Effects of Vectobac 12AS against chironomid midges

Vectobac12AS, supplied by Abbott Laboratories in USA, is an aqueous suspension formulation of Bacillus thuringiensis israelensis. It is widely used as mosquito and black fly larvicide not only in USA but also in the other countries. Now, we evaluated the effects of Vectobac12AS against chironomid midges.<br> High larvicidal activities were exhibited in the laboratory evaluation of Vectobac12AS against the final instar larvae of Chironomus yoshimatsui and Chironomus kiiensis, and the LC₅₀ values were estimated to be 0.045ppm and 0.102ppm active ingredient, respectively.<br> Two field trials of Vectobac12AS for the control of chironomid midges were carried out in different habitats. First trial was conducted at a river in Matsuyama, Ehime- pref. in 1996. A continuous application of Vectobac12AS for 60min, at the rate of 0.57ppm active ingredient against water flow volume, suppressed the larval density of the chironomid midges within two days at any point up to 400m downstream with 95.0% or more comparative redution rate. Moreover, adult densities of Glyptotendipes pallens and C. yoshimatsui at 600m downstream were also declined. These effects lasted for more than 1.5 months.<br> The second trial was carried out at a sewage treatment plant in Osaka-pref. in 1997. Vectobac12AS was applied to the final sedimentation tanks for 60min contineously. The application with 0.33ppm of the active ingredient resulted in excellent larval control of C. kiiensis living in the overflow gutters, inducing the reduction of adult density for 1 month. And also, Vectobac12AS exhibited control effects on bath room flies (Telmatoscopus albipunctus and Psychoda alternata) living at the same area. The effects on bath room flies were also continued for more than 1 month with high reduction rate.<br> These results suggest that Vectobac12AS is useful for the control not only of chironomid midges, but also of bath room flies.