This project aim to evaluate the efficiency of spreading droplets in solutions with biological insecticide and adjuvants in leaves of different varieties of cassava. The experimental design was entirely randomized in a factorial 3x7, with four replications. It was performed three solutions with biological insecticide, with and without adjuvants: Bacillus thuringiensis (500 g ha-1, Dipel WP® - 32.0 g Kg-1), B. thuringiensis (500 g ha-1) + glicerine (0.5% v v-1 , Hygrogem® byproduct from the soybean biodiesel) and B. thuringiensis + mineral oil (0.5% v v-1, Nimbus®) and were evaluated in seven varieties of cassava (Baianinha, Cascuda, Fécula Branca, IAC 118, OlhoJunto, Peru and IPR-União). The spreading of droplets of the solutions was evaluated on adaxial and abaxial leaf surfaces of the varieties. Only the treatment B. thuringiensis+mineral oil caused surface tension reduction of the drops in about 34.43% and 33.74% in relation to the others treatments B. thuringiensis and B. thuringiensis + glicerina, respectively. The treatment B. thuringiensis + mineral oil caused the greater spreading of the droplets on the adaxial surface of the leaf than the others treatments. The treatment B. thuringiensis + mineral oil caused greater spreading of the droplets in the abaxial surface of the leaf to the varieties Cascuda and Olho Junto. It was concluded that the spreading of the drops of solutions with biological inseticide in leaf surfaces of cassava varieties was dependent of adjuvant added to solution.