Technical Abstract: A common goal of conservation biological control is to enhance biodiversity to increase abundance and effectiveness of predators and parasitoids. Although many studies report an increase in abundance of natural enemies, it has been difficult to document increases in rates of biological control. To enhance parasitism of the leafroller, Platynota idaeusalis (Tortricidae), alternate food was provided by interplanting peaches that produce extrafloral nectar into apple orchards. Laboratory studies showed that the presence of nectar increased longevity and parasitism rates by its dominant parasitoid in West Virginia, Goniozus floridanus (Bethylidae). In orchard studies, we found the total number of Hymenopteran parasitoids was higher on peach trees than on adjacent apple trees. Abundance of Hymenoptera was also significantly higher on the side of traps facing away from rather than toward peach trees, supporting the attraction to peach trees producing extrafloral nectar. However, the total parasitism rates of P. idaeusalis were not affected by the presence of peach extrafloral nectar in any field studies. Insect injury to fruit at harvest showed that fruit from orchards with interplanted peach trees had less injury from San Jose scale (Quadraspidiotus perniciosus) and stink bugs (Pentatomidae) than fruit from an apple monoculture. Although the interplanting with peach trees did not have the expected result of increased biological control, the experiment did have beneficial results for pest management. These results demonstrate the importance of collecting data on variables beyond the targeted species when evaluating habitat manipulation experiments to fully assess the impact on the entire ecosystem.