Texas Cooperative Extension,
Texas A&M University, College Station, Texas

March 2004

Spinosad: An Insecticide To Make Organic Gardeners Smile

by Dr. Michael Merchant, Urban Entomologist
Texas A&M University, College Station, TX

Still looking for an environmentally-friendly insecticide that won't harm beneficial insects, but still sticks it to pesky pests? You may need to look no further.

Spinosad (pronounced spin OH sid) is a relatively new insect killer that quickly and safely controls a variety of caterpillar, beetle and thrips pests. Spinosad is derived from the fermentation juices of a lowly soil bacterium called Saccharopolyspora spinosa. To chemists, spinosad is a complex molecule known as a "glycosylated macrolactone;" but to gardeners with a hankering for safer products, it may be a godsend.

Spinosad is not particularly new, having been granted organic status by the USDA National Organic Program (NOP) in 2003. However few home gardeners are aware of its potential uses.

Spinosad is especially effective on caterpillars and thrips. If you're a flower gardener, your ears should prick up on this one. Thrips and caterpillars are the two most important pest groups on annual and perennial flowers. Perhaps the best thing about spinosad-containing products is their safety for people and beneficial insects. Spinosad is safe for adult butterflies and many insect predators and parasites. It falls into the safest human health category as well.

Bacillus thuringiensis, known for years to savvy gardeners as "Bt", has been a standard weapon for the war against caterpillars. As an insecticide, Bt is a safe, selective product for caterpillars. However, Bt lacks staying power. Instead of Bt's one or two days' residual, spinosad keeps killing for up to four weeks. In addition, spinosad kills thrips, which Bt doesn't faze.

Last year a new wettable powder version of spinosad, EntrustR, was labeled for use on a wide variety of insect pests on organic crops, fruits, and vegetables. For commercial applicators working around home landscapes, spinosad is sold as a fire ant bait (Justice), and as a liquid spray for turf and ornamentals (ConserveR SC).

Because spinosad is a relatively new compound, it's not yet found its way onto many garden store shelves. Look for spinosad under the following trade names: Monterey Garden Insect SprayR, Ferti-lomeR Borer, Bagworm, Leafminer & Tent Caterpillar Spray, and Bulls-EyeTM Bioinsecticide. Ask in your local garden center, or search for these online. Because commercial names change daily, ask your nurseryman for additional products containing the active ingredient spinosad. Or look carefully on the 'ingredients' statements of new products for spinosad. Your garden will appreciate it, though the caterpillars may not.