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Garden Insect Spray With Spinosad

By Jay Golberg ; Updated September 21, 2017
Spinosad is used to kill plant-eating worms and other pests in the garden.

Spinosad is a safe and effective pesticide when used as directed. It is used to control plant-eating caterpillars, beetles, dry wood termites and other pests while not harming beneficial insects. Spinosad is approved under the Organic Foods Production Act as an organic solution for pest control on over 150 crops. It is the active ingredient in many garden insect sprays.


Spinosad is made by fermenting the naturally occurring soil bacteria known as Saccharopolyspora spinosa. The bacteria is found in soils world wide but was first identified in a soil sample taken on a Caribbean island in 1983. When the bacteria is concentrated and fermented, the resulting broth is is highly toxic to many insect pests. It was first used to control caterpillars that had become resistant to other organic pest control methods.


The discovery of spinosad was a breakthrough for organic growers and provided several important benefits. For example, it has a longer residual period than most other organic pesticides. This means it stays viable in the field for several weeks rather than days. Also, it works by contact as well as ingestion. Most importantly, it is safe to use around butterflies and beneficial insects.


Spinosad works by contact or ingestion. When the target pest crawls across a treated surface or ingests a treated plant the spinosad causes extreme excitation of the nervous system. This leads to tremors, paralysis and eventual death of the insect. Ingestion of spinosad from eating treated vegetation is as much as 10 times more effective than contact. Spinosad kills or controls all caterpillars, spider mites, thrips, Colorado beetles and asparagus beetles.


The discovery and development of spinosad as a pesticide is significant because it takes the place of dangerous and environmentally damaging insecticides. Also, less spinosad is used per acre than standard pesticides. For example, only 3 oz. of spinosad is effective for pest control per acre to control pests compared to 5 lb. per acre for traditional pesticides. Because spinosad does not kill beneficial insects, the beneficial insects continue to kill bugs not killed by the spinosad application, further reducing the need for chemical pesticides.


Spinosad is highly toxic to bees if they have contact with the spray or dust. Do not apply the dust to blooming plants that attract bees. Spray the spinosad liquid on blooming plants in the evening when bees are less active and the liquid can be allowed to dry. Once the liquid is dry, the toxicity level for bees is greatly reduced.


About the Author


Jay Golberg is a certified Texas nursery professional and professional project manager. He has 30 years of business and farming experience and holds bachelor's degrees in English writing from St. Edward's University and finance from Lamar University.