Monday, 18 November 2002

This presentation is part of : Student Competition Display Presentations, Section B. Physiology, Biochemistry, Toxicology, and Molecular Biology

Catnip, Nepeta cataria (Lamiaceae), a close look: Comparative repellents and seasonal ecology

Gretchen Schultz, Erica Simbro, Jason Belden, Junwei Zhu, and Joel Coats. Iowa State University, Department of Entomology, Ames, IA

Recent research in botanical essential oils has supported repellency folklore. Evidence of repellent properties in catnip, or catmint surfaced in preliminary studies. This study compared catnip essential oil from steam distillation to current commercial repellents. These comparative studies found the catnip steam distillate to be as good, and in some cases better, at repelling house flies, Musca domestica, and American cockroaches, Periplaneta americana, than DEET or citronellal. A more specific repellency bioassay assessing the repellency of Z,E nepetalactone, the major constituent of catnip essential oil, showed it was significantly more repellent than DEET and citronellal. Since previous studies show the E,Z nepetalactone isomer to be even more repellent than Z,E, this study also examined the seasonal variation of Z,E and E,Z nepetalactone. Samples of fresh catnip were collected and divided as mature leaves, immature leaves, and stems, which were then steam distilled separately. Isomer composition was analyzed using HPLC. An ANOVA analysis showed significant differences due to week and week/plant part interaction. The mature leaf essential oil samples were tested in a repellency bioassay and exhibited significant repellency to German cockroaches, Blattella germanica. Attempts to identify a relationship between percent repellency and Z,E:E,Z nepetalactone ratio were inconclusive. Analysis of the volatiles released from catnip flowers was also conducted, as well as a record of phytophagous insects and pollinators. GC/MS showed the presence of Z,E nepetalactone, E,Z nepetalactone and b-caryophyllene as the major constituents of the floral volatiles.

Species 1: Blattaria Blattellidae Blattella germanica (German cockroach)
Species 2: Blattaria Blattidae Periplaneta americana (American cockroach)
Species 3: Diptera Muscidae Musca domestica (house fly)
Keywords: Catnip, Repellent

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