KENNEWICK -- Because of environmental concerns, during the past 10 to 15 years, gardeners have lost the use of many familiar "tried and true" garden insecticides, such as diazinon.
This left gardeners wondering if their only recourse was surrendering when insects attacked the garden. For devoted gardeners, surrender was not an option and now other options are available to help.
One earth-friendly effective biological pesticide is spinosad. Spinosad, derived from the fermentation byproducts of a soil microorganism, must be ingested by insects of be effective. Once ingested, it attacks the insect's nervous system, causing rapid over-excitation and death in one to two days.
Because it has to be eaten to be effective, spinosad products work best against leaf feeding insects such as caterpillars, loopers, leafminers, thrips, sawflies, and leaf beetle larvae. It also is effective against fruit flies, spider mites and fleas (when used as an oral flea medication) on dogs. It does not appear to harm nonleaf feeding beneficial insects such as ladybugs, green lacewings and predatory mites.
Spinosad can be found in several home garden product lines including Bonide Captain-Jack's Deadbug Brew, Monterey Garden Spray and Bulls-Eye Bioinsecticide.
Neonicotinoid pesticides, a newer category of insecticides, also have become available to home gardeners. Neonicotinoid pesticides are the synthetic versions of the highly toxic natural insecticide, nicotine. Like nicotine, they work by causing excitation of an insect's nerves, then paralysis, and eventual death.
One of the neonicotinoids that many gardeners know well is imidacloprid, which is a systemic material that is applied to soil and taken up by the roots of trees and shrubs. Imidacloprid has a long period of residual activity and is considered very effective against sucking insects, whiteflies, turf insects, beetles, and a few tree borers. Insects die after sucking or eating the leaves of treated plants. Applied as a drench, it allows gardeners to control insects in large trees without needing special equipment to reach the tops or worrying about wind and the resulting spray drift.
Numerous home garden soil applied systemic insecticides contain imidacloprid. Bayer Advanced products initially were the only home garden products that contained imidacloprid because Bayer held the patent. Now that imidacloprid is off patent, it is appearing in other lines of home garden pesticides. Products include Bayer Advanced 12 Month Tree & Shrub Protect & Feed, Monterey Once-a-Year Insect Control, and Ortho Tree & Shrub Insect Control. Imidacloprid can also be found in products that are applied as sprays to plants.
Another neonicotinoid, clothianidin, is being introduced in the some of the Bayer products, such as Bayer Advanced 12 Month Tree & Shrub Protect & Feed Concentrate, that once only contained imidacloprid. Yet another nionicotinoid is acetamiprid. It is applied as a spray and can be found in various Ortho garden products, such as Ortho Flower, Fruit & Vegetable Insect Killer and Ortho Rose & Flower Insect Killer. It is a systemic applied as a foliar spray for control of aphids, various other sucking insects, beetles, armyworms and other caterpillars of both ornamentals and edible crops.
These new products generally have relatively low toxicity to humans and animals, but this isn't necessarily true with bees and other wildlife. The neonicotinoids are highly toxic to bees and are being blamed in parts of Europe for massive bee die-off. So while we gardeners may have new chemical tools available to assist us in fighting insect attacks, we should always read and follow label directions to protect the beneficial wildlife in our gardens.
* Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.