FACTORS AFFECTING THE EFFICACY OF 3 COMMERCIAL FORMULATIONS OF BACILLUS-THURINGIENSIS VAR ISRAELENSIS AGAINST SPECIES OF EUROPEAN BLACK FLIES

The efficacy of three commercial formulations of Bacillus thuringiensi s var. israelensis against two European blackfly species was determine d. The effect of seston concentration, temperature and larval size on the efficacy of the formulations was also determined. Teknar-WDC was f ound to be almost four times as effective as Bactimos-WP though only s lightly more efficient than Vectobac-AS against Simulium variegatum gp . larvae. Small larvae ( < 2.5 mm) were more susceptible to both Tekna r-WDC and Vectobac-AS than large larvae ( > 5 mm) though no difference was seen with Bactimos-WP. High seston concentrations both before and during bioassays significantly decreased the efficacy of all formulat ions. Increased temperatures increased the efficacy of all formulation s.