AbstractBACKGROUNDImprovements in the virulence of the fungal pathogen Metarhizium acridum can crucially promote its efficacy to control locusts and grasshoppers. The polysaccharide components of the cell wall remarkably contribute to fungal virulence.RESULTSHere we found that M. acridum lacked the gene families of glycerate‐3‐kinase (GLYK) as the synthesis enzymes of saccharides. We then generated mutants by introducing the GLYK gene from the host‐generalist M. robertsii into the host‐specialist M. acridum. Consequently, compared with the wild‐type strain, the mutant strain (Ma::MrGLYK) increased the level of phospho‐6‐fructose in mycelia, the length and density of the mannan fibril layer on the cell wall. The mutant strains increased the mannan fibril in the cell wall and resistance to heat stress. Further transcriptome analysis showed that compared with the wild‐type strain, topical infection of Ma::MrGLYK strain induced higher expression of genes such as pattern‐recognition proteins, serine protease, and CYP450s in locusts, while reduced the expression of antimicrobial peptide and phenoloxidase activity. Moreover, topical infection and injection of Ma::MrGLYK significantly increased the mortality and shortened the lifespan of locusts compared with wild‐type M. acridum.CONCLUSIONOur study highlighted the application potential of the novel genetically modified fungal mutant of the host‐specialist M. acridum as a biocontrol agent against locust plagues. © 2020 Society of Chemical Industry