A lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), larval attractant from peanut (Arachis hypogaea L. variety ‘Florunner’) plants was collected and determined using Tenax collection, cryogenic collection, olfactory bioassay, and infrared gas analyzer. All tests used larvae (third-fifth instar). Samples collected with a Tenax column did not induce significant olfactory responses by the larvae in the doses tested. In a cryogenic collection system using liquid nitrogen, plant volatiles were allowed to simultaneously pass through different treatments (air, water, activated carbon, or KOH) before they were cryogenized. After the airflow carrying volatiles from underground peanut plant parts was passed through water or activated carbon, the attractiveness was not significantly changed compared with the nonadsorption-treated collection. The attractiveness was totally eliminated after the airflow (carrying volatiles) was bubbled through KOH solution, indicating that the active component had been absorbed before being cryogenized. Cryogenically collected air, to a certain extent, was attractive to the larvae, indicating that an active component existed in normal air but the concentration was not high enough to attract the larvae. Among cryogenic collection samples, only those maintaining high carbon dioxide concentration were attractive to lesser cornstalk borer larvae. Lesser cornstalk borer larvae were attracted to commercial carbon dioxide. No significant difference in lesser cornstalk borer attraction was detected between 4 g of peanut root and a combination of urea and urease with similar carbon dioxide-releasing rate. It is concluded that lesser cornstalk borer larvae use carbon dioxide from underground peanut plant parts as a primary guide for locating the host plants.