Insect herbivory remains a major constraint on agricultural productivity and ecosystem stability worldwide. Plants have evolved diverse structural, chemical, and inducible defense mechanisms that reduce herbivore damage while shaping ecological and evolutionary interactions across trophic levels. Beyond direct deterrence, plant defenses influence herbivore specialization, multitrophic interactions, and community structure, generating dynamic feedback between plants and insects. Although plant defense biology has been extensively examined from molecular and evolutionary perspective, there is potential need to explicitly connect these mechanisms to applied pest management frameworks. Here, we integrated structural barriers, secondary metabolite production, inducible signaling pathways, and herbivore-induced plant volatiles within a unified ecological context and examined how these traits influence herbivore performance, specialization, and adaptation. We further evaluated how plant defense traits can be incorporated into durable integrated pest management (IPM) strategies through selective breeding, a resistance trait pyramid, ecological intensification, and adaptive monitoring. By bridging mechanistic defense biology with ecological theory and agricultural implementation, this review summarized pathways for harnessing plant-based resistance to reduce insecticide reliance and promote resilient agroecosystems.