Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2011
Publication Date: 7/1/2011
Citation: Showler, A.T., Beuzelin, J.M., Reagan, T.E. 2011. Alternate crop and weed host plant oviposition preferences by the Mexican rice borer (Lepidoptera: Crambidae). Crop Protection. 30(7):895-901. Interpretive Summary: While a number of alternative weed and crop hosts of the Mexican rice borer, a major pest of sugarcane in Texas, have been reported, the extent to which they might support Mexican rice borer populations is unknown. This greenhouse-based study compared egg laying preference for five graminaceous weed species, and for crop hosts sugarcane, sorghum, and corn. Preference among the weeds was greatest for sudangrass, and corn was the most preferred crop host; mechanisms for observed preferences are discussed. This is the first report indicating the likely importance of corn to Mexican rice borer populations.
Technical Abstract: The Mexican rice borer, Eoreuma loftini (Dyar), is the key pest of sugarcane, Saccharum hybrids, in south Texas, having largely displaced the sugarcane borer, Diatraea saccharalis (F.), and it is moving into rice- and sugarcane-growing areas of east Texas and Louisiana. While a number of alternative weed and crop hosts have been reported, the extent to which they might support Mexican rice borer populations is unknown. This greenhouse-based study involving choice assays compared oviposition preference for and larval infestations of five graminaceous weed species, and assessed levels of infestation between crop hosts sugarcane and corn, Zea mays L., and between corn and sorghum, Sorghum bicolor (L.) Moench. We determined that the average number of larval entry holes in sudangrass stems was '2.5-fold more than any of the other four weed host plants, that corn had '5.9-fold more larval entry holes than sorghum, and '8.2-fold more than sugarcane. Greater oviposition and infestation of one weed host over another was not related to numbers of stems per plant, but was instead associated with the greater stem diameter and abundance of dry leaf tissue found in sudangrass, Sorghum vulgare Hitchc.; johnsongrass, S. halapense (L.); and barnyardgrass, Echinochloa crus-galli (L.) P. Beauv.; relative to the other weed species in this study. In terms of the crop host plants, stalk diameter and quantity of dry leaf tissue were not associated with numbers of eggs or larval entry holes in the choice assays between corn and sorghum, and between sugarcane and corn. While corn has been known as a host of the Mexican rice borer for at least 84 years, its role in area-wide population dynamics and control efforts has likely been greatly underestimated.