Beneficial soil microbes as drivers of plant-insect interactions: a perspective

The association of plants with beneficial soil microbes, including arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria, can enhance plant growth and nutrient uptake while modifying plant traits, including growth rate, architecture, nutritional quality, secondary metabolites, phytohormones, and volatile organic compounds (VOCs), necessary for interactions with insect pests and their natural enemies. Microbe-induced effects on insect herbivores and their natural enemies can be positive, neutral, or negative, and are context-dependent, creating the need for continued synthesis of published research to identify emerging patterns, recognize limitations, and guide future research. This perspective highlights three key pathways through which beneficial soil microbes drive interactions among agricultural plants, insect pests, and their natural enemies through the lens of applied research: (1) alterations in plant growth rate, architecture, and nutritional quality; (2) modifications of plant secondary metabolites and phytohormones; and (3) modifications in the emissions of VOCs. Existing limitations, including inconsistent and context-dependent outcomes, are summarized, and future research areas are outlined. Finally, this perspective emphasizes the need to understand how crop breeding, domestication, and climate change-associated stressors, individually and in combination, shape the outcomes of these interactions. Addressing limitations will ensure that microbe-based pest management strategies become dependable tools that producers can use to reduce pesticide use, protect crops from biotic and abiotic stressors, and sustainably enhance crop productivity.