Resumo. The lesser mealworm Alphitobius diaperinus (Panzer) is considered one of the most important pests of modern aviculture. Alternatives to control this insect include entomopathogenic fungi Beauveria bassiana (Bals.) Vuill. as well as diatomaceous earth (DE). This study aimed to evaluate the interaction of these agents for lesser mealworm control, in two humidity conditions. The experiment consisted of six treatments, at 55% and 95% of humidity, as follows: DE applied 2g.kg-1; B. bassiana at 5×107; and 5×108 conidia.g-1; DE (2g.kg-1) + B. bassiana at 5×107; and 5×108 conidia.g-1, and control. The agents were mixed with the bird food and distributed into Petri dishes with 15 adults were released in each replicate (three replicates per treatment). The viability of the fungus associated to DE also was checked. It was verified that DE significatively affect the fungi viability at 95% of humidity. The highest mortality values were verified at 55% humidity, and treatments where the agents were combined performed better (97.8%).The combined agents also showed the greatest activity at 95% humidity; however, mortality was lower than 70%. With regard to their interaction, a positive effect occurred at the higher humidity only, in which a synergism was verified for both concentrations of the fungus. We concluded that the use of both agents could be a good strategy as long as they are used at smaller amounts, which is quite interesting economically in a program for the integrated management of the pest.