Several formulations based on a palatable carrier suspension: Bacillus thuringiensis Berliner HD-133 strain; beet armyworm, Spodoptera exigua (Hübner), multiple nucleopolyhedrovirus (SeMNPV); and fall armyworm, Spodoptera frugiperda (Hübner), multiple nucleopolyhedrovirus (SfMNPV); alone or combined were developed and evaluated for activity against Spodoptera exigua and S. frugiperda larvae. Bioassays to determine the most active agents for each insect species were three treatments for spore-crystal complex, three for occlusion bodies for each of the two viruses, and four treatments combining all of them in different concentrations. Feeding preference was bioassayed with natural ingredients to obtain a palatable carrier for the active agents. Carrier suspensions were prepared with dehydrated soy leaves as a feeding stimulant for both pests for formulation preparation. Formulations containing the lower and medium concentrations of HD-133 strain and SeMNVP (SeB1V1 and SeB2V2) showed synergism against S. exigua, whereas formulations containing medium and high concentrations (SfB2V2 and SfB3V3, respectively) offered additive interaction against S. frugiperda.