Host Fidelity Depends on Host Plant Quality in the Potato Tuber Moth

Host fidelity in phytophagous insects can arise from both genetic constraints and behavioral plasticity, with consequences for host specialization. The preference–performance hypothesis predicts that females should oviposit on hosts that maximize offspring fitness, yet the extent to which host fidelity and host quality jointly shape oviposition preference is not fully understood. For host fidelity to be an adaptive pattern, it should be relaxed in scenarios of low‐quality hosts. We used the potato tuber moth Phthorimaea operculella (PTM) to test if fidelity to a given host depends on its quality as larval host. First, PTM larvae were reared on seven potato ( Solanum tuberosum ) varieties differing in dry matter content. We measured performance parameters, including larval stage duration, pupal weight, and pupal survival. We found variation in PTM performance across potato varieties, which was aligned with the varieties dry matter content. Larval development was fastest and pupal numbers highest on the high‐dry matter (starchy) varieties, while pupal weight varied among varieties and did not consistently align with host quality. Based on the performance results, we chose one potato variety representing each of three categories of host quality: low (waxy), high (starchy) and intermediate (waxy‐starchy). Second, we evaluated in a four‐port olfactometer the oviposition preference of gravid females reared on each of those three varieties of different quality, having as alternative choices the same three varieties plus a control variety. Females reared on high‐quality and intermediate‐quality varieties strongly preferred their rearing host, that is, showed host fidelity. In contrasts, those females reared on a low‐quality variety showed no preference. Results show that host fidelity in PTM is conditional on host quality and shaped by developmental experience, supporting the preference–performance hypothesis when hosts are of relatively high quality only. Our findings have implications for the evolution of host specialization in insects and PTM management.