Spinosad

Spinosad (spinosyn A and spinosyn D) are a new chemical class of insecticides that are registered by the EPA to control a variety of insects. The active ingredient is derived from a naturally occurring soil dwelling bacterium called Saccharopolyspora spinosa, a rare actinomycete reportedly collected from soil in an abandoned rum distillery on a Caribbean Island in 1982 by a vacationing scientist. It has not been found in nature since that time, and was subsequently described as a new species. The bacteria produces compounds (metabolites) while in a fermentation broth. The first fermentation-derived compound was formulated in 1988. Spinosad has since been formulated into insecticides that combine the efficacy of a synthetic insecticide with the benefits of a biological pest control organism.

Mode of Action

Spinosad kills susceptible species by causing rapid excitation of the insect nervous system. Due to this unique mode of action, Spinosad is valued in resistance management programs. Spinosad must be ingested by the insect, therefore it has little effect on sucking insects and non-target predatory insects. Spinosad is relatively fast acting. The insect dies within 1 to 2 days after ingesting the active ingredient and there appears to be no recovery.

Use

It is used to control a variety of insect pests, including fruit flies, caterpillars, leafminers, thrips, sawflies, spider mites, and leaf beetle larvae. Spinosad is recommended for use in an Integrated Pest Management program for commericial greenhouses since it will not harm most beneficial insects or predatory mites. Spinosad does not significantly effect beneficial organisms including ladybugs, green lacewings, minute pirate bugs, and predatory mites.

Products

Spinosad has been formulated into two commercial products registered for use in commericial agriculture, including DowAgros' Conserve® SC, and Entrust®. Entrust® is approved for use on USDA certified organic produce.

There are several home garden product manufactured for use in the United States including Monterey Garden Insect Spray® manufactured by Lawn and Garden Products, Inc. and 'Borer, Bagworm, Tent Caterpillar & Leafminer Spray' manufactured by Ferti-Lome®.

The products have practically no odor. Its soil absorption is moderately strong and it degrades rapidly in the environment primarily through photolysis.

Safety

Its "Caution" signal word indicates a reduced risk to applicators and workers. There are no specific worker protection requirements, even though applicators and handlers should wear a long-sleeved shirt, long pants, shoes and socks.

Spinosad shows low toxicity when ingested by mammals (male rat LD50 = 3738 mg/kg) and no additional adverse effects from chronic exposure. Studies on spinosad show slight toxicity to birds, moderate toxicity to fish, and slight to moderate toxicity to aquatic invertebrates. However, it is highly toxic to bees (honey bee LC50 = 11.5 ppm) and is highly toxic to oysters and other marine mollusks. Applications to areas where bees are actively foraging should be avoided. After the residues have dried, it is much less toxic to bees.

Beneficial Trichogramma and Braconid wasps are harmed by the chemical, but it has much less effect on such insects as lacewings and beetles like the ladybug and spares predatory bugs such as damsel bugs and the big-eyed bug.

Spinosad does not have any phytotoxicity on ornamentals and is non-phytotoxic for most crops. It has a 4-hour Worker Protection Standard reentry interval (REI).

Do not apply Spinosad more than 10 times in a 12 month period inside a greenhouse to prevent possible insect pesticide resistance.

Sources

• Dow AgroSciences LLC. Conserve SC InfoSheet. Indianapolis IN.
• "A review of Spinosad" Tam Tran. University of California, Irvine.
• Extension Toxicology Network. Pesticide Information Profiles. EPA Pesticide Programs. [1]
• National Coalition Against the Mis-Use of Pesticides. [2]
• Bio-Itegral Resource Center. [3]