Insecticides in the Home Landscape and Garden

Many insects in the landscape or garden and around the home can be tolerated or managed without resorting to insecticide applications.  However, in some situations and under certain circumstances insecticide use may be warranted.

To reduce our dependence on insecticides, use of chemical controls should be integrated with other tactics such as mechanical removal, sanitation, and biological control.  Further, it may be possible and even desirable to tolerate a few pests rather than strive to eliminate insects from the landscape or garden.

When insecticides are warranted carefully chose the least toxic alternative.  Apply at the proper time when the pest is most vulnerable (usually while the insects are still small and before damage has become severe) and when beneficial insects such as pollinator and natural enemies will be least affected (for example, avoid spraying plants that are in bloom).

Carefully read the product label when choosing an insecticide.  Look for instructions on how to apply the insecticide to the site or type of plant you intend to treat.  This is especially critical when choosing insecticides for the home vegetable garden or orchard.  Many outdoor insecticides are labeled for use on ornamentals but are prohibited for use on food crops.  Read and follow important label directions such as environmental and applicator hazards, plants and pests that can be treated, amount to apply, frequency of reapplication and how long you must wait before you harvest treated food crops.

Many familiar over-the-counter insecticides used in the home landscape and garden during the past several years have disappeared from the store shelves due to a variety of regulatory and marketing decisions.  Most recently among these was the disappearance of diazinon and chlorpyrifos (Dursban) from the over-the-counter market. Other familiar stand-bys such as acephate (e.g., Orthene), dimethoate (e.g., Cygon) and disulfoton (Di-Syston, and 2-in-1 Rose Systemic Granules) are slowly disappearing as existing products are sold off and not replaced.  The result is fewer choices for homeowners and home gardeners, or substitutions with newer products with which many are not as familiar.

See Table 1 below for a list of some insecticides available for use in the home landscape and garden. When using any pesticide product, always read and follow label directions.

Pyrethroid Insecticides

Many of the newer insecticides appearing as substitutes for older products are called pyrethroids.  These synthetic (i.e., manufactured) products are related to the naturally-occurring, botanical insecticide called pyrethrin.  Pyrethrin insecticides are extracted from the flowers of the pyrethrum chrysanthemum, grown for this purpose in several parts of the world.  Pyrethroids are similar in structure and function to pyrethrins.  Both are very effective against insects at very low doses and work very rapidly. For most uses, pyrethroids have the advantage of remaining effective for several days or weeks after application, whereas pyrethrins may remain effective for a few minutes at most.

Pyrethroid insecticides vary greatly in their toxicity, residual life and efficacy against pests.  However, as a group, they are less toxic than the organophosphates and carbamates products they have replaced.  Pyrethroids are considered broad-spectrum pesticides because most are active against a wide range insects (ants, cockroaches, fleas, true bugs, aphids, scales, beetles, caterpillars, flies, and wasps).  Because of their broad spectrum of activity, relatively low toxicity and availability, pyrethroids have been the insecticides of choice as replacements in over-the-counter products.

Several over-the-counter pyrethroid insecticides are listed in Table 1.

Table 1. Home Landscape and Garden Insecticides

More Information

• Herbicide Injury to Garden Plants
• Chemical Injury to Garden Plants
• Home and Garden Pesticide Guidelines (pdf)
• Toxicity of Common Lawn, Garden, and Ornamental Pesticides in Iowa (pdf)
• Understanding Pesticide Labels (pdf)
• Small Sprayer Calibration (pdf)
• Factors Affecting Pesticide Drift (pdf)
• Integrated Pest Management for Home Gardens and Landscapes (pdf)
• Protecting Bees from Pesticides (pdf)