Essential Oils: Useful Tools in Storage-Pest Management

Ruta Angustifolia Essential Oil: Behavioral and Insecticidal Effects Against Larvae and Adults of Tribolium castaneum

The study aims to evaluate the behavioral and insecticidal effects of Ruta angustifolia EO (RAEO) against larvae and adults of a major pest insect, Tribolium castaneum. RAEO exhibited a strong repellency against both adults and larvae where percentages as high as 74 and 72 % of PR (Percentage of Repellency) were recorded respectively, at 0.47 μL/cm2 after 2 h. Regarding the antifeedant bioassay, no feeding deterrence was recorded in adults while an increase in appetite was registered in larvae exhibiting -80 % of FDI recorded at 0.2 μL/pellet. In terms of feeding preference, the response significantly depended on the developmental stage (F=97.19, P<0.05) and larvae were attracted to treated pellets recording percentages of 84 and 73 % of PI (Preference index) after 5 and 30 min at 0.05 μL/pellet; on the other hand, adults expressed a repulsive behavior at 0.2 μL/pellet with a PI of -81.1 (20 min), and -69.2 % (30 min). Regarding topical application toxicity, a significant difference was observed between larvae and adults (p<0.05 F=174.56). The study promotes the use of RAEO as a repellent and bioinsecticide for the control of larvae and adults of T. castaneum.

Main Chemical Components, Activity and Mechanism of Repellence of Cyperus esculentus Essential Oil Against Tribolium confusum

Tribolium confusum is a major stored-product pest that exhibits resistance to chemically synthesized pest repellents. This study investigated the potential of essential oil (EO) extracted from the roots of Cyperus esculentus as a natural alternative for pest management. The EO was obtained through steam distillation, and its chemical composition was elucidated using gas chromatography-mass spectrometry. The primary compounds, cyperotundone and cyperene, were further isolated from the EO through silica gel column chromatography. The efficacy of the EO and its isolated compounds as pest repellents was evaluated against a flaxseed pest, which was identified as T. confusum through DNA sequence analysis. The results demonstrated that at 86.12 μg/cm2, the EO and its two main components maintained significant repellent activity for up to 24 h. In contrast, the effectiveness of the positive control, N, N-diethyl-3-methylbenzamide (DEET) declined rapidly after 8 h. At 16 h, the repellent activity of the EO and one of its main components, cyperotundone, was significantly greater than that of DEET. Furthermore, at a lower concentration of 43.06 μg/cm2, cyperotundone's repellent activity was significantly stronger than DEET's at 16 h. Additionally, cyperotundone outperformed DEET significantly from 4 to 16 h at 21.53 μg/cm2 and at 16 h at 10.76 μg/cm2. Among the two compounds, cyperotundone exhibited a longer-lasting repellent effect compared to cyperene, which is consistent with the lower evaporation rate of cyperotundone. Biochemical assays revealed that exposure to the EO of C. esculentus and its major compounds significantly reduced (p < 0.05) the activities of acetylcholinesterase and glutathione-S-transferase in T. confusum. Molecular docking experiments indicated that the compounds could bind to olfactory receptors with low binding energies. qRT-PCR analysis revealed that the EO and its two compounds significantly altered (p < 0.05) the expression levels of odorant receptor genes in the pest. These findings suggest that the repellent action of C. esculentus EO and its major compounds on T. confusum may be mediated through the modulation of the pest's olfactory system, as well as by inhibiting essential enzymatic activities in the pests. This research contributes valuable insights into the development of sustainable, long-lasting, and eco-friendly pest repellents, harnessing the potential of the rich botanical resource C. esculentus.

Towards Sustainable Pest Management: Toxicity, Biochemical Effects, and Molecular Docking Analysis of Ocimum basilicum (Lamiaceae) Essential Oil on Agrotis ipsilon and Spodoptera littoralis (Lepidoptera: Noctuidae)

Over the last decade, essential oils (EOs) have become potential ingredients for insecticide formulations due to their widespread availability and perceived safety. Therefore, this study aimed to evaluate the toxicity and biochemical efficacy of basil (Ocimum basilicum) (Lamiaceae) against two destructive pests Noctuidae, Agrotis ipsilon (Hufnagel) and Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). In addition, a molecular docking study was performed to gain insight into the binding pattern between glutathione S-transferase (GST) and linalool, the main component of EO. GC-MS analysis of O. basilicum EO revealed that linalool is the most abundant compound (29.34%). However, the toxicity tests showed no significant difference between the values of LC50 of O. basilicum EO to A. ipsilon and S. littoralis. On the other hand, the sublethal experiments indicated that treating the second instar larvae with LC15 or LC50 values of O. basilicum EO significantly prolonged the larval duration in both insects, compared to the control. Regarding the biochemical effect of O. basilicum EO, the treatments significantly impacted the activity of detoxification enzymes. A notable elevation in glutathione S-transferase (GST) activity was recorded in A. ipsilon larvae compared with a reduction in S. littoralis larvae. The molecular docking analysis revealed that linalool bonded with the amino acid serine (SER 9) of GST, indicating its binding affinity with the enzyme. The obtained results could offer valuable insights into the mode of action of O. basilicum and can encourage the adoption of sustainable pest control practices that incorporate essential oils.

Exploring the Efficacy of Four Apiaceae Essential Oils against Nine Stored-Product Pests in Wheat Protection

The Apiaceae family, known for aromatic plants producing bioactive essential oils (EOs), holds significance across sectors, including agrochemicals. This study evaluated the insecticidal potential of four Apiaceae EOs from Crithmum maritimum L., Trachyspermum ammi (L.) Sprague ex Turrill, Smyrnium olusatrum L., and Elwendia persica (Boiss.) Pimenov and Kljuykov against various significant storage pests (Sitophilus oryzae (L.), Trogoderma granarium Everts, Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), T. confusum Jacquelin du Val, Oryzaephilus surinamensis (L.), Alphitobius diaperinus (Panzer), Acarus siro L., and Tenebrio molitor L.) on wheat. Insect mortality rates were monitored at intervals of 1, 2, 3, 4, 5, 6, and 7 days. Smyrnium olusatrum EO exhibited the highest efficacy, followed by T. ammi, C. maritimum, and E. persica EOs, although efficacy varied by species, developmental stage, and concentration. Notably, complete mortality occurred for several pests at 1000 ppm of S. olusatrum and T. ammi EOs. Gas chromatography-mass spectrometry (GC-MS) analysis revealed key compounds in these EOs, including myrcene, germacrone, and curzerene in S. olusatrum EO, and thymol, γ-terpinene, and p-cymene in T. ammi EO. These findings emphasize their potential as botanical insecticides. Smyrnium olusatrum and T. ammi EOs emerge as promising eco-friendly pest management options due to their efficacy, highlighted compound composition, and availability of biomass from both wild and cultivated sources.

A Proximal Sensor-Based Approach for Clean, Fast, and Accurate Assessment of the Eucalyptus spp. Nutritional Status and Differentiation of Clones

Several materials have been characterized using proximal sensors, but still incipient efforts have been driven to plant tissues. Eucalyptus spp. cultivation in Brazil covers approximately 7.47 million hectares, requiring faster methods to assess plant nutritional status. This study applies portable X-ray fluorescence (pXRF) spectrometry to (i) distinguish Eucalyptus clones using pre-processed pXRF data; and (ii) predict the contents of eleven nutrients in the leaves of Eucalyptus (B, Ca, Cu, Fe, K, Mg, Mn, N, P, S, and Zn) aiming to accelerate the diagnosis of nutrient deficiency. Nine hundred and twenty samples of Eucalyptus leaves were collected, oven-dried, ground, and analyzed using acid-digestion (conventional method) and using pXRF. Six machine learning algorithms were trained with 70% of pXRF data to model conventional results and the remaining 30% were used to validate the models using root mean square error (RMSE) and coefficient of determination (R²). The principal component analysis clearly distinguished developmental stages based on pXRF data. Nine nutrients were accurately predicted, including N (not detected using pXRF spectrometry). Results for B and Mg were less satisfactory. This method can substantially accelerate decision-making and reduce costs for Eucalyptus foliar analysis, constituting an ecofriendly approach which should be tested for other crops.

Current Trends for Lavender (Lavandula angustifolia Mill.) Crops and Products with Emphasis on Essential Oil Quality

Lavender is in the research spotlight due to its increasing economic importance, while market demand is expected to continue to grow. Among the hundreds of essential-oil-bearing plants, Lavandula angustifolia Mill. remains one of the most valuable. This paper explores the lavender chain timeline from crop to products, examining the expanding knowledge on the characteristics, phytochemical profile and functional potential of lavender that could lead to new products and uses. Lavender crops can be expanded without competing for productive land, instead using marginal, contaminated or unproductive land. A novel cultivation trend proposes leveraging agri-background biodiversity, arbuscular mycorrhiza and the natural enemies of pests for healthy crops. Together with breeding efforts targeting highly performant genotypes with complex volatile profiles coupled with resistance to specific biotic (particularly Phytoplasma) and abiotic (salt, heavy metals) stressors, industry could have a steady supply of high-quality raw material. Besides the expansion of the uses of essential oil in cosmetics, pharmaceuticals, food and environmental and agri-applications, novel channels have appeared for the use of the solid by-product, which is rich in polyphenols and polysaccharides; these channels have the potential to create additional streams of value. The stabilization and optimization of techno-functional delivery systems through the encapsulation of essential oil can extend shelf-life and enhance biological activity efficiency.