Essential oils of cinnamon, turmeric and neem as potential control agents against home-invading acid flies (Paederus fuscipes) and darkling beetles (Luprops tristis)

Objectives Paederus fuscipes and Luprops tristis constitute Kerala's two most notorious home-invading arthropod pests. To control their infestations, indoor application of pesticides is commonly practiced, which is detrimental to human health and the environment. This study explores the bioactive properties of plant essential oils as a control agent against them. Methods We analyzed the constituents of oils, their repellence, and fumigant toxicity against P. fuscipes and L. tristis. The constituents and the bioactive compounds in oils were analyzed using Gas Chromatography-Mass spectroscopy analysis. For the evaluation of the repellence activity of the plant essential oils- two choice bioassays were performed, where the control was treated with acetone, and the test contained a mixture of oil in acetone (0.1 µl/cm2). Fumigant toxicity of oils was done by no choice bioassay (0.1 µl/ml air). To determine the potency of the oils, lethal concentration 50 (LC50) was determined; LC50 refers to the concertation of a substance in the air required to kill 50 % of the test animals over a period of time. LC50 of cinnamon oil no choice assay with 0.04 µl/ml, 0.06 µl/ml, 0.08 µl/ml, 0.1 µl/ml and 1.2 µl/ml concentration was performed. Results Of the three plant essential oils, turmeric oil was the best repellent against both P. fuscipes (86.66 ± 11.54) and L. tristis (40 ± 20). Cinnamon oil showed the highest activity as a fumigant with 100 % and 73.33 ± 46.18 % mortality in P. fuscipes and L. tristis after 8 h of exposure. The analysis of the constituents indicated the presence of over 63 different chemical compounds in the three oils. The three plant essential oils tested showed insect deterrent activity, with turmeric oil as the best repellent and cinnamon oil as the best fumigant against pests. Conclusions The activities shown were significant enough to be used to replace/add to the conventionally used pesticides, especially in indoor settings. These oils in themselves or by isolating the specific compounds could pave the way to developing more effective and greener pest control methods.