Abstract Tomato leafminer (TLM), Phthorimaea absoluta Meyrick, and the potato tuber moth (PTM), Phthorimaea operculella (Zeller), are significant invasive pests with similar ecological niches, investigated interspecific competition and reproductive interference of TLM and PTM on 2 host plants the species have in common, tobacco and potato. In cage experiments PTM replaced TLM after 2 successive generations on tobacco and TLM replaced PTM after 3 generations on potato. In tobacco experiments, PTM did not significantly affect the oviposition of TLM. Conversely, TLM presence stimulated PTM oviposition: PTM egg-laying was significantly higher in groups exposed to female TLM adults (110.81 ± 7.59 eggs/female) or male TLM adults (112.17 ± 5.87 eggs/female) compared to the PTM-only control group (90.81 ± 4.89 eggs/female). In potato experiments, there were no significant differences among treatments. In tobacco greenhouse experiments, when TLM was in the presence of PTM, the number of F1 adults of TLM decreased significantly. In the presence of TLM, there was a significant increase in the number of PTM adults in the F1 generation. In potato greenhouse experiments, our results showed no significant differences in the counts of F1 generation adults or the sex ratio. Interspecific interactions were asymmetric depending on the host plant. On tobacco, PTM exhibited stronger competitiveness and was able to displace TLM. However, on potato, TLM displaced PTM, indicating a stronger competitive ability of TLM on that host. These results demonstrate the importance of context, including host plant or other environmental conditions, when assessing the potential strength and direction of interspecific interactions.