No abstract

Entomopathogenic fungi (EPF) are insecticide alternatives for pest control. Their ability to easily adhere and quickly penetrate the insect cuticle is a key factor for their selection, which has received too little consideration so far. Here, we evaluated the impact of five EPF on the survival and fecundity of Drosophila suzukii, a worldwide invasive pest of soft-skinned fruits. We assessed the exposure time needed to achieve fly mortality as well as the mortality of two non-target insects: Orius laevigatus and Bombus terrestris, commonly encountered in greenhouses where D. suzukii is the most damaging. Drosophila suzukii were exposed for 3 hours to a fungal culture from each EPF and survival rates were assessed daily. Beauvaria bassiana was the most efficient EPF, killing over 95% of the flies within 10 days. Additional flies were then exposed to this fungus culture for 10 seconds, 1 minute, 10 minutes and 1 hour. The exposure time impacted the mortality rates: 50% of the flies died within 4 days after a 3-hours exposure to B. bassiana, whereas 6 days were needed to reach the same result with 10 seconds of exposure. Whatever the exposure time, this EPF always needed ten days to be lethal for more than 95% of individuals. Beauvaria bassiana was not lethal for the non-target species. Thus, B. bassiana is an option to control D. suzukii without harming beneficial insects. Further studies are now needed under real cultivation conditions to assess whether B. bassiana can be included in biocontrol strategies against D. suzukii.

The Green Revolution has greatly changed agricultural production methods. Agriculture has become more specialized and intensive, and the use of phytopharmaceutical products, including insecticides, has intensified. However, these are harmful to the environment and human health. At the same time, globalization has led to the introduction of alien species (called invasive), whose establishment in Europe has been facilitated by the abundance of nutritive resources and the absence of natural enemies. These observations are particularly true with Drosophila suzukii. This fly is now considered as the main fruit pest in the world. Thus, it is becoming urgent to find alternative control methods to insecticides to counter the economic damage caused by this new pest. However, the development of an integrated pest management approach requires an excellent understanding of the biology and ecology of the species. In this paper, we first present the state of knowledge on the life cycle, host plants and phenology of D. suzukii. The current geographical distribution and the history of invasion of this pest are detailed, before estimating the extent of the economic losses caused. In a second part, the known alternative control methods against D. suzukii are listed: cultural practices, post-harvest treatments, sterile insect releases, uses of natural enemies and behavioral manipulations (visual and olfactory). Finally, in a third part, we will see how these methods can be combined to improve the control of this pest.