Interactive Impacts of Rice Water Weevil1 and Sheath Blight Pathogen on Rice Yield

Abstract

In the southern US, rice, Oryza sativa L., is frequently attacked simultaneously by rice water weevil, Lissorhoptrus oryzophilus Kuschel, and sheath blight pathogen, Rhizoctonia solani J.G. Kuhn. Field studies were used to determine the impact of L. oryzophilus infestation on development of sheath blight and combined effects of both L. oryzophilus and R. solani on yield of rice cultivars, ‘Cocodrie’ and ‘Jefferson’. Infestation by L. oryzophilus had no influence on severity of sheath blight in either Cocodrie or Jefferson. Grain yield of both cultivars was significantly less in response to infestation by L. oryzophilus. Infection by R. solani alone significantly reduced yield only in the susceptible cultivar Cocodrie. Percent yield losses in Cococdrie in response to exposure to L. oryzophilus and R. solani alone and in combination were 5.6, 23.9, and 20.0%, respectively. Similarly, percent yield losses in Jefferson in response to exposure to L. oryzophilus and R. solani alone and in combination were 7.3, 10.6, and 5.4%, respectively. Combined impact of infestation by L. oryzophilus and infection by R. solani on yield did not differ significantly from the impact of pathogen infection alone in Cocodrie. The combined impact of R. solani and L. oryzophilus on yield in Jefferson did not vary significantly from the impact of either alone. Results suggested that L. oryzophilus did not affect severity of sheath blight in rice, and the combined impact of L. oryzophilus and R. solani on rice yield was less than additive. Understanding the interaction between L. oryzophilus and R. solani, important pests of rice in the southern US, will help manage these pests more effectively.