Fumigant toxicity and antifeedant effects of rosemary essential oil against the flour beetle, Tribolium confusum

The flour beetle (Tribolium confusum du Val) is one of the most important coleopteran pests on stored products, especially cereal grains and flour. Frequent application of chemical pesticides in insect pest management has resulted in numerous side effects such as environmental contamination, threat to human health and non-target organisms, and the development of pest resistance. In the present study, the fumigant toxicity and anti-nutritional effects of rosemary essential oil on flour beetle adults were investigated. Due to the relationship between the chemical compositions of essential oils with their biological effects, the compounds of rosemary essential oil were studied by gas chromatography-mass spectrometry. Rosemary essential oil was rich in terpenic compounds, including the hydrocarbon monoterpenes (28.72%), monoterpenoids (57.03%), hydrocarbon sesquiterpenes (3.09%), and sesquiterpenoids (3.25%). The concentration of 73.5 µl/l air of essential oil caused 90.0% mortality of the pest after 24 h, which was increased to 100% by 48 h. The use of 24-h LC₄₀ and LC₅₀ values of essential oil, respectively equal to 26.7 and 35.5 µl/l air, reduces the nutritional indices of the pest, including consumption index, relative consumption rate, and relative growth rate after 5 and 10 days. In addition, the feeding deterrence index of the mentioned values was estimated at 40.7 and 45.9% after 5 days and 53.4 and 59.5% after 10 days, respectively. Therefore, rosemary essential oil can be introduced as one of the available and efficient agents in the management of flour beetle for further research.