The effect of host weed phenology, abundance, and diversity and natural enemies on the population dynamics of the southern green stink bug, Nezara viridula (L.), in Hawaiian macadamia orchards was investigated. We found that the highest kernel damage occurred immediately following abrupt reductions in the flowering and fruiting stages of host weeds. Areas with the greatest diversity of host weeds showed higher damage, presumably because of higher N. viridula population levels. Predation rates on sentinel egg masses were highest over the two seasons in areas where the bigheaded ant, Pheidole megacephala (F.), comprised a large portion of the ant fauna. In one of the orchards, P. megacephala and the longlegged ant, Anoplolepis longipes (Jerdon), occurred in a spatial mosaic where the boundaries shifted back and forth over time. Sentinel egg masses placed in these two adjacent areas showed predation rates were highest in the areas dominated by P. megacephala, and intermediate in the interface zone and lowest where only A. longipes were found. The importance of weed phenology and natural enemy induced mortality is discussed.