Catnip essential oil as a barrier to subterranean termites (Isoptera: Rhinotermitidae) in the laboratory

The essential oil of catnip, Nepeta cataria (Lamiacae) was evaluated for behavioral effects on two populations of subterranean termite, Reticulitermes flavipes (Kollar) and R. virginicus (Banks) (Isoptera: Rhinotermitidae). The catnip essential oil contained approximately 36:64 E,Z-nepetalactone and Z,E-nepetalactone, respectively. The time to 50% dissipation (DT50) of the isomers in sand was dependent on dose, and ranged from 5.7 to 12.6 d for the E,Z-isomer and 7.7-18.6 d for the Z,E-isomer. For R. flavipes, the 24-h topical LD50 value was approximately 8200 microg/g termite. The 24-h fumigation LC50 value for R. flavipes was between 36 and 73 microg/ml air, and the 7-d fumigation LC50 value was between 14 and 36 microg/ml air. Exposure of R. virginicus to treated sand resulted in a 24-h LC50 value (95% F.L.) of 84 (67.6, 112) microg/cm2 and a 7-d LC50 value of 21.1 (16.4, 26.8) microg/cm2; for R. flavipes these values were 63.2 (53.7, 73.9) and 44.4 (34.6, 58.1) microg/cm2, respectively. Vertical tunneling through treated sand was eliminated at 500 ppm for R. virginicus and at 250 ppm for R. flavipes. Horizontal tunneling was stopped at 250 ppm for R. virginicus and reduced at doses above 250 ppm for R. flavipes. Although tunneling ceased in these tests, mortality was not high, indicating that the termites avoided the treated sand. Efficacy of catnip oil was equivalent to other monoterpenoids reported in the literature.