Introduction

The control of pests that cause losses in livestock production is usually accomplished with the use of commercial insecticides. Most products no longer present the expected efficacy due to a high level of parasitic resistance (Freitas 2008). The misuse of some insecticides not only shortens the life of the compound but also contaminates the environment. Among these parasites, flies are considered very important vectors of diseases since they may carry some pathogens such as bacteria, viruses, fungi, and parasites (Béjar et al. 2006).

Flies land on organic materials and other contaminated sites, infecting farm animals when in contact with them (Béjar et al. 2006). Besides contaminating, bites of bloodsucking flies cause pain and discomfort to animals (Palavesam et al. 2012). These factors stress the animals affecting their ideal weight gain and production. The specie Musca domestica which belongs to the family Muscidae, popularly known as house fly, is the most common fly to invade residences. Its presence is considered a sign of an unhygienic environment (Srinivasan et al. 2008). It feeds on decomposing waste material and is considered a vector of pathogens for humans and animals. House flies contaminate food and domestic utensils leading to the development of diseases in human and animals (Sangmaneedet et al. 2005), besides transporting the eggs of other parasites (Ugbogu et al. 2006). The M. domestica has also been considered responsible for the transmission of mastitis to livestock (Vazirianzadeh et al. 2008; Lamiaa et al. 2007).

Along with lower production, farmers have to spend more money by using inefficient chemical treatments, which may require multiple applications, increasing parasitic resistance, and environmental contamination. In this context, aiming the reduction of environmental damage and costs, many researchers are testing new herbal products (Chagas 2004). Some essential oils are already in use against flies, such as citronella oil (Chagas et al. 2002; Cárcamo et al. 2007), neem oil (Deleito and Borja 2008; Pissinati et al. 2009), andiroba oil, and tea tree oil (Klauck et al. 2014). Other essential oils such as bergamot, palmarosa grass, vetiver grass, and red cedar oil, have shown medicinal and antiparasitic properties, but they were not tested against house flies so far.

Bergamot (Citrus bergamia) oil derives from its peel, and it has linalyl acetate, limonene (Moufida and Marzouk 2003; Merle et al. 2004) and linanol as the main chemical compounds. The latter is considered an important antimycobacterial and antifungal agent (Romano et al. 2005; Kim et al. 2008). Fisher and Phillips (2008) have obtained satisfactory results using bergamot oil against bacteria. The palmarosa oil comes from a species of aromatic grass called cympobogon martini (Akhila 2009). Its main constituents are geraniol and geranyl acetate (Hong et al. 2011). The geraniol is found in oils such as citronella, and it has different therapeutic properties, such as high antimicrobial activity (Duarte et al. 2007; Jirovetz et al. 2007), antifungal activity (Duarte et al. 2005), and insect repellent activity (Makhaik et al. 2005; Kumar et al. 2007). Vetiveria zizanioides, popularly known as vetiver grass, is a perennial grass of approximately 1.50–2.20 m in height (De Castro and Ramos 2003). The essential oil of vetiver, besides anti-oxidant and anti-inflammatory activity, also has repellent activity against mosquitoes Aedes aegypti (Chou et al. 2012; Nuchuchua et al. 2010). Aarthi and Murugan (2010) showed in laboratory the efficiency of using vetiver oil as an insecticide against malaria’s vector mosquito. In a similar experiment, Amer and Mehlhorn (2006b) observed larvicidal and repellent activity of red cedar (Juniperus virginiana) essential oil. Red cedar, as popularly known, is a shrub that belongs to the family Cupressaceae. It is rich in monoterpene hydrocarbons, which have the potential to control parasitosis without environmental contamination (Cavaleiro et al. 2003). Due to the aforementioned, the aim of this study is to evaluate the in vitro insecticidal effect of bergamot, palmarosa, vetiver, and red cedar essential oil against the house fly.

Material and methods

Essential oils

Four essential oils were evaluated regarding their insecticidal activity against house flies. The oils were from four plants: red cedar (Juniperus communis), palmarosa grass (Cymbopogon martinii), vetiver grass (V. zizanioides), and bergamot (Citrus aurantium var. bergamia). Three different concentrations (1, 5, and 10%) were tested. Triton X-100 and distilled water were used as diluents (1 v/v) (Pazinato et al. 2014). The essential oils of red cedar, palmarosa grass, and vetiver grass were acquired from BioEssencia®. The essential oil of bergamot was acquired from Phytoterápica®.

Flies acquisition and bioassays with essential oils

Adult house flies were captured with the aid of a sweep net. They were collected from a farm on the city of Chapecó, SC, Brazil. After captured, the flies were housed in suitable cages with iron structure coated with a 20 × 20 × 30 cm thin nylon mesh. Water and food (sugar) were available all the time, up to the date of the tests (48 h of adaptation to the environment).

Testing cages were developed using plastic bottles of 2 l. The bottle ends were replaced by a thin mesh according to the methodology described by Klauck et al. (2014). A total of 780 flies were assigned into groups of 20 insects, for testing by aspersion (100 μL/group) with bergamot, palmarosa grass, vetiver grass, and red cedar oils at concentrations of 1, 5, and 10%. A control group was also used in which distilled water was added to the diluent oil (Triton 10%). The tests were performed in triplicate.

The results of the insecticidal effect were obtained by counting the number of dead flies at pre-determined time intervals: 30, 60, 90, 120, and 180 min, as well as 4, 5, 6, 7, and 8 h after the beginning of the experiment.

Statistical analysis

A parametric test was used to analyze the collected data, since the normality test was positive. Data concerning the insecticidal effect were statistically analyzed by the Duncan test. Significance was set at P < 0.05.

Results

The results of the in vitro insecticidal activity with the essential oil of bergamot are presented in Fig. 1a. At the concentration of 1%, bergamot oil showed no insecticidal effect. On the other hand, at 5% a large amount of flies was killed. When used in higher concentrations, bergamot essential oil was effective after 2 h of exposure, and reduced 73% of the number of live flies in the first 8 h.

Fig. 1
figure 1

Insecticidal action of essential oils from bergamot (a), palmorosa (b), vetiver (c), and red cedar (d) in the concentrations of 1, 5, and 10% against Musca domestica. The number of live flies was quantified in pre-determined periods of time, i.e., 30 min, as well as 1, 1:30, 2, 2:30, 3, 4, 5, 6, 7, and 8 h (**P < 0.01 and *P < 0.05)

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Palmarosa essential oil (Fig. 1b) at 5 and 10% showed insecticidal activity on the first 30 min of the experiment. However, the effectiveness of the 5% oil was 15% higher than the concentration of 10%. The 1% essential oil showed response different from the control group after 6 h of action.

There was no significant difference between the vetiver essential oil (Fig. 1c) at a concentration of 1% and the control group. Nonetheless, at 10% and after 1 h of action, this oil showed insecticidal effect, being able to eliminate 75% of the flies after 8 h. The concentration of 5% started eliminating flies only after 3 h of observation.

For the red cedar essential oil (Fig. 1d) at 1%, there was no significant difference compared to the control group concerning insecticidal efficiency. At a concentration of 10%, it was observed an 89% reduction of the number of flies after 8 h of the experiment. Although the efficiency was lower, a 5% solution had significant effect after 6 h of action.

A different effect was observed for different oils at the same concentrations (5 or 10%) (Fig. 2). At 5% (Fig. 2a) and after 6 h of experiment, the insecticidal effect of all essential oils was significantly different from the control group. After 30 min of study, the palmarosa oil caused high mortality of flies when compared to the control and to the other oils, but showed no significant difference at the end of the experiment. Comparing the oils at the highest concentration, 10% (Fig. 2b), Red cedar oil showed the greatest insecticidal effect. At least one of the oils showed significant results in comparison to the control group at every evaluated point. After 6 h of experiment, all essential oils presented insecticidal effect.

Fig. 2
figure 2

Insecticidal effect of essential oils from bergamot, palmorosa, vetiver grass, and red cedar in concentrations of 5 (a) and 10% (b) against Musca domestica. The number of live flies was quantified in pre-determined periods of time, i.e., 30 min, as well as 1, 1:30, 2, 2:30, 3, 4, 5, 6, 7, and 8 h (**P < 0.01 and *P < 0.05)

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Discussion

Essential oils of bergamot, palmarosa grass, vetiver grass, and red cedar showed an insecticidal effect against house flies (M. domestica). The lack of work reporting the use of these four oils studied justify this study since they are natural products with potential use to control M. domestica, an important vector of diseases to both humans and animals. Other oils have proven insecticidal effect, e.g., andiroba oil (Farias et al. 2009; Klauck et al. 2014) and tea tree oil (Klauck et al. 2014). The application of essential oils on different species of flies has already been studied. Cárcamo et al. (2007) reported that the essential oil of citronella at a concentration of 1% reduces 58.68% of the first-stage larvae of Lucilia sericata. The same study describes lower pupae weight when the larvae are exposed to different concentrations of citronella oil. Klauck et al. (2014) obtained 100% efficiency when testing the essential oils of the andiroba and tea tree in concentrations of 1 and 5% against horn flies (Haematobia irritans). In an analogous study, Agnolin et al. (2010) obtained results similar to ours by using the essential oil of citronella in the concentration of 5% against H. irritans.

Aarthi and Murugan (2010) used vetiver oil to control larvae of the malaria vector Anoplheles stephensi and observed a reduction of 85% in the amount of the larval stages II, III, and IV. This behavior explains the insecticidal potential of this oil, which was also found in this study, where the insecticidal effect on adult flies has been verified.

Amer and Mehlhorn (2006a, b) found the larvicidal action of red cedar oil against the third-stage larvae of A. aegypti as well as a repellent action against adult mosquitoes of the species A. aegypti and Culex quinquefasciatus. These results show that the oils studied have potential control action against parasites. In order to test the potential larvicidal activity against two species of mosquitoes (A. aegypti and Culex pipiens pallens) in the fourth-stage larvae, Lee (2006) tested 11 aromatic oils. Among these, red cedar and bergamot oils showed significant results. Lee (2006) reported 100% mortality rate at the concentration of 100 ppm and 40.5% at the concentration of 25 ppm when applying the red cedar oil. The bergamot oil showed 100% mortality rate at a concentration of 25 ppm, demonstrating the efficacy of the oil against mosquito larvae. Bergamot oil at lower concentrations (12.5 and 6.25 ppm) leads to mortality of 32.5 and 24.2%, respectively. Cosimi et al. (2009) evaluated the repellent action of bergamot oil in environmental pests. It was confirmed against maize weevil (Sitophilus zeamais), adult rusty grain beetle (Cryptolestes ferrugineus (Stephens)), and larvae of the mealworm beetle (Tenebrio molitor L).

Studies on the pesticide action of palmarosa oil have been performed by Kumar et al. (2007) in stored grain infested by beetles (Callosobruchus chinensis and Tribolium castaneum). In addition to significant effect on oviposition, development, and mortality of adult C. chinensis, this oil showed a powerful fumigant action and an effective repelling action in grain. Some compounds present in the essential oils are able to penetrate into fly tissues, modifying their physiological functions (Ozaki et al. 2003). According to the authors Regnault-Roger et al. (2012), the compounds exert their activities on insects through neurotoxic effects involving several mechanisms, notably through GABA, octopamine synapses, and the inhibition of acetylcholinesterase. The aforementioned results suggest that the essential oils studied may be used as components of repellents and insecticides. We conclude that the essential oils of bergamot, palmarosa grass, vetiver grass, and red cedar have insecticidal activity against M. domestica, although we did not determine their mechanisms of action. Therefore, these products may be used as an alternative to traditional drugs in the control of flies. That is because much of the traditional antiparasitic chemicals have low efficiency, mainly due to parasitic resistance. Another important point would be the toxic effects of these chemicals for the environment, which reinforces that essential oils have promising use in the near future. we did not determine their mechanisms of action.