Vertical distribution of Mexican rice borer (Lepidoptera : Pyralidae) larvae and tunnels in Lower Rio Grande Valley sugarcane

Vertical distribution patterns of Mexican rice borer, Eoreuma loftini (Dyar ), larvae and tunnels in Lower Rio Grande Valley sugarcane, Saccharum spp., were examined by stalk dissections in commercial sugarcane from late May u ntil early September (1992) or mid-October (1993). Larval age distributions were fairly stable throughout the sampling periods. with small larvae cons istently comprising a substantial portion of the larval population infestin g millable stalks. Meaningful differences in the vertical distributions of small, medium, and large larvae were not detected. Contrary to earlier repo rts, most larvae and tunnels were located in the lower, more productive int ernodes regardless of the degree of stalk development. These results do not support the concept of age-specific internode susceptibility to Mexican ri ce borer attack, and stress the need to consider season-long population sup pression in the development of strategies to manage the Mexican rice borer in sugarcane.