Crop Pests and Insect Control

What counts as an agricultural pest

In farming, a pest is any organism that cuts yield or quality enough to matter: insects and mites first, but also nematodes, slugs, birds and rodents. Diseases and weeds are often counted too, and FAO estimates that up to 40 percent of global crop production is lost to pests each year (FAO, June 2021). Weeds and diseases have their own guide hubs, so this one stays with crop insects and mites.

Crop pests do damage in three main ways. Chewing insects such as caterpillars and beetles eat leaves, stems, roots or fruit. Sucking insects such as aphids, whiteflies and psyllids drain sap and, often more seriously, spread plant viruses and bacteria. Borers and fruit flies feed inside the plant or fruit, where sprays struggle to reach them. Knowing which group you’re dealing with narrows the control options before you’ve even named the species.

10 examples of crop pests and their control

These ten turn up on farms almost everywhere. Control options are listed roughly in the order an agronomist would reach for them.

For more detail on single crops, start with telling aphids from mealybugs or the cotton bollworm life cycle.

Pest control for farms, step by step

Most extension services teach integrated pest management, or IPM. The US EPA’s IPM pages describe the same basic sequence we see working on well-run farms:

1. Prevent problems with rotation, resistant varieties, clean seed and transplants, and timing planting to dodge peak pest flights.
2. Scout regularly, using traps and a set walking pattern, and record counts for each block.
3. Act only when counts pass an economic threshold, the level at which control costs less than the damage you’d otherwise lose.
4. Choose the most selective option that works, so natural enemies survive to keep the next generation down.
5. Rotate insecticides by mode of action, using the IRAC classification, to slow resistance.

Scouting is where most farms cut corners, and it decides how well everything else works. Walk a zigzag or W pattern through each block so you don’t only check the edges, stop at the same number of points every time, and turn leaves over, because aphids, whiteflies and mites sit on the undersides. Sticky traps and pheromone traps show when a flight starts, which is your cue to look harder.

Our main guide to eco-friendly pest control methods for farms covers thresholds and biological control in more depth.

Natural methods, insecticides and fumigation

Natural pest control methods range from releasing beneficial insects and leaving flowering strips for them, to pheromone traps and mating disruption, trap crops, and botanical or microbial products such as neem oil and Bacillus thuringiensis (Bt). They work best as prevention and early on. Once a heavy infestation has built up, they rarely bring it down fast enough on their own. Our articles on biological pest control that works and how crop rotation controls pests give examples.

Synthetic insecticides still have a place, but repeated use of one chemical group breeds resistance, as growers have seen with fall armyworm and whiteflies. Fumigation is a separate tool. It is mostly used on stored grain and, in some crops, soil before planting. The fumigants are highly toxic gases, and in the US phosphine-producing grain fumigants are restricted-use pesticides that only certified applicators may buy and apply. Treat any offer of cheap fumigation with care.

Where satellite monitoring helps

Satellites can’t see an aphid. What they can show is where a crop is falling behind its neighbors, which tells a scout where to walk first on a large farm. Our AI farm advisory combines that crop health data with weather to give a pest, disease and weed risk for each field, with a probability and two control options, one organic and one chemical. The 91 reports for a 190-acre wheat, barley and alfalfa farm in Algeria included six high-risk pest warnings. A warning is a prompt to scout, and the decision to spray should still rest on what you find in the field.