Role of Varietal Resistance in Managing the Rice Water Weevil, a Major Insect Pest of Louisiana Rice

Abstract

Resistance of several commercial rice varieties widely grown in Louisiana was assessed against the rice water weevil (Lissorhoptrus oryzophilus Kuschel), the major insect pest of rice in the United States. A five-year field study was conducted to identify resistant genotypes among conventional inbred, herbicide tolerant, conventional hybrid, and herbicide tolerant hybrid varieties. Resistance was evaluated in two different locations to enable selection of rice varieties with wide adaptability over diverse environments. There were no large differences in the resistance found amongst commercial rice varieties over the five-year field study. Jefferson was frequently found to support lower larval densities than other varieties, while Jupiter often supported higher larval densities. Another assessment involved greenhouse experiments that evaluated adult preference for oviposition and survivorship of larvae on different varieties. Numbers of weevil eggs per plant differed significantly among varieties in choice tests but not in no-choice tests, while 1st instar densities in both choice and no-choice tests showed no significant differences between varieties. This suggests that inconsistency of oviposition preferences exist among the varieties. Nevertheless, analysis of mature instar data from the no-choice test showed that numbers of mature instars were significantly different among the varieties “Cheniere”, “CL111”, “CL151”, “Cocodrie”, “Jefferson”, and “Jupiter”. Percentage of larval survival showed no statistical difference between the four varieties tested. Our results from the field and the greenhouse suggest that none of the commercial varieties tested showed high levels of resistance to rice water weevil infestation, although Jupiter appears to be more susceptible than other varieties and Jefferson appears to be somewhat more resistant.