9.1 Pest Identification and Biology

The Oklahoma Department of Agriculture, Food, and Forestry (ODAFF) Core examination tests the federal commercial-applicator pest competency in 40 CFR 171.103(c)(4). That paragraph is titled Pests. Written Core exams must address proper identification and effective control of pests, including two duties National Core training repeats until they are automatic. Under (c)(4)(i), you must understand the importance of correctly identifying target pests and selecting the proper pesticide product(s) for effective pest control. Under (c)(4)(ii), you must verify that the labeling does not prohibit use of the product to control those target pests. Wheat in the northwest, cotton in the southwest, native pecan along river bottoms, Category 7A kitchens in Oklahoma City, Category 7B structures, Category 8 mosquito work, and pasture weed jobs all start with the same question: what organism is actually causing the problem?

This section is Core biology and identification, not a Category 7B termite pretreat manual, not a full public-health mosquito-district course, and not a cotton entomology degree. You still need enough life-cycle detail to refuse a jug, time a pass, and explain a failure.

What counts as a pest

A pest is an organism that interferes with a human goal: yield, forage quality, public health, stored food, a building, turf quality, or a landscape a client is paying to keep. Palmer amaranth in Tillman County cotton is a pest. A German cockroach in a Norman restaurant is a pest. A subterranean termite colony in a Stillwater crawlspace is a pest. House mice in a grain elevator are pests. Beneficial lady beetles, parasitic wasps, and predatory mites are not pests; they are doing work you would otherwise buy as a spray. Treating everything that crawls is how you create spider-mite flares, illegal uses, and resistance.

A plant is a pest when it is unwanted in that site. Johnsongrass in a bermudagrass pasture is a weed. The same biology in a sorghum relative on a right-of-way is still a vegetation-management problem, but the label decision is always site plus pest, never a moral judgment that a species is illegal everywhere.

Six organism groups Core expects you to separate

Core does not require you to be a taxonomist. It does require you to name the kind of organism so you pick the kind of pesticide (Chapter 5) and the right life-stage tactic.

Insects versus mites is a classic trap. Spider mites are not insects. If the speckling on cotton is mites, a leftover bollworm pyrethroid can erase predators and make the outbreak worse. Nematodes are not insects either; they live in soil and roots. Rodents are vertebrates. Dropping size, burrow versus climbing behavior, and grease marks tell Norway rat, roof rat, and house mouse apart; a 7A cockroach aerosol is not a rodenticide, and a rodent bait station is not a German cockroach program.

Complete versus incomplete metamorphosis

Metamorphosis is how an arthropod changes form as it grows. Timing a pesticide to the damaging and vulnerable stage depends on which pattern you are looking at.

Complete metamorphosis has four stages: egg, larva, pupa, adult. The larva does not look like the adult. Many agricultural and public-health insects use this pattern.

• Armyworms. True armyworm (Mythimna unipuncta, listed as Pseudaletia unipuncta on older Oklahoma State University sheets) and fall armyworm (Spodoptera frugiperda) damage wheat, pasture, sorghum, and turf as caterpillars. The moth is the adult. Young larvae skeletonize leaf surfaces; older larvae eat from the leaf edge and can strip a stand. OSU notes true armyworm invasions often start in lush or lodged grass and that turf damage is usually worst when the species is already abundant in wheat. A spray timed only to flying moths does not replace larval scouting in the canopy. Soap flushes on turf (a labeled dish-soap drench in a known square footage) tell you whether caterpillars are present before you treat.
• Bollworm and stink bug in cotton. Bollworm / corn earworm (Helicoverpa zea) is a chewing caterpillar in squares and bolls. Stink bugs (green, brown, and related species) are a different order with piercing-sucking mouthparts; they stain lint and open bolls to rot. One “cotton bug” story does not pick the product or the scouting method. Squares, damaged bolls, and drop-cloth or sweep counts are not interchangeable with a windshield survey from the turnrow.
• Pecan weevil (Curculio caryae). This snout beetle is the native-pecan insect Oklahoma growers plan a year around. OSU Extension describes a typical two- to three-year life cycle: larvae feed in the nut, drop to the soil (often several inches deep), and most adults emerge about two years later, with a fraction waiting until year three. Adults live on the order of two to three weeks. Feeding punctures before shell hardening can drop nuts; oviposition after dough stage puts eggs inside the kernel. Circle traps time adult emergence. Once eggs are in the nut, a foliar insecticide will not reach the larva. That is biology, not a weak brand.
• Mosquitoes (Category 8 public health). Stages are egg, larva (wriggler in water), pupa (tumbler), adult. Culex, Aedes, and Anopheles differ in where they lay eggs and which diseases they can move, but Core only needs the life-cycle logic: larvicides belong in standing water when larvae are the target; adulticides target flying adults. Dumping containers, grading ruts, and clearing clogged ditches change the larval habitat. This chapter does not certify you as a mosquito-control district; it stops you from fogging a dry parking lot and calling it larval control.

Incomplete (simple) metamorphosis has egg, nymph, and adult. There is no pupa. Nymphs look like smaller adults and often eat the same food in the same places.

• German cockroach (Blattella germanica), Category 7A. Adults are small, tan, with two dark stripes on the pronotum. Females carry an ootheca (egg case). Nymphs are the same pest as adults in a dish pit or break-room toaster. Incomplete metamorphosis is why a mosquito “larvicide” story does not transfer to cockroaches. You are treating a population of nymphs and adults in harborage, not waiting for a pupal stage that does not exist.
• Stink bugs on cotton: nymphs and adults both puncture fruiting structures, so a “only spray moths” habit imported from bollworm will miss the actual feeding stages.
• Subterranean termites — identification only on Core. Oklahoma structures commonly see Reticulitermes species. Workers are pale and stay in mud; soldiers have darkened heads and mandibles; reproductives (swarmers) have two pairs of equal-length wings that they shed. Shelter tubes of soil on slabs, crawlspace piers, and foam board are a sign of a soil-connected colony. Carpenter ants have a pinched waist and unequal wings; their frass is fibrous, not soil tubes. Drywood termites are a different biology and a different treatment family. Category 7B written work plus the OSU Stillwater practical covers soil pretreat, baiting systems, and structural modification. Do not treat this Core section as a pretreat how-to: depths, trenching, foam, and labeled termiticide volumes belong in 7B, not here.

Weed life cycles

Annuals finish a seed-to-seed cycle in one growing season and overwinter as seed. Palmer amaranth (Amaranthus palmeri) is Oklahoma’s exam-poster annual pigweed: long petioles, often dioecious (separate male and female plants), capable of rapid growth in heat, and capable of hundreds of thousands of seeds from a mature female. OSU weed programs treat Palmer and waterhemp as the pigweeds that break glyphosate programs in soybean and cotton. Confusing Palmer with a grass changes the herbicide family you reach for. Confusing it with a small seedling johnsongrass changes whether you are fighting an annual seed bank or a perennial rhizome system.

Biennials spend the first season as a rosette and flower in the second. Musk thistle in pasture is the usual picture. Cutting or spraying after seed is already moving is too late for that year’s contribution to the seed bank.

Perennials live more than two years and regrow from crowns, roots, or rhizomes. Johnsongrass (Sorghum halepense) is a perennial sorghum relative with a pale midrib and aggressive rhizomes. A contact burndown that burns tops and leaves rhizomes is a stall, not control. Seedlings can look like annual grass until the rhizome network is in place; that is when a systemic grass herbicide, competition, and preventing seed all matter together. Mowing seed heads before they mature reduces new seed; it does not excavate rhizomes.

The disease triangle

Infectious plant disease is not automatic when a spore is in the county. The disease triangle requires a susceptible host, a virulent pathogen, and a favorable environment at the same time. Remove one side and disease does not progress the same way. A peanut canopy that stays wet, a susceptible cultivar, and a leaf-spot fungus are a triangle. A turf stand scalped before a humid week is an environment side you created with a mower. Core uses the triangle to stop “fungicide first” thinking. Many viruses and some bacterial diseases are not cured by a leftover foliar fungicide labeled for a fungus. Nematode feeding can also open roots to pathogens; that still does not make a nematicide a fungicide.

Why mis-identification is illegal and ineffective

Wrong ID causes two Core failures at once.

Illegal use. The label is the law. If the pest is not on the label, or the label prohibits that pest or site, the application is inconsistent with the labeling. 40 CFR 171.103(c)(4)(ii) is the exam sentence: verify that the labeling does not prohibit the product against the target pest. A cotton insecticide that lists bollworm but not spider mites is not a mite product. A 7A crack-and-crevice aerosol labeled for cockroaches is not a termiticide. A pasture herbicide labeled for johnsongrass is not automatically labeled for Palmer amaranth in cotton. A mosquito adulticide labeled for outdoor adult mosquitoes is not a kitchen cockroach bait.

Failed control. Treating armyworm moths and missing larvae, spraying pecan weevil after larvae are in the kernel, burning johnsongrass tops while rhizomes rest, or fogging a restaurant while grease and cardboard remain, all look like “the pesticide failed.” Often the biology was wrong. Repeated failed sprays of the same site of action also select for resistance (Section 9.3).

Scouting, then thresholds

Scouting is a planned inspection you can repeat: the same field, orchard, turf stand, or account, with a method that produces a number—sweep net, drop cloth, square-foot counts, soap flush for turf caterpillars, circle traps for pecan weevil, sticky traps or visual counts for German cockroaches, larval dips for mosquito water, droppings and gnaw maps for rodents. Write the pest, the stage, the site, and the count. Memory is not a record.

An economic injury level is the pest density at which damage equals the cost of control. An economic threshold (often called an action threshold) is the density at which you act so the population does not reach that injury level. Turf, interiorscapes, and 7A accounts often use aesthetic or public-health action thresholds instead of soybean break-even math: one German cockroach in a food-handling account, or mosquito landing rates that trigger a city program, are still thresholds. The Core idea is the same: identify, count, compare to a threshold, then choose a tactic. Mixing a tank because the neighbor mixed one, or because leftover product is aging in the shed, skips the competency 40 CFR 171.103(c)(4) is testing.

After you know the pest, open the label. Confirm the site (cotton, kitchen, turf, standing water, pecan) and the pest name or grouping. If the pest is absent or prohibited, stop. That check is as much a legal step as personal protective equipment.