The chinch bug, Blissus occiduus, has become an increasingly important pest of buffalograss Buchloë dactyloides and zoysiagrass Zoysia japonica. Although this chinch bug can be controlled with insecticides, the identification of turfgrasses with chinch bug-resistant traits would provide an alternative and environmentally-responsible approach for managing this important turfgrass pest. Germplasm screening studies have identified resistance to B. occiduus in several buffalograss (PX-3-5-1, 184, 196) and zoysiagrass (El Toro, Emerald, Zorro) cultivars. However, only limited information is available on the underlying mechanisms of this resistance. Of particular interest is the role played by oxidative enzymes in the defense response of buffalograss to chinch bugs. Previous studies have documented changes in peroxidase activity in resistant buffalograsses in response to chinch bug feeding. Chinch bug-infested resistant plants had higher levels of peroxidase activity when compared with their control plants, whereas peroxidase activities in control and infested susceptible plants remained unchanged or were slightly lower for infested plants. These results suggest that increases in peroxidases may accompany insect feeding in resistant genotypes. This increase could be an important marker for selecting resistant germplasm. This research further investigated the impact of chinch bug feeding on peroxidase activity levels in resistant and susceptible buffalograsses and zoysiagrasses.