Farm pesticides: choose the crop, pest and treatment method

Farm chemicals and agri chemicals (agric chemicals): commercial herbicide and agricultural pesticide types

Herbicides kill weeds and other plants that grow where they are not wanted; insecticides kill insects and other arthropods; fungicides kill fungi. Pesticide is the wider term: it applies to all the substances used to control pests.

A pesticide label defines who may use the product and where, how, how much and how often. Every label carries the statement: "It is a violation of Federal law to use this product in a manner inconsistent with its labeling."

Match the pest to the pesticide category

Weeds are controlled with herbicides, fungi with fungicides, snails and slugs with molluscicides, and nematodes (microscopic, worm-like organisms that feed on plant roots) with nematicides.

Pesticide classes by function: pest-function categories

Plant growth regulators alter the expected growth, flowering or reproduction rate of plants; fertilizers are not included. Attractants lure pests to a trap or bait. Pheromones disrupt the mating behavior of insects.

How a commercial herbicide is classified

Penn State classifies herbicides in four pairs of terms. Pre-emergence herbicides are soil active, are applied before emergence and act on weeds as they germinate; they do not control established vegetation. Post-emergence herbicides control weeds after they emerge and can be foliar and/or soil active.

A selective herbicide is active only on certain vegetation, so it controls one type of plant without harming another. A non-selective herbicide injures all vegetation. Whether a herbicide is selective is often dependent on application rate, and a non-selective herbicide can be applied selectively.

Contact herbicides injure only the portion of the plant they touch and tend to act faster, with an immediate "knock-down" of the weed. Systemic herbicides are taken up by the plant, often interfere with its development by mimicking plant hormones, and can take longer to act but work throughout the plant.

Distinguish the ingredient from the formulation

The formulation of an herbicide is the material it is carried in or on, and its concentration in that carrier. Every herbicide product is a combination of active ingredients and inert ingredients, and the same herbicide can be available in more than one formulation.

Formulations are classified first as liquid or dry. All liquids are applied through sprayers or spot applicators. Dry products can be diluted in water and applied as a spray, or applied directly as granules or pellets.

Soluble powders, wettable powders, water dispersible granules, dry flowables and extruded pastes are mixed with water; granules and pellets are applied dry. Most dry products mixed in water form suspensions, in which the product is not dissolved by the liquid.

Flowable and aqueous suspension liquids settle out if not continuously agitated, and enough particles can settle to clog the sprayer. Unless the label says otherwise, liquid formulations should be protected from freezing, and liquids have a shorter shelf life than dry products.

Biological categories and biotechnology pesticides

Biopesticides derive from certain natural materials. Their major classes are biochemical pesticides, microbial pesticides and plant-incorporated protectants. Microbial pesticides consist of a microorganism as the active ingredient: a bacterium, fungus, virus or protozoan. Plant-incorporated protectants are pesticidal substances that plants produce from genetic material that has been added to them.

The target insect species of a Bt product depend on whether its protein can bind to a larval gut receptor, causing the larvae to starve.

Pesticide categories and inert ingredients

Conventional pesticides, antimicrobial pesticides and biopesticides are pesticide categories. Antimicrobial pesticides destroy or suppress harmful microorganisms on inanimate objects and surfaces.

Inert ingredients are the formulation components combined with active ingredients to make a pesticide product. They can prevent caking or foaming, extend shelf-life or protect the pesticide from degradation by sunlight.

Agri fungicide: common fungicides and the list of fungicides used in agriculture

An agri fungicide is a pesticide that kills fungi. Common fungicides used in agriculture include the systemic fungicides azoxystrobin, carboxin and mefenoxam, which are used for seed treatment. The seed treatment guide explains which of them target which pathogen, and the grape powdery mildew page covers fungicides in a vineyard.

Most commonly used pesticides in agriculture and the farming chemicals list

The three main groups on a farming chemicals list are herbicides for weeds, insecticides for insects and fungicides for fungi; pesticide is the wider term for all of them. Agricultural agro chemicals and farm agro chemicals also include fertilizers, which are not pesticides; see crop fertilizer selection. Which products are the most common or most popular depends on the crop and the state, so the products for your crop come from your state's extension guide and the labels.

Counted by pounds of active ingredient used on farms, glyphosate was the most used active ingredient in 2012 (270 million to 290 million pounds), as it has been since 2001; atrazine was second and S-metolachlor third. Twelve of the 25 most used active ingredients were herbicides, four fungicides, two insecticides, five fumigants and two plant growth regulators. The ranking counts pounds applied, not acres treated, so a product that is absent from it can still be important for your crop.

Pesticides for vertical farming and other indoor growing

The label names where a product may be used, so for a vertical farm or any other indoor growing space look for indoor or greenhouse use on the label itself. Some products are limited to exactly that: one EPA-registered insecticide is labeled "For greenhouse or indoor uses only." A product whose label names only field crops does not cover an indoor farm, because the label states that it is a violation of federal law to use the product in a manner inconsistent with its labeling. Ask the supplier which indoor sites and crops the label lists, and keep that page of the label with your records.

Dangerous pesticides used in agriculture

Some of the chemicals farmers use for crop treatment are hazardous to the person who handles them, so read the label of each product first: it defines who may use the pesticide and where, how, how much and how often. The pesticide label guide explains how to read them.

Systemic and contact pesticides

Pesticides can be absorbed by plants through the leaves and roots and move to other parts of the plant. Systemic insecticides move throughout the plant and can kill insects that feed on it. This type of insecticide can be harmful to bees and other pollinators, because a bee pollinating the plant may receive a toxic dose.

Selectivity and resistance

Broad-spectrum pesticides are more likely than pesticides designed for a specific pest to affect non-target organisms. Insects, weeds and diseases can become resistant to pesticides that are used repeatedly, so a pesticide is used only when necessary and only as often as the label indicates.

Treatments aimed at a particular life stage

Ovicides kill eggs of insects and mites. Insect growth regulators disrupt the molting, the maturing from pupal stage to adult, or other life processes of insects. Miticides, also called acaricides, kill mites that feed on plants and animals. Rodenticides control mice and other rodents.

Algicides kill algae in lakes, canals, swimming pools, water tanks and other sites.

Defoliants, desiccants and plant development

Defoliants cause leaves or foliage to drop from a plant, usually to facilitate harvest. Desiccants promote drying of living tissues, such as unwanted plant tops.

Choose farm pesticides from the crop, pest and proposed use

Pest abundance and the action threshold

Before taking any pest control action, IPM sets an action threshold: a point at which pest populations or environmental conditions indicate that pest control action must be taken. Sighting a single pest does not always mean control is needed.

Not all insects, weeds and other living organisms require control; many are innocuous and some are beneficial. Monitoring and accurate identification remove the possibility that pesticides are used when they are not really needed or that the wrong kind of pesticide is used.

Before asking anyone for a product, write down what the problem is: the crop, the pest you see, where in the field and how much damage. If you are unsure of the identification, ask the local crop adviser or Extension service before comparing brands. Keep a short record of each scouting visit: what you saw, the threshold you used and what you decided.

Prevention and control options

Prevention is the first line of pest control. In an agricultural crop it means cultural methods such as rotating between different crops, selecting pest-resistant varieties and planting pest-free rootstock.

When monitoring, identification and action thresholds show that control is required and prevention is no longer effective, effective, less risky controls are chosen first, including highly targeted chemicals such as pheromones to disrupt pest mating, or mechanical control such as trapping or weeding. If these do not work, additional methods such as targeted spraying of pesticides are used. Broadcast spraying of non-specific pesticides is a last resort.

Use these steps to ask whether the present problem calls for a chemical purchase, a different management action or just more observation.

What the label fixes for the product

EPA evaluates the data and ensures that the label translates the results into conditions, directions and precautions that define who may use a pesticide, as well as where, how, how much, and how often it may be used.

Get the actual label of the exact product, read the general directions together with the subsection for your crop, and ask the adviser about any term you do not know. Keep the method you plan to use next to the label while you check it.

If the field was treated before, tell the adviser what was used and when, and ask about the mode of action of the next product: switching brands does not help if the new product works the same way.

Natural and environmentally friendly products

Natural and biological pesticides fall in the biopesticide classes described above; EPA states that biopesticides derive from certain natural materials such as animals, plants, bacteria and certain minerals. Systemic products of any origin can move through the plant and reach pollinators, so the "Environmental Hazards" section of the label applies to them.

If you plan a systemic product, check the flowering stage of the crop and the habitat next to the field, and read the pollinator directions on the label before you buy.

Soil-applied pesticides: distinguish the target, crop and method

Soil can be degraded and the community of organisms living in it damaged by the misuse or overuse of pesticides. Some pesticides persist in soil longer than others, and the type of soil and the type of pesticide both affect persistence.

Check the soil type, drainage and any water close to the field, and read the product's environmental information with those conditions in mind. Treat two questions separately: whether the product persists or leaches at your site, and whether it controls the target without hurting the crop.

What a soil treatment targets

Nematicides kill nematodes and fungicides kill fungi; a below-ground target is one or the other, and each has its own pesticide category.

Soil type and leaching

Pesticides applied to sandy or coarse-grained soils are more likely to leach through the soil and contaminate groundwater.

How the material reaches the target

Pesticides in soil may be taken up by plant roots and moved to other plant tissues, including the fruit. Herbicides applied to the soil are absorbed by roots in the treated area.

Fumigation

EPA requires a suite of complementary safety measures to protect handlers, reentry workers and bystanders from soil fumigants, focused on acute human inhalation risks. Most apply to all soil fumigants, for example fumigant management plans; some are specific to individual fumigants, for example buffer distances. See also fumigant selection.

Treat fumigation as a specialist job. Give the fumigation contractor the exact product, the site and the method you intend, and ask to see the site-specific plan, buffers, handler protection and emergency arrangements before work starts.

The size of a buffer zone around a treated field is based on application rate, field size, application equipment and methods, and emission-control measures such as tarps. Buffer zone distances are given in look-up tables on product labels.

Buffer zones must be posted at usual points of entry and along likely routes of approach unless a physical barrier prevents access. The signs must include a "do not walk" symbol, the fumigant product name, and contact information for the fumigator.

Handlers must be fit-tested for respirators, trained in how to use a respirator, and determined to be healthy enough to wear it.

Agriculture insecticide or herbicide for the target

Insecticides kill insects and other arthropods; herbicides kill weeds.

When you buy, name the crop and the diagnosed target first, and only then compare products. For a soil treatment, name the below-ground target and ask what application method the label permits.

Pesticide efficacy testing

Before commissioning a test, agree with the specialist on the target pest, the treatment, the comparison, the observation dates and how damage or control will be measured. Keep the product directions and the field history with the plan. Ask how the observations will tell treatment performance apart from missed coverage or a change in the pest population.

Next step

See nonchemical crop protection and how to read a product label.