<p>High level of host specificity is a strength in considering gall-inducing insects in weed biological-management campaigns. The effects of gall-inducing insects on plants are subtle and discreet and are rarely quantified to establish their value in biological management. The Tephritidae (Diptera), Curculionidae (Coleoptera), and some Lepidoptera are effective in regulating populations of herbaceous weeds, mainly because of their specialized level of host relations and the irreversible damage they inflict upon host plants by interrupting water and nutrient transport. By injuring the plant and by draining the nutrients, these insects inflict minor to moderate levels of stress in the tissues and organs they infest, in addition to strongly impacting plant-resource availability and allocation. The more-widely used Cecidomyiidae (Diptera) are relatively less efficient in inflicting plant damage, leading to plant death. Gall-inducing insects are parasitic organisms that utilise host tissues for nutrition and habitat; they rarely cause direct and widespread mortality in weeds. Rather, because of their strength as monophagous-plant feeders, they can be used as primary plant stressors to downgrade plant immunity levels and deplete resources that contribute to either maintaining or enhancing fitness. Target weeds most likely require additional stressors, such as plant–plant competition or introduction of a necrotrophic or a phytotoxin-producing fungus to deliver whole-plant death. We propose a novel framework, establishing the specific impacts of gall-inducing insects on plant-resource allocation, to permit future research to be more explicit about how gall-inducing insects can contribute to effective biological-management outcomes.</p>