Sterile insect technique (SIT) is periodically releasing mass-reared sterile insects to control target pests by impeding their successful reproduction. In Okinawa Prefecture, Japan, the SIT is currently applied against West Indian sweet potato weevil which is a flightless agricultural pest of sweet potato. We examined effects of spatiotemporal evenness of sterile insect releases on regional eradication of the pest with limited mobility, by constructing a simple two-patch population model. We found that spatially biased sterile insect releases seriously inhibited regional pest eradication even if a large number of sterile insects released with short intervals. However, we also found that temporally balancing the spatially biased releases could greatly improve the negative effect and promote regional pest eradication. We illustrated that these outcomes were caused by too low mobility of the target insect. This study revealed that limited mobility of target pests crucially inhibits regional pest eradication due to spatiotemporally biased releases of sterile insects. Accordingly, we conclude that spatiotemporally even releases of sterile insects are requisite for regional eradication of less mobile pests, such as West Indian sweet potato weevil, irrespective of the other release strategies. Effects of limited mobility on outcomes of the SIT have rarely been argued in previous theoretical studies. Thus, we could provide new insights into how sterile insects should be released especially against less mobile pests.