[Immediate larvicidal activity and residual action of the endotoxin of the serotype H-14 of Bacillus thuringiensis in 2 mosquito biotopes on the French Mediterranean coast].

The primary powder R.153.78 of the serotype H.14 of B. thuringiensis has been evaluated in small field plots against larvae of Ae. detritus and Cx. pipiens.. The minimal concentration of the primary powder inducing a complete mortality was 0.1 mg/1 against Ae. detritus and 0,4 mg/1 against Cx. pipiens, corresponding at dosages of respectively about 310-420 and 1240-1680 International Toxic Units per litre. The residual larvicide effectiveness was close to nil in spite of the chemical stability of the delta endotoxin in neutral and acid waters. Experimental formulations derived from this primary powder were less effective than, or at the best as effective as, the primary powder itself. The above findings confirm that the serotype H.14 of B. thuringiensis could constitute the basis of very effective new larvicides and suggest that formulation research has a major role to play to maximize the potential of this promising biological control agent.