.J.A.C. 7:30-6.3 overlay. Holding 3B does not authorize that industrial vegetation job. Holding 7A does not authorize 7C structural fumigation. Type of pesticide, category, and label site are three separate gates.
Other names the Core still tests
Avicides and piscicides appear on some labels and in federal competency language; they are uncommon in most New Jersey commercial routes, but they are still pesticides and still require a matching category and label. Termiticides are insecticides with extra New Jersey use restrictions in N.J.A.C. 7:30-10.4. Baits are a formulation (next section) sitting on top of an insecticide or rodenticide type. Do not confuse the type (what organism it is for) with the formulation (how it is packaged and mixed).
Contact versus systemic
Contact pesticides kill or injure when the pest, or the plant surface the pest must walk or feed on, is directly treated. They do not reliably move inside the plant or animal. Coverage and timing matter. A contact insecticide missed under a leaf, inside a gallery, or in a closed bud does not “soak in later.” A contact herbicide (a burndown) kills green tissue it wets; it will not clean up roots it never reaches if the label and the biology require translocation.
Systemic pesticides are absorbed and translocated. In plants they may move in xylem, phloem, or both. In animals, some parasiticides and some baits act after ingestion and internal distribution. Systemics can reach cryptic feeders, new growth, and roots — and they can leave residues in nectar, pollen, fruit, meat, or milk that a contact spray would not. That is why preharvest intervals (PHI), grazing restrictions, and pollinator statements are not optional fine print on systemic products.
A third working idea is stomach poison: the pest must eat treated tissue or bait. Many rodenticides and many insect baits work this way. A German cockroach that never feeds on the bait placement is not controlled by a “systemic” story you invented. Insect growth regulators (IGRs) and some chitin-synthesis inhibitors do not knock adults down on contact; they disrupt molting or reproduction. Customers who want dead insects in ten minutes will call that a failure. It is a mode-of-action mismatch, not a bad batch.
Translaminar products sit between contact and fully systemic: they move through a leaf blade but do not travel the whole plant. Read the label’s movement language. Do not treat “it is a liquid” as “it is systemic.”
How that choice fails in the field
A Category 3A crew sprays a contact miticide on the top of holly leaves for spruce spider mite. Mites live on the underside. Contact product plus incomplete coverage equals a callback. A 3B crew uses a contact burndown on yellow nutsedge and wonders why tubers return; many nutsedge labels require a systemic herbicide and a specified growth stage. A 7A operator uses a contact aerosol on bed bugs in a void he cannot see; a dust, a crack-and-crevice residual, or a different method the label allows would have been the coverage choice. 40 CFR 171.103(c)(5)(v) calls these “factors that influence effectiveness.” The Core writes them as contact versus systemic items.
Selective versus nonselective
Selective pesticides control some species and spare others at the labeled rate, timing, and site. 2,4-D and similar auxin herbicides can take broadleaf weeds out of a cool-season lawn if the turf species is on the label. Bacillus thuringiensis (Bt) is selective for certain caterpillars. A narrow-spectrum insecticide may spare predatory mites that a broad-spectrum pyrethroid will not.
Nonselective pesticides affect a wide range of plants or pests. Glyphosate on a mixed stand, a soil fumigant, or a broadcast pyrethroid in a restaurant kitchen (if the label even allows that site) are nonselective in practical effect. Nonselective is not a license to ignore the label. Glyphosate still has sites, rates, and aquatic-use limits. A “weed killer” jug from a hardware aisle is still a pesticide under N.J.A.C. 7:30 when a commercial applicator uses it for hire.
Selectivity is rate- and stage-dependent. Too much selective herbicide, or the wrong temperature, becomes nonselective injury — phytotoxicity. Too little becomes a resistance and callback factory. The Core pairs this with animal and plant toxicity of formulations in 40 CFR 171.103(c)(5)(iii); the next section covers formulation-driven phytotoxicity, but the type decision starts here.
Category trap: killing every plant on a right-of-way, industrial yard, dam face, or runway is 6A or 6B vegetation management, not “just 3B with a hotter mix.” 3B is turf pest control. If the site is not turf you are maintaining as turf, stop and check the category before you check the nozzle.
Mode of action and IRAC, HRAC, and FRAC groups
Mode of action is the biochemical or physiological process the product disrupts — a nerve-axon sodium channel, an EPSPS enzyme, a fungal respiration complex, a molting hormone receptor. Chemical family (pyrethroid, neonicotinoid, triazine, strobilurin) is related but not identical. Two families can share a mode of action; two products in one family almost always do.
Labels and technical sheets print group numbers:
- IRAC for insecticides and miticides.
- HRAC (and the related WSSA group numbers) for herbicides.
- FRAC for fungicides.
You do not memorize every group number for PACER. You read the group on the label and treat it as the resistance unit. 40 CFR 171.103(c)(5)(v) explicitly names pesticide resistance as a Core problem. Resistance is a heritable pest trait: the survivors of a mode of action become a larger share of the population. Repeating the same group — even with a new brand, a new tank mix partner that is only a synergist, or a “different” pyrethroid — selects for that trait.
Resistance management that the Core expects you to describe:
- Identify the pest and confirm the label lists it (40 CFR 171.103(c)(4)).
- Use the product only when a threshold or inspection justifies it (IPM; Chapter 11).
- Rotate modes of action across generations or seasons, not merely rotate distributors.
- Stay inside the labeled rate. Cutting the rate to “save mix” is a resistance and a 7:30-10.2(a) problem.
- Pair chemical tactics with nonchemical tactics so the pesticide is not the only pressure.
- For herbicides, do not rely forever on one HRAC group on the same New Jersey turf or right-of-way.
- For fungicides, do not spray a single FRAC group on a golf green every week just because the last spray “worked.”
Synergists such as piperonyl butoxide (PBO) can increase the effect of some insecticides. They are still not a new IRAC group. Adding PBO does not convert two Group 3A pyrethroids into a rotation.
Worked New Jersey scenarios
Scenario A — wrong type. A 7A customer in Newark reports “bugs and mushrooms” in a damp basement. The operator applies a household insecticide to the fruiting bodies. The organisms are fungi. The labeled tool, if any chemical is warranted, is a fungicide or an antimicrobial on a labeled site, plus moisture correction. Spraying an insecticide at a fungus is ineffective use under 40 CFR 171.103(c)(5)(v) and may be inconsistent with labeling.
Scenario B — contact on a systemic problem. A Burlington County 3A account has scale insects on euonymus. The crawler stage is over. A contact pyrethroid wets the leaves and misses the armored covers. A labeled systemic or a crawler-timed contact would have matched the biology. The brand was not the error; the mode of movement was.
Scenario C — 3B versus 6A. A crew with only 3B is asked to brown-out vegetation along an industrial fence line and a paved equipment yard in Middlesex County. That is nonselective vegetation management, not turf. Category 6A is the matching New Jersey category. Using a 3B license and a lawn product off-site is a category and a label problem.
Scenario D — fake rotation. A mosquito contractor rotates Product A and Product B because the labels look different. Both list IRAC Group 3A. That is not a mode-of-action rotation. Resistance pressure continues.
Scenario E — rodenticide type plus New Jersey bait rule. A 7A rodent job uses a labeled rodenticide bait. Type is correct. N.J.A.C. 7:30-10.3 still requires tamper-resistant bait boxes or locations not accessible to children, pets, domestic animals, or non-target wildlife, with brand, EPA Registration Number, active-ingredient name and percentage, and signal word on the box. Choosing the right type does not waive the baiting rule.
High-yield traps
- Type (insecticide, herbicide, fungicide, rodenticide) is not the same as formulation (EC, WP, bait) and not the same as New Jersey category.
- Contact coverage failures look like “the product does not work.”
- Systemic products create residue, PHI, and pollinator questions that contact products may not.
- Selective at the labeled turf rate can be nonselective injury at a higher rate or on the wrong species.
- Industrial, runway, and dam vegetation control is 6A, not 3B.
- Same IRAC / HRAC / FRAC group means the same mode of action, regardless of brand.
Official resources
Two insecticides used on a New Jersey 8B mosquito route have different brand names but the same IRAC group number. What is the resistance implication under 40 CFR 171.103(c)(5)(v)?
A contact insecticide is the wrong match for which New Jersey situation?
A crew certified only in Category 3B is asked to kill all vegetation on an airport runway and an industrial equipment yard. Which statement is correct?