The Impact of Planting Date on Management of the Rice Water Weevil in Louisiana Rice

Abstract

The rice water weevil, Lissorhoptrus oryzophilus, is the most destructive insect pest of rice in the United States. Early planting of rice to avoid damaging infestations of the rice water weevil has long been suggested as a management tactic. A five-year study was conducted to characterize the influence of rice planting date on rice water weevil manage- ment in light of recent trends toward earlier planting of rice in Louisiana. Experimental designs differed among years: ex- periments in 2001 and 2008 were split-plot studies, whereas in 2003, 2004, and 2007, separate randomized block experi- ments were conducted. Results from these experiments showed that early planting of rice facilitated rice water weevil management in three ways. Weevil infestations were lighter in rice planted in mid- to late March than in later-planted rice in three of five years of the study. In addition, yield losses attributable to weevil feeding were lower in early planted rice than in late planted rice in the two split-plot experiments. Finally, single applications of lambda-cyhalothrin (a pyrethroid applied to rice after flooding to kill weevil adults) were less effective in late planted rice than in early planted rice. This study demonstrates that early planting can serve as an important component of a management program for rice water wee- vils in Louisiana.