Effects of Physical and Chemical Factors on Oviposition by Plodia interpunctella (Lepidoptera: Pyralidae)

Acceptance of a potential host for oviposition by gravid female moths is believed to be predominantly determined by the physical and chemical cues on the substrate surface. We evaluated the effects of substrate physical and chemical stimuli on oviposition by the Indianmeal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), in a series of laboratory experiments. The experimental arenas were 5.7-liter plastic boxes that contained a single, uncovered 5-cm-diameter glass petri dish with either artificial substrates alone or artificial substrates applied with 0.1 g-equivalent of a hexane extract of wheat, Triticum aestivum L., or 10 g of wheat kernels. Presence of the chemical extract of wheat significantly increased P. interpunctella oviposition compared with physical stimuli without extract. A dish surface with spherical glass beads elicited significantly enhanced oviposition compared with surfaces with cheesecloth, filter paper, or sandpaper. Increasing the numbers of similar-sized extract-treated glass beads increased oviposition until a certain number of beads was reached, after which the oviposition remained constant. The diameter of the spherical glass beads, rather than the total surface area of beads presented, significantly influenced oviposition, with the 5-mm-diameter glass beads receiving the most eggs. P. interpunctella oviposition was also affected by the geometric shape of substrates, with ovoid shapes preferred over cuboid. These studies clearly show that semiochemical and physical cues are required to elicit maximum oviposition by P. interpunctella, and they suggest that ovipositing females prefer substrates with smooth, round or curved contours.