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Spinosad: a naturally derived insecticide (click here for publications in PDF format)


Spinosad (Dow Agrosciences) is a naturally-derived insecticide produced by fermentation of Saccharopolyspora spinosa, an actinomycete bacterium originally isolated from a Caribbean soil sample.

It is a neurotoxin comprising a mixture of spinosyns A and D (hence spinosAD), which are tetracyclic-macrolide compounds that act upon the post-synaptic nicotinic acetylcholine receptor and the GABA receptors.

In reality, S. spinosa produces a great many spinosyn compounds, but so far, only spinosyns A and D have been developed as the basis for commercial insecticide products.
 

Structure of spinosad: the R group is a hydrogen atom in spinosyn A and a methyl group in spinosyn D.

The difference between spinosyns A and D lies in the "R" group.  Small structural differences in other spinosyns have important effects on their biological activity.

          

The parasitoid Chelonus insularis comes into contact with spinosad residues during oviposition on surface contaminated egg masses of its host, Spodoptera frugiperda.

Testing parasitoid (Chelonus insularis) responses to spinosad contaminated egg masses from Spodoptera frugiperda


Spinosad is highly active by ingestion and to a lesser degree by contact. Spinosad-based products have been registered in more than 30 countries for control of pest Lepidoptera, Diptera, some Coleoptera, termites, ants and thrips.

Spinosad has very little mammalian toxicity and is classified by the United States Environmental Protection Agency as an environmentally and toxicologically reduced risk material.

A recent review of predator and parasitoid susceptibility to spinosad (Williams et al., 2003) concluded that this product represented one of the most judicious insecticides available for the conservation of predator populations.

However, the majority of studies have reported adverse effects on populations of hymenopteran parasitoids.

Sublethal effects on parasitoid longevity and reproduction are also more commonly observed in insect parasitoids compared to predator species.

 

          


The need for accurate assessment of the environmental impact of agrochemicals is clear.  Large areas are now being treated with spinosad, for example to control fruit flies.

Such studies are also relevant because spinosyns form the basis for a new generation of spinosyn analogues (spinosoids) currently being developed for improved environmental stability and an altered spectrum of insecticidal activity.

My work has focused on:
 

●  Evaluation of the toxicity of spinosad to non-target insects, particularly natural enemies (insect predators and parasitoids).
 

●  Use of ultra-low rates of spinosad in granular feeding stimulants for control of fall armyworm (Spodoptera frugiperda).
 

●  Potential of spinosad for control of mosquito vectors of medical importance (Aedes, Culex, Anopheles).
 

Spodoptera frugiperda larvae infesting maize (corn) can be controlled using tiny quantities of spinosad in an experimental phagostimulant formulation.

Experimental granular formulation of spinosad based on maize flour for control of Spodoptera frugiperda (see Williams et al. 2003).

 

          
 


Click here for publications on spinosad
 

 
          
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HOMEPAGEIridovirusesEcology of baculovirusesVirus insecticidesMosquitoes blackflies & ticksPredators, parasitoids, pathogensOthersStudents

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Trevor Williams - página personal en español