Resumo
Background: Alphitobius diaperinus, lesser mealworm, represents one of the most important pests in the poultry farming industry worldwide. This insect serves as a mechanical host of pathogenic micro-organisms to birds and causes injuries in their digestive tract affecting the feed conversion. Both larvae and adult insects grow in the avian bed, over the soil of sheds and especially near the feeders, where there is a greater availability of food and water. Alphitobius diaperinus control, around the world and especially in Brazil, is based exclusively on chemical agents which generates resistant populations. The biological control by entomopathogenic fungi has been shown to be feasible and satisfactory when tested in vitro testing in the recent years. However it still lacks tests to evaluate these agents in environments that simulate field conditions. So, the aim of this experiment was to evaluate a Beauveria bassiana (986) as a way of biological control of A. diaperinus in poultry bed of wood shavings. Material, Methods & Results: Alphitobius diaperinus were collected from a poultry shed located in Garibaldi in Rio Grande do Sul and sent to the Laboratório Central de Diagnósticos em Patologias Aviárias (LCDPA), Universidade Federal de Santa Maria (UFSM). Then they were cultivated in plastic boxes on the poultry bed and fed as the recommended protocol. The Beauveria bassiana (986), isolated from ticks, was purchased from the Department of Entomology of ESALQ/USP and cultivated on Potato Dextrose Agar medium (PDA) at 27ºC, 80% RH for 4 days before the experiment. The conidia suspension was obtained through scraping cultivation with aqueous solution of Triton X-100 (0.01%) in the concentration of 3,83 x 108 mL-¹. Six plastic boxes were used, containing 8 cm of soil and 10 cm of sterile wood shavings in order to allocate the beetles. In each box, 400 insects (100 larvae and 300 adults) were divided into two groups - G1: 3 boxes treated with 27 mL of suspension conidia (3,83 x 108 mL-¹) and G2: 3 boxes treated with aqueous solution of triton x-100 0.01% - assisted by 7 days in an average temperature of 32.5°C and 72.4% RH and, after this period, the mortality of both larvae and adults was evaluated. There was no mortality of insects in any stage of the development. Discussion: Non-occurrence of deaths in the larval stage in this test can be explained by the fact that the larvae have the habit to dig galleries on the ground and they usually remain there to maintain a more propitious temperature to their development, preventing contact with the suspension. It was not assessed a longer time of incubation, because seven days are considered to be the average that approximates the most close to the period of time used in the system "All in All out" in the Brazilian poultry farming, period which would be used to apply the fungal solution in poultry sheds. In this experiment, the temperature did not exceed 34ºC, and even so this factor may have affected the growth of fungus in the containers. Another possibility would be a lower virulence of isolated 986 front A. diaperinus, since this isolated was obtained from ticks. In this experiment, the Beauveria bassiana isolated 986 was not effective for biological control of Alphitobius diaperinus in simulated ambient of poultry bed. So, factors as soil, wood shavings, high temperature and incubation time would interfere in the effectiveness.