Wednesday, December 16, 2009: 8:32 AM
Room 101, First Floor (Convention Center)
Different habitat types in agricultural landscapes, such as crops and native vegetation, can have different functions for arthropod herbivores and their natural enemies. In this study we quantified crop colonization by herbivores and natural enemies from native vegetation. We established plots of sentinel cotton seedlings in native vegetation, fields adjacent to native vegetation, and fields at least 400 m from native vegetation in two experimental landscapes. We used plants infested with Helicoverpa armigera (cotton bollworm) egg cards and Bemisia tabaci (silverleaf whitefly) nymphs to quantify the effectiveness of natural enemies, and uninfested plants to assess pest colonization. Parasitism of whitefly nymphs was significantly higher in native vegetation and fields adjacent to native vegetation than fields far from native vegetation, but this was not consistent across all patches of native vegetation. Predation rates of Helicoverpa eggs on cotton plants were not significantly different among the three treatments. As for pests, proximity to native vegetation did not significantly influence colonization by aphids, thrips, Helicoverpa spp. or leaf hoppers. Whiteflies typically colonized sentinel plants in the fields, but not in native vegetation. These findings show that native vegetation can be a source habitat for natural enemies but not for pests. On-farm conservation of biodiversity can therefore contribute to more sustainable crop production systems, which are less reliant on the use of chemical pesticides.