Étude in vitro de l’effet larvicide des champignons entomopathogènes indigènes (Fusarium sp.) sur la chenille processionnaire du pin d’Alep

Abstract

The pine processionary caterpillar is one of the main defoliators of Aleppo pine forests in the Mediterranean basin. Although chemical control is still used due to its immediate effectiveness, it raises concerns regarding pest resistance and the environmental impact of pesticides. These limitations have prompted the search for more sustainable alternatives based on the use of natural agents within the framework of biological control. In this context, the present study aimed, on the one hand, to search for native entomopathogens and, on the other, to evaluate in vitro the larvicidal activity of two Fusarium sp. strains (FUSR and FUSB) on this pest. The first part of this study involved the selection, among ten fungal strains tested, of those capable of infecting healthy larvae. Post-inoculation observation revealed that 60% of the strains caused visible sporulation on the surface of the caterpillars. Fungal isolation from colonized larval cadavers led to the identification of fungi belonging to the Fusarium and Beauveria genera. In parallel, isolation from eight naturally mummified caterpillars previously stored in the laboratory showed a predominance of Fusarium (50%), followed by Beauveria (37%) and Aspergillus (13%). The results of the second phase, concerning the larvicidal activity of entomopathogenic fungi, showed that Fusarium sp.2 (FUSB) exhibited significantly higher virulence than Fusarium sp.1 (FUSR). At a high dose (***spores/ml), FUSB induced ***% larval mortality, compared to ***% for FUSR. Furthermore, the comparison of lethal doses (DL50) confirmed this difference: FUSB showed a DL50 of ***spores/ml, significantly lower than FUSR (***spores/ml). Statistical analysis revealed a significant difference between the two fungal strains (p = 0.020 < 0.05), confirming that FUSB was significantly more effective than FUSR under experimental conditions. This study confirms the entomopathogenic potential of local fungal strains to control the Aleppo pine processionary and opens perspectives for their integration into biological control strategies in forestry.