Control Garden Pests Organically With Spinosad

Leaf miners, thrips, fire ants and fleas — bugs Bt can’t handle — are no match for this organically approved bacterium.

| June/July 2011

  • Organic Pest Contol
    Spinosad is an organic gardener’s weapon against caterpillars, leaf miners, fire ants and more.

  • Organic Pest Contol

Many of the pests that plague gardeners are caterpillars and other leaf-eating insects. Only caterpillars can be controlled with the well-known biological pesticide Bt (Bacillus thuringiensis), but a newer biological pesticide, spinosad, can control caterpillars as well as leaf miners, thrips, Colorado potato beetle larvae, and even fire ants and fleas.

The spinosad parent bacterium, Saccharopolyspora spinosa, was discovered in 1982 in an old Caribbean rum still. It was soon found that these bacteria produce a substance that works as a neurotoxin in many (but not all) insects. Susceptible insect species that are exposed to spinosad become excited to the point of exhaustion, stop eating immediately and die within two days.

Similar to Bt, spinosad breaks down in sunlight, so late-day applications will better expose insects to the toxins. Spinosad has a longer period of residual effectiveness compared with Bt, often providing good protection from pests for five to seven days. Generally, spinosad is most effective against insect larvae, so it’s important to look carefully for eggs and feeding insects before you spray.

The Organic Materials Review Institute currently lists 21 approved spinosad products, including the following for use in the garden: Entrust Naturalyte Insect Control, Green Light Lawn and Garden Spray with Spinosad, Monterey Garden Insect Spray, and others. Several more have been approved for control of fire ants.

Uses for spinosad go beyond the garden — it’s even being used to prevent fleas in dogs. Given monthly in the form of a pill, a product called Comfortis makes dogs uninhabitable to fleas for 30 days. Spinosad is also the active ingredient in a product called Natroba, recently approved by the FDA to control head lice, which affect 6 to 12 million American children every year. Spinosad provides a reliable alternative to lice-control products containing permethrin (a synthetic pesticide used as the active ingredient in several treatments), and is especially helpful in cases involving permethrin-resistant lice.

A note of caution: Although spinosad is not as broad-spectrum nor as long-lasting as many synthetic insecticides, it can kill bees and other beneficial insects along with pests. So use it sparingly — only when you think you have to.

6/20/2019 10:49:21 AM

I am finding Spinosad is effective on adult potato beetles as well as larvae. I sprayed on a calm,damp morning 4 days ago on adults laying eggs on the new crop , sometimes many beetles on one small plant.. Today no sign of bugs but for one or two. I am watching some of the egg clusters to see if it damaged them.

6/10/2019 9:54:18 AM

MJo Stanley: It is my understanding that Spinosad is only toxic to honey bees in liquid form. I believe that if you apply it in the evening after the bees have retired it will be dry by morning & safe for your bees.

MJo Stanley
5/29/2018 11:47:55 AM

Spinosad was recommended for viburnum leaf beetle which has been ferocious here in the pioneer valley of Massachusetts this year. I am concerned that it kills bees and wonder if there is an alternative that is safe for bees. I don't want to harm any bees. thanks



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