Understanding Common House and Garden Insecticides

Pesticides include any substances used to kill, control or repel pests. We use pesticides almost every day, from ant and roach sprays for the kitchen, to weed killers for the lawn, mildew cleaners for the bathroom and mosquito repellents outdoors. Pesticides have become a widely accepted way to keep our homes and gardens relatively pest-free. About 85% of all American households keep at least one pesticide in storage.

Despite our willingness to use them, most consumers associate pesticides with pollution, health risks and toxic chemicals. Surveys show that about 75% of consumers are wary of using pesticides in the home. Many people today are avoiding certain synthetic (man-made) pesticides in favor of natural or “organic” products. But regardless of whether a substance comes from natural or artificial sources, if it controls pests, it’s a pesticide. And as long as pests are around, chances are that we will use pesticides.

There are many types of pesticides. Insecticides are pesticides designed to control insects. Herbicides are pesticides designed to kill weeds. There are dozens of others. In this f@ctsheet we will learn about the different kinds of insecticides and how to choose the right one for the job.

Choosing the right formulation

The first decision to make when selecting a pesticide is what formulation to use. A formulation is the way the pesticide active ingredient is mixed with inert ingredients to make it convenient and effective to use. Factors that influence the choice of formulation include cost, convenience in mixing and use, effectiveness against your target pest and safety. The following table describes the most important types of insecticide formulations and how they should be used.

Table 1. Various types and uses of insecticide formulations.
Type Description Where and how to use Relative Safety Cost

Dust

An insecticide active ingredient is sprayed onto a finely ground dust.

Dusts are best used to deliver an insecticide to difficult-to-reach areas. Common uses include treatment of ants in a wall, or wasps in the ground. Ants and other social insects will track the applied dust deeper into a nest. Dusts are often sold for garden use, but application there is inefficient and much of the insecticide is likely to be blown or washed off the intended target. Best to apply with a crank duster or squeeze bottle designed for applying dusts.

Low to moderate. Easy to inhale, may drift from the intended target site.

Low

Granular

Insecticide is sprayed onto an inert, absorptive granule; usually consisting of clay, ground corn cob, or nut husks.

Granular insecticides are designed to provide control of soil dwelling insects. They are less effective against surface crawling pests, unless these also spend much time underground in the treatment zone. Commonly used for control of ants, grubs, millipedes, etc. Easy to apply with a rotary, drop, or hand-held seed spreader.

High. Because insecticide is impregnated inside an inert carrier, spills are easily contained and little exposure risk to exposed skin.

Low

Aerosol

Insecticide mixed with gas in a metal can. Can be designed to produce a various particle sizes from fine aerosol to liquid stream.

Easy to use and apply, designed for application of residual sprays for crawling insects as well as for aerosol fogs for flying insects, depending on product. Commonly sold for ant and roach control, or flying insect control. Despite the impression given by advertisements, aerosol fogs do not penetrate well into cracks and crevices where pests hide.

Low to moderate. Some formulations are flammable. Solvents may add to toxicity, and exposure risk to skin is higher. Empty cans should be wrapped in newspaper for disposal to prevent accidental punctures.

High

Baits

Consist of an insecticide mixed with a food or attractant to entice the insect to ingest. Come in various forms including pellets, dusts, gels, liquids and granules.

One of the most effective control methods for controlling social insects, like ants and termites. Also very effective on cockroaches and crickets. Various ways to apply.

High safety due to the low percentage active ingredient needed to produce control. Containerized baits are exceptionally safe. Broadcast treatments of low rates is generally the safest application method.

Low to moderate

Spray – Ready to Use (RTU)

Premixed liquid, usually in a pump spray bottle or as a hose-end attachment.

Designed for convenience, RTU sprays require the user to just point and pump or attach to a garden hose. No mixing required. Usually designed for tree, lawn and garden sprays, flea sprays.

Moderate. Because there is no mixing, risk of your exposure to the concentrate is eliminated. User should avoid exposure to spray drift by using gloves and long-sleeves.

Moderate to high

Spray – Concentrate

Concentrated active ingredient in an emulsion or solution. Designed to be mixed with water before application.

Wide range of uses include both indoor and outdoor sprays, lawn and garden sprays and soil drenches.

Higher risk because of need to mix concentrated product and potential for exposure to spillage, drift or splashing.

Low

Common types of pesticides

One way to think of pesticides is as low-impact or as conventional. Low impact products include those that are low in toxicity to people and pets (i.e., meets EPA Category IV standards) and have minimal impact on the environment, including beneficial insects. This classification is somewhat subjective, but still provides a useful way to select pesticides that meet most people’s definition of green or safer.  Some, but not all, low-impact pesticides may be classified as “organic.” Some organic products may not be considered low-impact if they are highly toxic. Here are a few examples of common low-impact insecticides that are widely available in hardware stores and garden centers.

Table 2. Classification of low impact insecticides, with examples.

Type Common Name Examples (Trade names) Pests
Insect Growth Regulators halofenozide Scott’s Grub-Ex, Ortho Grub-B-Gone, Mach 2 white grubs
methoprene Precor, vIGRen, Extinguish, others fleas, fire ants
pyriproxifen Nylar, Spectracide fire ant bait, others fleas, fire ants
Microbially-derived Bacillus thuringiensis Dipel, Thuricide, Mosquito Dunks, others caterpillars, mosquitoes
spinosad Fertilome Bagworm and Tent Caterpillar spray, others caterpillars, thrips, fire ants
Contact insecticides (kill only when sprayed directly on the pest) soap Safer’s Soap, others small, soft-bodied pests (aphids, mites, caterpillars, mealybugs)
horticultural oil GreenLight Dormant Oil, Sunspray, Neem oil, Rose Defense, others small, soft-bodied pests (aphids, mites, caterpillars, mealybugs, scale insects)
Botanical (plant derived products) pyrethrum, synergized pyrethrins Raid Flying Insect Killer, Schulz’s Plant Spray, many others quick acting killer for many garden and house plant pests, flying and crawling insects
d-limonene Citrus oil spray, Citrex, others fire ants, others
azadirachtin Neem concentrate, others aphids, whiteflies, spider mites, scale insects, others
Baits hydramethylnon Amdro, MaxForce, others fire ants, cockroaches, other ants
sulfluramid Combat Roach Killing Gel, Raid Ant Bait ants, cockroaches
Low toxicity inorganics sulfur dusting sulfur, various brands mites, chiggers
boric acid and derivatives Roach Pruf, Boracare, various baits roaches, ants, termites, other crawling indoor pests
diatomaceous earth DE, various brands of diatomaceous earth crawling insects, fleas, indoor pests only

Conventional insecticides include pesticides that are not considered low-impact because they are more likely to be hazardous to humans or pets (without careful attention to standard safety practices and following the label), or because they may impact beneficial insects or the environment even when used according to the label. Most of the products listed below have the potential to harm at least some beneficial insects and for this reason should be used when cost-effective, low-impact products will not adequately control the pest.

Just because a product carries the potential for harm, does not mean it cannot be used safely. Conventional pesticides include many useful and effective products that can be used safely by most gardeners. However, it is especially important to follow label safety directions when using conventional pesticides. Here are some of the common types of conventional insecticides.

Table 3. Classification of conventional insecticides, with examples.

Type Common Name Examples (Trade names) Pests
Systemics (water-soluble insecticides that can be taken up by plants) acephate Orthene, others chewing and sucking insects, mites and lacebugs
imidacloprid Bayer Advanced Garden products sucking insects, beetle larvae, white grubs
dinotefuran Spectracide Systemic Tree and Shrub Insect Control + Fertilizer sucking insects including armored scale, beetle larvae, some borers
disyston Bayer Advanced Garden Rose Insect Killer Granules sucking and chewing insects (moderate-high toxicity)
Pyrethroids permethrin Conquest, Spectracide, others sprays and granules for chewing and crawling insects, borers
resmethrin, allethrin Wasp and Hornet spray, others short residual sprays for flying insects, spiders, household insects, mosquitoes
esfenvalerate, cyfluthrin, bifenthrin, deltamethrin, lambda-cyhalothrin, tralomethrin, cypermethrin, others Ortho Home Defense, Bayer Advanced Garden, Zep, others… these newer pyrethroids generally provide longer residual and higher activity on chewing and crawling insects
Other residual insecticides (leave a killing residue on surfaces) carbaryl Garden Tech Sevin, others chewing and crawling insects, slugs, snails
malathion Malathion, others short-lived residual treatment for a variety of chewing, crawling insects, mosquitoes
fipronil Over N Out, MaxForce ant baits, others long-residual granular product for fire ant control, termites, general treatment for crawling insects, especially ants

Organic vs. Synthetic pesticides

In recent years a growing number of pesticide products advertised as “organic” have become available to consumers. To be considered organic a pesticide must be composed of only naturally occurring substances. Advertizers and others commonly imply that organic pesticides are safer and more environmentally desireable than synthetic products. While this may be true in some cases, there is no guarantee that natural substances are inherently safer than synthetic pesticides.

Organic pesticides usually consist of plant extracts with insect-killing or repelling properties. Plants produce many chemical compounds to protect themselves from diseases, insects and other threats. From a toxicology perspective, there is no difference between plant-derived pest control compounds and man-made pesticides. Both are chemicals. Both have some effect on the physical structure, development or metabolism of insects. And both organic and synthetic pesticides can be toxic to humans.

Most commonly sold “organic” insecticides, however, are reasonably low in toxicity and break down quickly upon exposure to water and sunlight. Their ability to degrade quickly and their relatively low toxicity is why botanical insecticides are usually classified as low-impact. However, there are exceptions. Rotenone, for example, is a popular insecticide with many gardeners because it is organic, effective in controlling many chewing pests and does not leave long-lasting residues on plants. In its concentrated form, however, rotenone is more toxic than many conventional insecticide active ingredients.

Don’t be misled by sales claims for many so-called “natural” products. Advertising which claims that any insecticide is “safe”, “pure”, “all-natural”, “EPA-approved”, “pesticide-free” and “chemical free” are at best misleading; and at worst, false and/or illegal. Many people get great satisfaction from using only substances found in nature in their garden. This is generally a good thing. However, use of synthetic pesticides can also be a safe and environmentally sound practice if practiced with care and discretion.

For more information

For more extensive information about the toxicology and safe use of pesticides visit the EPA-funded, National Pesticide Information Center at http://npic.orst.edu

Author:

Michael Merchant, Ph.D., Professor and Extension Urban Entomologist, Texas AgriLife Extension Center at Dallas

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