Antennal responses of the German cockroach to select essential oil mixtures

The German cockroach, Blattella germanica (L.) is an important household insect pest. Homeowners turn to insecticides to control them. However, there have been problems with the use of insecticides. They can lead to the development of insecticide resistance. These factors have led to a paradigm shift from insecticides to essential oil components for controlling pests. Essential oils (EOs) are organic compounds produced by plants for defense and communication.  

The goal of this study was to investigate if B. germanica detects essential oil mixtures with its antennae. Electroantennogram studies were performed on an insecticide susceptible strain (S) and two multi-resistant strains (D and E) of B. germanica by recording their antennal responses after exposure to puffs of five different essential oil mixtures (Ecovia-EC, Essentria all-purpose, ER-22, and Excite R) at different dosages. The average responses at concentrations of 1-1000 micrograms/microliter to Ecovia-EC, Essentria all purpose, ER-22, and Excite R ranged from 0.3-0.5 mV, 0.8-2.1 mV, 0.19-0.53 mV, and 0.0006-0.27 mV, respectively, by strain S, 0.54-0.8 mV, 1.2-3.1 mV, 0.19-0.53 mV, and 0.007-0.19 mV by strain D, and 0.15-0.53 mV, 1.85-4.25 mV, 0.076-0.28 mV, and 0-0.17 mV by strain E. The result indicates that essential oil mixtures rich in terpenes and terpenoids elicit higher responses than mixtures with low terpene and terpenoid contents. Future work will include testing the antennal responses of the three strains of B. germanica to each active ingredient of the oil mixtures. The knowledge gained will help to solve the puzzle of the mechanism(s) of repellency in insects.