Chemical composition of Deverra scoparia essential oil under different drying conditions and its insecticidal properties against Parlatoria blanchardi (Hemiptera: Diaspididae).

Abstract

Parlatoria blanchardi Targ. (Hemiptera: Diaspididae) is a destructive scale insect that causes serious damage to date palm plantations. The essential oil (EO) of Deverra scoparia Coss. & Durieu was investigated for its insecticidal activity against P. blanchardi under different drying methods. This is the first time to our knowledge that the insecticidal activity against P. blanchardi has been reported for the plant species D. scoparia. This study evaluates, for the first time, the bioactivity of D. scoparia EO, as well as its insecticidal activity against P. blanchardi under different drying techniques (air drying, sun drying, and microwave drying at 264, 400, and 800 W). The chemical composition of D. scoparia EO was identified and characterized using gas chromatography mass spectrometry (GC-MS). In addition, the responses of the target enzyme acetylcholinesterase (AChE) and 2 key detoxification enzymes, carboxylesterase (CarE) and glutathione S-transferase (GST), in P. blanchardi were investigated to elucidate the underlying mechanisms of toxicity. Our data showed that a total of 32 compounds were identified, with myristicin (43.44% to 69.73%), D-limonene (6.61% to 12.57%), dillapiole (0.74% to 10.87%), α-phellandrene (0.47% to 8.16%), and α-pinene (4.36% to 8.10%) as the dominant constituents. Insecticidal activity varied markedly with drying technique; microwave drying at 264 W produced the most toxic EO against adult stages (LC50 = 0.12 to 0.13 µl/ml), while sun-dried EO showed the highest efficacy against immature stages. Enzyme assays revealed that microwave-derived oils significantly increased AChE activity while strongly suppressing CarE and GST activities. Our findings suggest that this plant might be efficient as a potential alternative control agent for P. blanchardi.