Harnessing Endophytic Fungi for Sustainable Pest Management: A Review

Endophytic fungi are increasingly investigated as biological components of pest management because some can inhabit living plant tissues while changing herbivore performance, host resistance or associated microbial communities. Their proposed advantages are attractive for integrated pest management, particularly against concealed feeders and pests difficult to reach with conventional foliar treatments. Yet the label ‘endophyte’ describes a location rather than an insect-control mechanism, and experimental success does not establish durable field protection. This critical narrative review integrates literature on grass-associated defensive symbionts, insect-pathogenic fungi with endophytic capacity, and selected root-associated nematophagous fungi. Evidence was evaluated across colonisation validity, experimental controls, mechanism, pest outcomes, ecological interactions and translational relevance. Studies support biologically plausible and sometimes experimentally demonstrated reductions in herbivore survival, reproduction or feeding, with especially informative evidence from tomato–whitefly systems and controlled studies of leafminers and internal feeders. Molecular work increasingly implicates plant specialised metabolites and defence signalling, whereas inoculation studies reveal pronounced effects of fungal strain, plant genotype, substrate, tissue and sampling time. Distinguishing fungal infection of insects from plant-mediated protection remains essential. Meta-analytic findings indicate an overall protective tendency but conceal substantial ecological heterogeneity; controlled pot experiments and short-term seedling assays still dominate important parts of the literature. Persistence, compatibility with natural enemies and crop protection programmes, livestock and non-target safety, and yield-adjusted economic benefit remain insufficiently documented across seasons and locations. The review proposes an evidence hierarchy linking verified internal colonisation and causal mechanism to pest suppression, crop performance and risk-adjusted sustainability. Endophytic fungi are best regarded as context-dependent candidates for integrated management rather than inherently persistent or universally benign bioinsecticides. Their practical value will depend on reproducible establishment, adequately controlled field trials and transparent assessments of both benefits and trade-offs.