5.2 Biological, Mechanical, Cultural, and Chemical Control

Natural controls versus applied controls

National Core Manual Chapter 1 splits pest suppression into forces that operate whether or not you show up, and tactics people apply on purpose.

Natural controls check pests without depending on humans for their continuance: climate (a freeze that cuts a pest flight, a wet week that favors pecan scab), natural enemies, topographic features, and the supply of food and water. Georgia already runs on natural controls. A hot, dry cotton bloom can slow some foliar diseases and explode mites. A coastal drought can shrink mosquito larval sites — or concentrate them in the ditches that still hold water. You do not "turn off" climate. You account for it when you decide whether an applied tactic is even justified.

Applied controls are the methods humans add. Chapter 1 lists seven, and the exam expects you to name them and give a field example, not to treat the list as poetry:

1. Biological control
2. Mechanical control (cultivation, exclusion, trapping)
3. Cultural control (cultural practices and sanitation)
4. Physical / environmental modification
5. Host resistance or genetic control
6. Chemical control
7. Regulatory pest control (quarantine, inspection, eradication)

Rule 40-21-3's pests domain is recognition, damage, and biology as relevant to problem identification and control. This section is the control half. Resistance as a pesticide-use problem is Domain 5 and Section 5.3; here the trap is narrower and just as deadly: chemical control is one applied method, not the definition of pest control.

Biological, mechanical, cultural, and physical methods

Biological control uses living organisms: predators, parasitoids, pathogens, and antagonists. Conserving lady beetles and lacewings in a pecan orchard is biological control. Releasing or conserving parasitoid wasps that attack caterpillars is biological control. A Bacillus thuringiensis (Bt) spray that the pest must ingest is a microbial insecticide — biological in origin, applied like a pesticide, still not "spray any insecticide." Destroying those beneficials with an unneeded broad-spectrum pass is how secondary mites appear in cotton. Biological control is not wishful thinking that "nature will handle Palmer amaranth in a seed bank the size of a peanut hopper."

Mechanical control uses devices, tools, or machines. Cultivation buries or uproots weeds in cotton and peanuts — and can also move perennial rhizomes if you disk johnsongrass thoughtlessly. Exclusion is screens, row covers, sealed storage, or mosquito-proofing a rain barrel. Trapping includes pecan weevil traps that time adult emergence, mosquito traps used in surveillance, and sticky or light traps that monitor rather than replace a program. Mowing a right-of-way is mechanical suppression of height; it is not eradication of kudzu crowns. Hand-pulling a few winter annuals around a peach trunk is mechanical. A boom sprayer is chemical application equipment, not mechanical pest control in the Chapter 1 sense.

Cultural control changes the environment, the host, or pest behavior through how you grow or maintain the site. Georgia examples that belong in your notes:

• Crop rotation and row spacing in cotton and peanuts to break weed, nematode, and some insect cycles
• Planting date and in-furrow/at-plant decisions that reduce TSWV pressure in peanuts (thrips and virus risk are not solved by a July rescue fungicide)
• Sanitation: peach mummy fruit left in the tree or on the ground feeds brown rot; pecan shucks and sticktights harbor insects and inoculum; dumping clippings that are full of seed on a clean turf stand is anti-sanitation
• Irrigation and fertility that either favor turf disease (night-long wet putting surfaces) or keep a crop competitive with weeds
• Mowing height on turf and mowing schedule on rights-of-way as a cultural/mechanical overlap that changes weed and insect habitat

Physical / environmental modification changes temperature, humidity, light, or water in a more engineered way than ordinary cultural practice: cold storage of commodities, heat or steam for some nursery or greenhouse media, flooding or draining a site, black plastic or other mulches that change soil temperature and light, indoor humidity control, and source reduction that dumps container water so mosquito larvae have no habitat. Coastal Category 41 work that dumps tires and gutters is physical/cultural source reduction. It is not an adult fogger, and the Core Manual will not let you call it chemical control.

Host resistance, chemical control, and regulatory control

Host resistance or genetic control is a plant (or animal) that withstands a pest because of breeding or biotechnology. It is not a spray. Georgia's working picture:

• Bt cotton expresses Bacillus thuringiensis proteins in plant tissue. Caterpillars that ingest those proteins are the target. That is genetic/host resistance. It is not the same decision as applying a foliar insecticide, and it does not retire scouting. Plant bugs, stink bugs, and mites do not read the Bt trait as a force field.
• TSWV-tolerant or resistant peanut cultivars are genetic tools against a virus you cannot fungicide away.
• Pecan and peach cultivar and rootstock choices change scab, bacterial spot, or nematode pressure.
• Turfgrass cultivars differ in chinch bug, grub, and disease tolerance — the difference between an aesthetic threshold you can live with and a lawn you will spray monthly.

Do not call a Bt crop "chemical control" on the exam. Do not call a resistant peanut "regulatory control." Section 5.3 covers resistance management for both sprayed modes of action and Bt traits (refuges, rotation). This section only places host resistance on the methods list.

Chemical control uses pesticides: insecticides, miticides, herbicides, fungicides, nematicides, rodenticides, and the rest of the labeled toolbox. Chapter 1 still expects the distinctions you will meet again in the formulations chapter: selective versus broad-spectrum, contact versus systemic, protectant versus curative fungicides, residual versus short-lived. Chemical control is legal only when the label allows the site, pest, rate, and method — FIFRA and Georgia use law sit in earlier chapters. The pests-domain point is narrower: chemicals are for a named pest at a susceptible stage when other methods and thresholds say they are needed. A right-of-way crew treating woody brush, a Category 24 lawn firm treating grubs, and a Category 21 custom applicator treating peanut leaf spot are all using chemical control. None of them is excused from identification.

Regulatory pest control is a government method, not a tank-mix. It includes quarantine (stop movement of infested plants, soil, fruit, or equipment), inspection, and eradication (area-wide removal of a pest). Georgia cotton's boll weevil eradication is the example every Core Manual student should be able to cite: a coordinated regulatory program, not a grower deciding to "spray harder." USDA APHIS and the Georgia Department of Agriculture still use quarantines and hold orders when an exotic pest or a regulated article shows up. Category 32 (Regulatory) is the government applicator category for that work; your Category 21 card does not turn you into a quarantine officer. Regulatory control is an applied pest-management method on the exam. Treat it that way.

Put the seven methods in one sentence you can reproduce under the 2.5-hour clock: identify the pest, then pick from biological, mechanical, cultural, physical, genetic, chemical, and regulatory tools — chemical last when it is last, not because the truck is already loaded.