Toxicity and synergistic activity of compounds from essential oils and their effect on detoxification enzymes against Planococcus lilacinus

Abstract

Mealybug, Planococcus lilacinus Cockerell, is a primary surface-feeding insect pest of fruit and flowering plants and also transmits plant viruses, resulting in economic crop loss. Inappropriate and recurrent use of pesticides for mealybug control results in resistance building and deleterious effects on humans and the environment. Essential oils are the most excellent choice for insecticides. Insecticidal activities of pure compounds of essential oils against P. lilacinus are not reported. The present study aims to study the insecticidal activities of some pure active compounds and their binary mixture’s action by topical application against P. lilacinus. Results showed that the pure compounds of L-limonene, β-myrcene, and ocimene revealed toxicity (each at LD50 = 0.37 µg/insect) after 96 h. The binary mixtures of geraniol + L-menthol and L-limonene + geraniol exhibited synergistic effects (each at LD50 = 0.03 µg/insect) after 96 h. The monoterpenes of ocimene and β-myrcene at the higher concentration of 5,000 ppm substantially inhibited the detoxification enzyme activities of AChE (0.93 and 0.78 mU/mg, respectively) and GST (2.19 and 7.29 nmol/min/ml, respectively) in P. lilacinus after 48 h. SEM analysis reported the significant anomalies on the morphology of abdominal cuticle, setae, and thoracic leg after 96-h treatment with ocimene at 1,250 ppm against P. lilacinus. Based on the results, the tested pure compounds and their combinations can be suggested for the control of mealybugs.

Termiticidal, biochemical, and morpho-histological effects of botanical based nanoemulsion against a subterranean termite, Odontotermes Formosanus Shiraki

“…Nevertheless, prior research on the structural abnormalities brought on by Tagetes minuta L. oil against A. craccivora , and Plutella xylostella (Linnaeus, 1758) was scarce and substantially corroborated the current study’s findings ( Dolma et al., 2022 ; Jayaram et al., 2022 ). Also the ocimene-treated Planococcus lilacinus (Cockerell, 1905) showed multiple abnormalities on the setae, thoracic leg, and cuticle (body fluid accumulation and thickness encrustations) ( Arokiyaraj et al., 2022 ). According to findings from other authors ( Botas et al., 2017 ; Pessoa et al., 2018 ), A. aegypti and C. quinquefasciatus larvae showed modifications in the cuticle of the head, thorax, abdomen, and siphon when treated with various nanoemulsions.…”

Mentha spp. Essential Oils: A Potential Toxic Fumigant with Inhibition of Acetylcholinesterase Activity on Reticulitermes dabieshanensis

“…Similarly, Pavela [41,42] demonstrated that the binary mixtures of carvone and linalool resulted in synergistic effects on the adult mortality of Spodoptera littoralis and C. quinquefasciatus, respectively. Additionally, ocimene strongly synergized the toxicity of β-myrcene, L-limonene, geraniol, and L-menthol against Planococcus lilacinus [43]. In addition, the study of Prasannakumar et al [30] revealed that the combined use of 4-carene and α-pinene was very effective against Phthorimaea absoluta.…”

Cupressus sempervirens Essential Oil, Nanoemulsion, and Major Terpenes as Sustainable Green Pesticides against the Rice Weevil

“…The bioactivity of plant oils are attributed to several components, with demonstrable insecticidal activity contained in the plant EO, especially in monoterpenes such as αpinene, α-terpinene, limonene, camphor, carvacrol, thymol, δ-3-carene, α-thujone, 1,8-cineol (eucalyptol), eugenol, and ascaridole [3,6,[9][10][11]17,57]. Although a synergism with other minor constituents is common where each oil component participates in penetration, fixation, and distribution into biomembranes [6,9,17], synergy between components of an EO might be occur between several components contained in the same oil, or between different essential oils with known biological activities [17,64,65].…”