Presidential Green Chemistry Challenge: 1999 Designing Greener Chemicals Award
CortevaTM Agriscience (formerly Dow Agrosciences LLC)
Spinosad: A New Natural Product for Insect Control
Innovation and Benefits: CortevaTM developed spinosad, a highly selective, environmentally friendly insecticide made by a soil microorganism. It controls many chewing insect pests in cotton, trees, fruits, vegetables, turf, and ornamentals. Unlike traditional pesticides, it does not persist in the environment; it also has low toxicity to mammals and birds.
Summary of Technology: Controlling insect pests is essential to maintaining high agricultural productivity and minimizing monetary losses. Synthetic organic pesticides, from a relatively small number of chemical classes, play a leading role in pest control. The development of new and improved pesticides is necessitated by increased pest resistance to existing products, along with stricter environmental and toxicological regulations. To meet this need, CortevaTM Agrisciences has designed spinosad, a highly selective, environmentally friendly insecticide.
High-volume testing of fermentation isolates in agricultural screens produced numerous leads, including the extracts of a Caribbean soil sample found to be active on mosquito larvae. The microorganism, Saccharopolyspora spinosa, was isolated from the soil sample, and the insecticidal activity of the spinosyns was identified. Spinosyns are unique macrocyclic lactones, containing a tetracyclic core to which two sugars are attached. Most of the insecticidal activity is due to a mixture of spinosyns A and D, commonly referred to as spinosad. Products such as Tracer® Naturalyte® Insect Control and Precise® contain spinosad as the active ingredient.
Insects exposed to spinosad exhibit classical symptoms of neurotoxicity: lack of coordination, prostration, tremors, and other involuntary muscle contractions leading to paralysis and death. Although the mode of action of spinosad is not fully understood, it appears to affect nicotinic and γ-aminobutyric acid receptor function through a novel mechanism.
Spinosad presents a favorable environmental profile. It does not leach, bioaccumulate, volatilize, or persist in the environment. Spinosad will degrade photochemically when exposed to light after application. Because spinosad strongly adsorbs to most soils, it does not leach through soil to groundwater. Spinosad demonstrates low mammalian and avian toxicity. No long-term health problems were noted in mammals, and a low potential for acute toxicity exists due to low oral, dermal, and inhalation toxicity. This is advantageous, because low mammalian toxicity imparts reduced risk to those who handle, mix, and apply the product. Although spinosad is moderately toxic to fish, this toxicity represents a reduced risk to fish when compared with many synthetic insecticides currently in use.
Spinosad has proven effective in controlling many chewing insect pests in cotton, trees, fruits, vegetables, turf, and ornamentals. High selectivity is also observed: 70–90 percent of beneficial insects and predatory wasps are left unharmed. Spinosad features a novel molecular structure and mode of action that provide the excellent crop protection associated with synthetic products coupled with the low human and environmental risk found in biological products. The selectivity and low toxicity of spinosad make it a promising tool for integrated pest management.
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