Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2010
Publication Date: 10/1/2010
Citation: Brown, M.W., Mathews, C.R., Krawczyk, G. 2010. Extrafloral nectar in an apple ecosystem to enhance biological control. Journal of Economic Entomology. 103(5):1657-1664. Interpretive Summary: Development of sustainable agricultural production will require sustainable pest management options. Biological control is one of the major methods for sustainable pest control. To make biological control more effective, farms need to supply food and shelter to make the beneficial insects better able to lower pest abundance. In this paper, we provide additional food in the form of nectar producing glands on peach trees. Laboratory studies tested the effect of nectar on the effectiveness of a parasitic insect on an apple pest, and field trials tested the response of parasitic insects on pest abundance. The nectar was found to increase parasite longevity and parasitism rates, but field tests did not show any change in parasitism rates in the orchard. Although parasitism was not increased in the field, additional data showed that scale and stink bug damage to fruit was decreased in the presence of peach nectar. The results demonstrate that the addition of peach nectar to apple orchards does make pest management more sustainable. This information will be used by orchard pest control specialists and scientists investigating habitat modification for increasing biological control in orchards and other agricultural settings.
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.