AN ABSTRACT OF THE
Steven H. Harwood
for the degree of Master of Science in Entomology
presented on December 14 I987,
Oregon State University
Title: Toxicity of Peppermint Monoterpenes to the Variegated Cutworm, Peridroma saucia
The toxicity of menthol, menthone, pulegone, limonene, and alpha-pinene, five monoterpenes
found in peppermint (Mentha piperita L.), to the variegated cutworm (Peridroma
saucia Hübner) was characterized by in vivo and in vitro methods.
Pulegone and menthone caused slower growth over
six days when incorporated into an artificial diet and fed to fifth stadium larvae.
Reduced growth was likely the result of the significant antifeedant properties observed
for these compounds.
Menthol, the dominant monoterpene found in peppermint leaves caused molting and pupation
inhibition when incorporated in the diet over the dosage range comparable to that found in
plants (0.05% to 0.2%). Limonene at a dose of 0.2% caused significant inhibition of
pupation, but otherwise had little effect on growth or survival. Alpha-pinene had no
effect on pupation, growth or survival over a dosage range of 0.05% to 0.2%.
All five monoterpenes were metabolized in vitro by the cytochrome P450 dependent
polysubstrate oxidase system, however piperonyl butoxide did not synergize their toxicity
in vivo. Neonate larvae were more sensitive to oral administration of these monoterpenes
than were fifth stadium larvae.
These experiments suggest that monoterpenes in
peppermint leaves could cause mortality to neonate variegated cutworm larvae.