Over the last several years we've talked about some of the new, more environmentally friendly pesticides becoming available to home gardeners. These new products are helping replace pesticides that had been around for many years, such as diazinon, thiodan and chlorpyrifos.

Concerns about the health risk these older materials posed to humans, especially children, led to them being withdrawn from the home garden market.

Left without familiar pesticide products, the last few gardening seasons have been a challenge as gardeners tried to manage insect pests using newer, less familiar materials. Some of these products work quite well, but it's important for gardeners to know how to use them effectively.

With the growing season and the pest season at hand, now is the perfect time to review several of these new home garden pesticide products.

Spinosad: Here's one new product that I predict will become a mainstay pesticide for gardeners.

The spinosads are fermentation products of a soil bacterium. They have insecticidal and some even have miticidal properties. Insects are killed when they come in direct contact with the spinosad material or when they move onto treated surfaces.

Insects are also killed by eating treated plant tissues. Spinosads work by exciting the insect's nervous system, leading to muscle contractions, prostration with tremors, paralysis and death.

Spinosad insecticide is most effective against a variety of different caterpillars, leaf beetle larvae, leaf miners, and some other pests too.

Of particular interest to local gardeners is its control of thrips, Colorado potato beetle, corn earworm, codling moth and cherry fruit fly. Unlike many of the other newer chemicals available to gardeners, it provides some residual control.

Common home garden products on the market containing spinosads are Monterey Garden Insect Spray (Monterey Lawn & Garden), Bull's-Eye Bioinsecticide (Gardens Alive), Green Light Lawn & Garden Spray Spinosad (Green Light) and Ferti-Lome Borer, Bagworm, Leafminer, & Tent Caterpillar Spray.

Imidacloprid: Imidacloprid is the oldest member of a major new chemical family of insecticides called neonicotinoids. They work by interfering with the transmission of impulses in the insect nervous system. When exposed to imidacloprid, insects stop feeding soon after treatment and typically die within one to two days. It's relatively fast action and long residual activities are highly desirable characteristics. However, its systemic properties are what make it particularly useful and effective.

While some formulations of imidacloprid are applied as foliar sprays, gardeners find the formulations that are applied as a root drench very useful. All a gardener needs to do is mix it with water, then apply it to the soil for uptake by the roots. This avoids the difficulty of spraying tall plants or spraying under windy conditions.

Applied as a drench and taken up by the roots, it provides good control of many sucking insects, including aphids, adelgids, thrips, lacebugs, some scales, bugs, pyllids and mealy bugs. It's also effective against certain leaf beetles and leaf-miners.

One drawback in using imidacloprid is that when applied to the soil for uptake by the roots, it may take several weeks to several months to be fully absorbed and moved throughout the plant, especially in large trees.

However, once distributed throughout the tree, it's effective for six months or more. The other drawback for gardeners is that it's only labeled for use on ornamental plants and trees, not on vegetables or tree fruit.

Common home garden products containing imidacloprid are packaged by only one company, Bayer Advanced. Their Tree & Shrub Insect Control Concentrate (drench), Rose & Flower Insect Killer Concentrate (spray), and All-in-One Rose & Flower Care (drench with a systemic fungicide) all contain imidacloprid.

Esfenvalerate: Esfenvalerate is one of the many pyrethroids used for insect pest control.

Pyrethroids are synthetic pyrethrin. (Pyrethrin is a naturally occurring plant derived insecticide.) The newer pyrethroids like esfenvalerate have been designed to be longer lasting than the earlier pyrethroids. Like many other insecticides, pyrethroids kill by overexciting the insect's nervous system. Esfenvalerate provides a quick knock-down of many sucking and chewing insect pests and it has some residual control.

Several products containing esfenvalerate are labeled for use on garden vegetable crops as well as ornamentals and one is also labeled for use on fruit.

These esfenvalerate containing products are Bug Buster (Monterey Lawn & Garden Products), Ortho Bug-B-Gon Garden & Landscape Insect Killer Concentrate (Ortho), and Ortho Bug-B-Gon Max Garden & Landscape Insect Killer RTU (Ortho).

Cyfluthrin: Is another synthetic pyrethroid that works on contact and as a stomach poison. It's used to control a variety of sucking, flying and chewing insects.

It can be found in two Bayer Advanced products, Rose & Flower Insect Killer and Power Force Multi-Insect Killer.

When using the newer insecticide products (or older familiar ones), it's always best to read the label before mixing and applying. While these new products may be safer for us to use, they still can cause problems when used improperly. Some are highly toxic to bees, fish or other wildlife. Read the label thoroughly and follow all the precautions.

* Marianne C. Ophardt is a horticulturist for the Washington State University Cooperative Extension Office in Benton County.