Bollworms comprise the most harmful and economically relevant species of lepidopteran. Helicoverpa gelotopoeon (D.) (Lepidoptera: Noctuidae) is native to America and affects many crops. Tobacco is an industrial crop in which methods of pest control rely mainly on the application of insecticides. To develop new eco-friendly strategies against insect pests it is very important to overcome the side effects of insecticides. The utilization of fungal entomopathogens as endophytes is a new perspective that may accomplish good results. The present study aimed to evaluate the ability of endophytic Beauveria bassiana (Bals.-Criv.) Vuill. to affect H. gelotopoeon life parameters and feeding behavior on tobacco plants. Beauveria bassiana LPSC 1215 as an endophyte did not reduce the amount of vegetal material consumed by H. gelotopoeon larvae but affected the life cycle period of the plague, particularly the larval and adult stages. Also, egg fertility was affected since adults laid eggs that were not able to hatch. The results of this investigation provide new information on endophytic entomopathogen potential to be incorporated in Integrated Pest Management (IPM) programs.
Fungal entomopathogens can naturally regulate populations of various insects. The entomopathogen Beauveria bassiana (Bals.- Criv.) Vuill. is also able to endophytically colonize different plants. Endophytic colonization by entomopathogens may provide a source of indirect interactions between fungi and insects and has been associated with the ability of the fungus to control insect pests. The tomato leaf miner, Tuta absoluta (Meyrick) is considered one of the most devastating pests of tomato (Solanum lycopersicum L.) and its difficult control is due to its miner habit, short life cycle, and high reproductive capacity. The aims of this study were: (i) to use three different techniques, i.e. leaf spraying, seed immersion and root dipping, for the endophytic inoculation of B. bassiana in tomato plants; and (ii) to assess the effect of B. bassiana on tomato leaf consumption and mortality of T. absoluta after inoculation. The percentage of colonization by B. bassiana was assessed 7, 14 and 28 days after inoculation. All inoculation techniques employed allowed the recovery of B. bassiana, although our results showed significant differences between techniques. Leaf spraying was the most effective, with the highest percentage of colonization recorded 7 days after inoculation. We also evaluated (i) the effect on the mortality of T. absoluta by direct contact with conidia of B. bassiana, and (ii) the effect on tomato leaf consumption and mortality by indirect contact through ingestion of inoculated plant tissues with B. bassiana. Mortality bioassays showed that B. bassiana infected T. absoluta, either by direct contact or indirectly, via ingestion of inoculated tomato leaves. Direct contact showed a higher percentage of mortality and a lower median survival time (MST) than indirect contact. Significant differences in the mortality percentages of T. absoluta after exposure with B. bassiana were found among the treatments and the control. Our results suggest that the endophytic inoculation of B. bassiana in tomato crops provides the basis for further investigation, which should focus on the virulence of the endophytic B. bassiana against T. absoluta.
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