Novel hosts can incur fitness costs to a frugivorous insect pest.

In phytophagous insects, adult attraction and oviposition preference for a host plant are often positively correlated with their immature fitness; however, little is known how this preference-performance relationship changes within insect populations utilizing different host plants. Here, we investigated differences in the preference and performance of two populations of a native North American frugivorous insect pest, the plum curculio ( Conotrachelus nenuphar )-one that utilizes peaches and another that utilizes blueberries as hosts-in the Mid-Atlantic United States. We collected C .  nenuphar adult populations from peach and blueberry farms and found that they exhibited a clear preference for the odors of, as well as an ovipositional preference for, the hosts they were collected from, laying 67%-83% of their eggs in their respective collected hosts. To measure C .  nenuphar larval performance, a fitness index was calculated using data on larval weights, development, and survival rate from egg to 4th instars when reared on the parent's collected and novel hosts. Larvae of C .  nenuphar adults collected from peach had high fitness on peach but low fitness when reared on blueberry. In contrast, larvae from C .  nenuphar adults collected in blueberry had high fitness regardless of the host on which they were reared. In this study, we show that utilizing a novel host such as blueberry incurs a fitness cost for C .  nenuphar from peaches, but this cost was not observed for C .  nenuphar from blueberries, indicating that the preference-performance relationship is present in the case of insects reared on peach, but insects reared on blueberry were more flexible and able to utilize either host, despite preferring blueberry.