The role of host plants on the population dynamics of the rice stink bug, Oebalus pugnax (F.)

The rice stink bug, Oebalus pugnax (F.), is an important late season pest of rice in all rice producing south of the United States. Rice stink bugs are graminaceous feeders, but prefer to feed on rice at heading to grain maturity, resulting in yield loss and poor grain quality.  The importance of host plants to the buildup of rice stink bug populations before dispersal to rice fields has not been sufficiently studied. The relative abundance and polyphagy/host sequence of rice stink bug was studied weekly from May – August each year in 2011 and 2012 using a 38 cm sweep-net in the Mississippi Delta, MS. Three counties were surveyed. We found that the distribution and abundance of host plants directly impacted the local distribution and abundance of rice stink bug populations. More than thirteen wild host and two cultivated host plants were listed. Glyphosate resistant annual Italian ryegrass supported high populations of rice stink bugs from winter emergence into early June when peak densities were observed. The abundance, distribution and sequence of host flowering greatly enhanced the reproductive biology of rice stink bugs. In 2011, rice stink bug mean density per 10 sweeps per host was more than twice the normal threshold limit set for rice, compared to 2012 which was lower than threshold limit. Early control measures on these grasses may reduce rice stink bug population and subsequent injury in rice. Higher temperatures above 80ºF were a critical factor in regulating rice stink bug population.