Fungos entomopatogênicos no controle do Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) como estratégia de biosseguridade na avicultura

Abstract

The objective of this study was to assess the action in vitro of isolates of Beauveria bassiana, Cladosporium sp. and Trichoderma sp.. and control their entomopathogenic Alphitobius diaperinus known as "lesser mealworm." The objective was also to evaluate the safety of the entomopathogenic fungus Beauveria bassiana in broiler performance measured by productivity, hematological and histological analysis. In the first test of lesser mealworm larvae and adults were inoculated with conidia suspensions of the three species of fungi, at concentration of 107 conidios.mL-1 and observed for a period of ten days. The results were submitted to the qui-squared (χ2), which could be observed a higher mortality of beetles for strain of B. bassiana compared with the strains of Cladosporium sp. and Trichoderma sp. These results also showedthat the larvae were more susceptible than the adults. Faced with these results, an assessment was made of entomopathogenic B. bassiana by inoculation of 200 insect larvae and 200 adults with suspensions of conidia at concentrations of 106, 107 and 108 conídios.mL-1. The insects were observed for ten days, and the results submitted to analysis of variance and the averages compared by the Kruskal-Wallis test at 5% significance. The mortality in the larvae was significant after the fourth day with the lowest concentration, and mortality was significant only in adults after the fifth day in the concentration of 108 conidios.mL-1. In the safety test were used 240 broiler chickens from the commercial line Cobb, housed in metal batteries with twenty-four compartments of 0.90 x 0.85 x 0.40 meters. The distribution of birds was completely random and treatments were distributed in an experimental design in randomized blocks, with four treatments and six replications: T1 - control (saline + tween), T2 - suspension with 106 conidios.mL-1, T3 - suspension with 107 conidios.mL-1, and T4 - suspension with 108 conidios.mL-1. The inoculation was performed on the 14th and 28th days of age and each treatment used 0.5 mL for oral inoculation and a drop for nasal inoculation. The results were analyzed based on the analysis of variance, and the averages compared by Newman-Keuls test, with 5% significance. There were no statistical differences in weight gain and feed intake between treatments, although in the 108 conidios.mL-1 concentration occurred a lower weight gain compared to 106 concentration conidios.mL-1. At this concentration, the feed conversion was equal to control, with lower results than the other treatments. There was no statistical difference for viability. Regarding weight gain, the absolute and relative heart and liver weights were not significantly affected by concentrations of fungi. The blood evaluation showed significant increase in the total number of leukocytes (leukocyteses) in the group that received the highest concentration of fungus. Compared to white blood cell, there was statistical difference, with increase in the total number of leukocytes, lymphocytes, monocytes and heterophils at the concentration 108 conidios.mL -1. The histopathological analysis revealed no apparent lesions in lungs and Fabricius’ bursa , at any concentrations of fungi tested. However, the histopathological analysis revealed liver necrosis with focal coagulation and infiltrated leukocyte presenting heterophils and mononuclear cells, mainly around the bile duct, which showed no apparent injuries and cellular arrangement within the normal range. These lesions were moderate at the concentration 107 and more pronounced at 108. Studies show the efficiency of Beauveria bassiana isolatedin the control of Alphitobius diaperinus, indicating that the B bassiana is a promising fungus on pest control, although more efficient in larvaecontrolling . Although no substantial change has occurred, the small hematological and histopathological changes may have caused the severe challenge they have suffered, indicating a possible dose-effect relationship of organic product. However, further studies are still needed to define more precisely the application of this control agent in the management of lesser mealworm, always considering the cost-benefit ratio.