###### Abstract  
The beetle _Anthonomus grandis_ [PERSON], 1843, is the main cotton pest, causing enormous losses in cotton. The breeding of genetically modified plants with _A. grandis_ resistance is seen as an important control strategy. However, the identification of molecules with high toxicity to this insect remains a challenge. The susceptibility of _A. grandis_ larvae to proteins (Cry1 Ba, Cry7 Ab, and Mpp23 Aa/Xpp37 Aa) from _Bacillus thuringiensis_ [PERSON], 1915, with toxicity reported against Coleopteran, has been evaluated. The ingestion of different protein concentrations (which were incorporated into an artificial diet) by the larvae was tested in the laboratory, and mortality was evaluated after one week. All Cry proteins tested exhibited higher toxicity than that the untreated artificial diet. These Cry proteins showed similar results to the control Cry1 Ac, with low toxicity to _A. grandis_, since it killed less than 50% of larvae, even at the highest concentration applied (100 \(\mu\)g-g\({}^{-1}\)). Mpp/Xpp proteins provided the highest toxicity with a 0.18 \(\mu\)g-g\({}^{-1}\) value for the 50% lethal concentration. Importantly, this parameter is the lowest ever reported for this insect species tested with _B. thuringiensis_ proteins. This result highlights the potential of Mpp23 Aa/Xpp37 Aa for the development of a biotechnological tool aiming at the field control of _A. grandis_. cotton boll weevil; Cry proteins; Mpp/Xpp proteins; Cry23 Aa; Cry37 Aa; Coleoptera; Curculionidae  
Lavae. The cotton boll weeevil is a Coleopteran insect, considered the most harmful cotton pest, and its stereotypic behavior makes control difficult [4]. In addition to feeding on the flower buds, after mating, females lay eggs inside the fruiting structures of the cotton plant, where the development of all immature stages of the insect occurs, causing abscission or reduction in fiber quality [5]. In addition, newly emerged or old adults are commonly protected by the flower bud bracts or refugees in plants outside of the cotton crops, decreasing exposure to mortality factors, i.e., insecticides applied by spraying [6]. Once the insect is detected in pheromone traps, insecticide applications are performed, using mainly malathion. These applications can be performed weekly until the insect is no longer detected. Consequently, the field may receive as many as 25 applications in a single growing season, boosting expenses regarding agricultural inputs, and negatively affecting the environment and entomofauna [7; 8; 9]. However, the low effectiveness of the available synthetic agents has contributed to inefficient control measures, an increase in the insect population, and its genetic diversity. In addition, the non-existence of conventional or transgenic commercial cultivars with some resistance to CBW has stimulated the search for new biotechnological tools for the effective control of this insect pest. The development of genetically modified crops expressing Cry and Vip toxins from _Bacillus thuringiensis_ (Bt) has been widely studied due to the toxic effect of these proteins, mainly against Lepidoptera [10]. Interestingly, transgenic plants expressing insectical proteins from Bt are effective in controlling stem borers, ear feeders, and rootworms [10]. Therefore, cotton plants expressing Bt proteins (toxic to CBW) may also control this devastating insect pest. Currently, transgenic cotton plants expressing _cry_ and _vip_ genes to control Lepidoptera are already being commercially launched in Brazil, but to date, no variety or cultivar capable of controlling the beetle _A. grandis_ has been released [11; 12; 13]. The insect order Coleoptera comprises numerous species considered pests for the world's major crops, few of which have proved susceptible to Bt toxins [14]. Despite causing significant economic losses around the world, the number of studies carried out to identify Bt proteins active against beetles is lower than those performed in Lepidopteran insect species.