Exotic wildland weeds serve as reservoirs for a newly introduced cole crop pest, B agrada hilaris ( H emiptera: P entatomidae)

The role of wildland weeds that serve as alternate hosts for insect pests has not been directly examined for the potential to sustain pest populations or facilitate pest outbreaks. The development of weed biological control programmes is also complicated by weed species that are closely related to economically important or native plants, especially rare or special status species. In recent surveys in southern C alifornia, USA , we found a newly introduced insect pest of cole crops, B agrada hilaris B urmeister ( B agrada bug) , feeding on B rassicaceae weeds in riparian areas adjacent to agricultural fields where cole crops are routinely grown. Insect populations grew to levels well over action thresholds and caused severe damage to populations of the invasive weed, L epidium latifolium (perennial pepperweed). The numerical response of B . hilaris on L . latifolium and other B rassicaceae weeds in natural areas may pose a significant challenge to effectively managing pest populations in crops. However, the accidental introduction of this insect provides the opportunity to examine plant–insect interactions with important implications for development of biologically based control methods for weeds.