Lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae), larval injury to the root-hypocotyl region of greenhouse-reared ‘Florunner’ peanut, Arachis hypogaea L., plants was investigated by determining the size and distribution of feeding sites. The percent injury to periderm, cortex, phloem, and xylem tissues also was estimated. Tissue loss due to insect feeding was measured for only the most prominent of several wound sites on each stem axis. Percent injury to principal tissues was estimated by planimetric methods.

The lesser cornstalk borer caused significant injury to the periderm, cortex, and the phloem on mainstems of peanut plants. Mean percent injury was 31.67% for the periderm and cortex, 16.78% for phloem, and only 0.19% for the xylem. Approximately 91% of all feeding sites occurred on the mainstem or were contiguous with the mainstem and a branch. The frequently of plants with feeding sites declined linearly with increasing number of sites. These data support the hypothesis that root growth declines with increasing larval injury to phloem and xylem (food and water conducting tissues, respectively) in the root-hypocotyl region.