Seasonal Abundance and Phenology of Oebalus pugnax (Hemiptera: Pentatomidae) on Graminaceous Hosts in the Delta Region of Mississippi

The rice stink bug, Oebalus pugnax (F.), is a graminaceous feeder, and the most injurious insect pest of heading rice, Oryza sativa L., in the United States. Rice growers are aware of the economic importance of host grasses in O. pugnax abundance. However, the need for increased knowledge of host sequence relative to O. pugnax abundance is vital. Densities of O. pugnax on 15 graminaceous hosts were evaluated in the central Mississippi Delta from April through August in 2011 and 2012. Two cultivated and 13 wild host grasses were sampled using a sweep net. Overall, populations of O. pugnax were lower in 2012 than in 2011. Italian ryegrass, Lolium perenne L. ssp. multiflorum (Lambert), was the main host that supported O. pugnax survival and reproduction from overwintering to early summer. Echinochloa spp., Digitaria spp., and Eriochloa spp. maintained greater populations of O. pugnax in the summer. Browntop millet, Urochloa ramosa (L.) Nguyen, and broadleaf signalgrass, U. platyphylla (Munro ex C. Wright) R. D. Webster, were important for populations of O. pugnax populations immediately prior to overwintering. Host switching was also an important factor that contributed to O. pugnax abundance. The evolution of Italian ryegrass resistance to the broad spectrum herbicide glyphosate in the central Mississippi delta has become an important component of O. pugnax population dynamics because of its increased abundance in and around agricultural areas. Cultural control measures on host grasses before flowering could result in less use of insecticides, thereby reducing cost of rice production.