Journal of the American Mosquito Control Association: Vol. 22, No. 1, pp. 93–96.
LABORATORY EVALUATION OF THE BIOINSECTICIDE SPINOSAD FOR MOSQUITO CONTROL
R. ROMI,a S. PROIETTI,a M. DI LUCA,a and M. CRISTOFAROb
aDepartment of Infectious, Parasitological and Immunomediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161 Roma, Italy
bEnea C. R. Casacccia, Biotech Sic, Roma, Italy
Spinosad, a naturally occurring product of the fermentation of the bacterium Saccharopolyspora spinosa, is a highly effective bioinsecticide against a broad range of agriculturally important insect pests, and this agent has an excellent environmental and mammalian toxicological profile. In this study the efficacy of a Spinosad-based product (Laser® 4.8% emulsifiable concentrate) was evaluated in laboratory bioassays against laboratory-reared mosquito strains of 3 species of medical importance: Aedes aegypti, Anopheles stephensi, and Culex pipiens. Spinosad was particularly effective against larval Aedes and Culex, with a less marked activity against anophelines (24-h median lethal concentration = 0.0096, 0.0064, and 0.039 mg/liter, respectively), showing a persistence of the insecticide action of about 6 wk in laboratory containers. The activity of the Spinosad-based product against adult mosquitoes (toxicity by ingestion and a possible irritant or repellent effect on gravid females) also was evaluated. Results are discussed and compared with those available in the literature.
The naturally derived insecticide spinosad is highly toxic to Aedes and Anopheles mosquito larvae.
ECOSUR, Tapachula, Chiapas, Mexico.
Spinosad is a naturally derived biorational insecticide with an environmentally favorable toxicity profile, so we investigated its potency against mosquito larvae (Diptera: Culicidae). By laboratory bioassays of a suspension concentrate formulation of spinosad (Tracer), the 24 h lethal concentration (LC50) against Aedes aegypti (L.) third and fourth instars was estimated at 0.025 p.p.m. following logit regression. The concentration-mortality response of third- and fourth-instar Anopheles albimanus Weidemann did not conform to a logit model. The LC50 value of spinosad in Anopheles albimanus was 0.024 p.p.m. by quadratic linear regression. A field trial in southern Mexico demonstrated that spinosad 1 p.p.m. compared with the standard temephos (Abate) 1% granules 100 g/m3 water prevented Ae. aegypti breeding in plastic containers of water for 8 weeks; at 10 p.p.m. spinosad prevented breeding for > 22 weeks. In another field trial, spinosad at 5 p.p.m. and temephos both completely eliminated reproduction of Ae. aegypti for 13 weeks. In contrast, the bacterial insecticide Bacillus thuringiensis var. israelensis (Bti, Vectobac) AS) performed poorly with just 2 weeks of complete inhibition of Ae. aegypti breeding. Spinosad also effectively prevented breeding of Culex mosquitoes and chironomids in both trials to a degree similar to that of temephos. We conclude that spinosad merits evaluation as a replacement for organophosphate or Bti treatment of domestic water tanks in Mesoamerica. We also predict that spinosad is likely to be an effective larvicide for treatment of mosquito breeding sites.