Insect Repellent Lemongrass

Introduction

The stable fly Stomoxys calcitrans L. is among the most damaging arthropod pest of livestock worldwide, with a high economic impact on dairy and beef cattle production. It is also a potential mechanical vector of animal pathogens such as equine infectious anemia virus, Trypanosoma evansi, and Besnoitia besnoiti. Control of stable fly populations includes various methods, such as chemical control (pesticides and repellents), cultural control (sanitation), mechanical control (trapping devices), and biological control (parasitoids and entomopathogenic fungi). The best approach is the simultaneous use of several methods in an integrated pest-management program. Management of adult flies is accomplished mainly with topical insecticides, applied directly to animals. However, continued or repeated use of conventional insecticides often results in the development of resistance and fosters serious human health and environmental concerns. Populations of S. calcitrans resistant to pyrethroids and/or organophosphates have already been described in North America and in Europe. As a result, there have been increased research efforts for natural and environmentally friendly repellents, particularly those based on essential oils. Several plant-based repellents, such as citronella oil, eucalyptus oil, catnip oil, and zanthoxylum oil, have previously been tested against stable flies and have shown a reduction in attraction and in feeding. These repellents can be applied topically on animals or in livestock barns. The first study demonstrating the potential application of a plant-based repellent was conducted by Zhu et al., in which wax-based catnip pellets spread in the manure/soil areas of cattle feedlots resulted in over 99% repellency of stable flies.

Lemongrass oil is the essential oil obtained from the aerial parts of Cymbopogon citratus (DC.) Stapf., Poaceae. Geranial (α-citral) and neral (β-citral) are the two main active components of lemongrass oil, but other compounds, such as geraniol and citronellol, which are known repellents, are also present in small amounts]. Lemongrass essential oil has previously shown a repellent effect, alone or in combination, against different species of disease-transmitting mosquitoes (Diptera: Culicidae) and the house fly Musca domestica L. (Diptera: Muscidae), and is already present in commercially available products. Therefore, our objectives were to verify the sensitivity of antennal receptor cells of S. calcitrans to lemongrass oil and to evaluate its repellency against stable flies using a video-tracking system.