Fumigant toxicity of lemon eucalyptus oil constituents to acaricide-susceptible and acaricide-resistant Tetranychus urticae

Current Situation of Tetranychus urticae (Acari: Tetranychidae) in Northern Africa: The Sustainable Control Methods and Priorities for Future Research

In North Africa, Tetranychus urticae Koch, 1836 represents one of the most destructive generalists among mite herbivores. Unfortunately, it is a source of important annual casualties in crop production. It is a phytophagous mite that can feed on hundreds of host plants and produces significant damage. The control of T. urticae in North Africa has been principally based on acaricide sprays. However, new alternative methods have shown effective results, such as artificial ultraviolet-B, natural enemies, and the introduction of new genetic methods. This review aims to present a synthesis of information surrounding control methods of T. urticae in North Africa. We highlight the principal findings of previous studies. Then, we discuss current control methods and propose new innovative research and sustainable approaches to controlling this pest. The control method can potentially extrapolate in North African regions due to its positive ecological results. Further, studies proved the use of natural enemies, myco-metabolites, bacteria metabolites, and the introduction of a genetic method in an integrated long-term sustainable program that can successfully defeat the populations of T. urticae. We also discuss high-priority research guidelines to investigate new sustainable management strategies. Setting up an integrated long-term ecological monitoring program in different Northwest African countries and incorporating new technologies into monitoring programs is an urgent need to fight this devastating pest.

Green Micro- and Nanoemulsions for Managing Parasites, Vectors and Pests

The management of parasites, insect pests and vectors requests development of novel, effective and eco-friendly tools. The development of resistance towards many drugs and pesticides pushed scientists to look for novel bioactive compounds endowed with multiple modes of action, and with no risk to human health and environment. Several natural products are used as alternative/complementary approaches to manage parasites, insect pests and vectors due to their high efficacy and often limited non-target toxicity. Their encapsulation into nanosystems helps overcome some hurdles related to their physicochemical properties, for instance limited stability and handling, enhancing the overall efficacy. Among different nanosystems, micro- and nanoemulsions are easy-to-use systems in terms of preparation and industrial scale-up. Different reports support their efficacy against parasites of medical importance, including Leishmania, Plasmodium and Trypanosoma as well as agricultural and stored product insect pests and vectors of human diseases, such as Aedes and Culex mosquitoes. Overall, micro- and nanoemulsions are valid options for developing promising eco-friendly tools in pest and vector management, pending proper field validation. Future research on the improvement of technical aspects as well as chronic toxicity experiments on non-target species is needed.

Botanicals Against Tetranychus urticae Koch Under Laboratory Conditions: A Survey of Alternatives for Controlling Pest Mites

Tetranychus urticae Koch is a phytophagous mite capable of altering the physiological processes of plants, causing damages estimated at USD$ 4500 per hectare, corresponding to approximately 30% of the total cost of pesticides used in some important crops. Several tools are used in the management of this pest, with chemical control being the most frequently exploited. Nevertheless, the use of chemically synthesized acaricides brings a number of disadvantages, such as the development of resistance by the pest, hormolygosis, incompatibility with natural predators, phytotoxicity, environmental pollution, and risks to human health. In that sense, the continuous search for botanical pesticides arises as a complementary alternative in the control of T. urticae Koch. Although a lot of information is unknown about its mechanisms of action and composition, there are multiple experiments in lab conditions that have been performed to determine the toxic effects of botanicals on this mite. Among the most studied botanical families for this purpose are plants from the Lamiaceae, the Asteraceae, the Myrtaceae, and the Apiaceae taxons. These are particularly abundant and exhibit several results at different levels; therefore, many of them can be considered as promising elements to be included into integrated pest management for controlling T. urticae.

Identification of Insecticidal Constituents from the Essential Oil from the Aerial Parts Stachys riederi var. japonica

The essential oil of Stachys riederi var. japonica (Family: Lamiaceae) was extracted by hydrodistillation and determined by GC and GC-MS. A total of 40 components were identified, representing 96.01% of the total oil composition. The major compounds in the essential oil were acetanisole (15.43%), anisole (9.43%), 1,8-cineole (8.07%), geraniol (7.89%), eugenol (4.54%), caryophyllene oxide (4.47%), caryophyllene (4.21%) and linalool (4.07%). Five active constituents (acetanisole, anisole, 1,8-cineole, eugenol and geraniol) were identified by bioactivity-directed fractionation. The essential oil possessed fumigant toxicity against maize weevils (Sitophilus zeamais) and booklice (Liposcelis bostrychophila), with LC₅₀ values of 15.0 mg/L and 0.7 mg/L, respectively. Eugenol and anisole exhibited stronger fumigant toxicity than the oil against booklice. 1,8-Cineole showed stronger toxicity, and anisole as well as eugenol exhibited the same level of fumigant toxicity as the essential oil against maize weevils. The essential oil also exhibited contact toxicity against S. zeamais adults and L. bostrychophila, with LC₅₀ values of 21.8 µg/adult and 287.0 µg/cm², respectively. The results indicated that the essential oil of S. riederi var. japonica and its isolates show potential as fumigants, and for their contact toxicity against grain storage insects.

α-Terpineol, a natural monoterpene: A review of its biological properties

Terpineols are monocyclic monoterpene tertiary alcohols which are naturally present in plant species. There are five common isomers of terpineols, alpha-, beta-, gamma-, delta- and terpinen-4-ol, of which α-terpineol and its isomer terpinen-4-ol are the most common terpineols found in nature. α-Terpineol plays an important role in the industrial field. It has a pleasant odor similar to lilacs and it is a common ingredient in perfumes, cosmetics, and aromatic scents.

In addition, α-terpineol attracts a great interest as it has a wide range of biological applications as an antioxidant, anticancer, anticonvulsant, antiulcer, antihypertensive, anti-nociceptive compound. It is also used to enhance skin penetration, and also has insecticidal properties. This study reviews the relevance of α-terpineol based on scientific findings on Google Scholar, Pubmed, Web of Science, Scopus and Chemical Abstracts.

Collectively, the use of α-terpineol in medicine and in the pharmaceutical industry plays an important role in therapeutic applications. This review will, therefore, support future research in the utilization of α-terpineol.

Formulation and characterization of garlic (Allium sativum L.) essential oil nanoemulsion and its acaricidal activity on eriophyid olive mites (Acari: Eriophyidae)

Green and nanoacaricides including essential oil (EO) nanoemulsions are important compounds to provide new, active, safe acaricides and lead to improvement of avoiding the risk of synthetic acaricides. This study was carried out for the first time on eriophyid mites to develop nanoemulsion of garlic essential oil by ultrasonic emulsification and evaluate its acaricidal activity against the two eriophyid olive mites Aceria oleae Nalepa and Tegolophus hassani (Keifer). Acute toxicity of nanoemulsion was also studied on male rats. Garlic EO was analyzed by gas chromatography-mass spectrometry (GC-MS), and the major compounds were diallyl sulfide (8.6%), diallyl disulfide (28.36%), dimethyl tetrasulfide (15.26%), trisulfide,di-2-propenyl (10.41%), and tetrasulfide,di-2-propenyl (9.67%). Garlic oil nanoemulsion with droplet size 93.4 nm was formulated by ultrasonic emulsification for 35 min. Emulsification time and oil and surfactant ratio correlated to the emulsion droplet size and stability. The formulated nanoemulsion showed high acaricidal activity against injurious eriophyid mites with LC₅₀ 298.225 and 309.634 μg/ml, respectively. No signs of nanoemulsion toxicity were noted in treating rats; thus, it may be considered non-toxic to mammals. Stability of garlic oil nanoemulsion, high acaricidal activity, and the absence of organic toxic solvents make the formulation that may be a possible acaricidal product. Results suggest the possibility of developing suitable natural nanoacaricide from garlic oil.

Chemical Variability and Biological Activities of Eucalyptus spp. Essential Oils

Many plant species produce mixtures of odorous and volatile compounds known as essential oils (EOs). These mixtures play important roles in Nature and have been utilized by mankind for different purposes, such as pharmaceuticals, agrochemicals, aromatherapy, and food flavorants. There are more than 3000 EOs reported in the literature, with approximately 300 in commercial use, including the EOs from Eucalyptus species. Most EOs from Eucalyptus species are rich in monoterpenes and many have found applications in pharmaceuticals, agrochemicals, food flavorants, and perfumes. Such applications are related to their diverse biological and organoleptic properties. In this study, we review the latest information concerning the chemical composition and biological activities of EOs from different species of Eucalyptus. Among the 900 species and subspecies of the Eucalyptus genus, we examined 68 species. The studies associated with these species were conducted in 27 countries. We have focused on the antimicrobial, acaricidal, insecticidal and herbicidal activities, hoping that such information will contribute to the development of research in this field. It is also intended that the information described in this study can be useful in the rationalization of the use of Eucalyptus EOs as components for pharmaceutical and agrochemical applications as well as food preservatives and flavorants.

Kazakh Ziziphora Species as Sources of Bioactive Substances

Ziziphora species represent the prototypical example of the Lamiaceae family. The phytochemicals present in Ziziphora include monoterpenic essential oils, triterpenes and phenolic substances belonging to the flavonoids. In Kazakh traditional medicine, Ziziphora species possess several medicinal uses. In particular, Z. bungeana Lam. and Z. clinopodioides Lam. are used for the treatment of illnesses related to the cardiovascular system or to combat different infections. Unfortunately, the majority of the information about the complex Ziziphora species is only available in Russian and Chinese language, therefore, we decided gather all available information on Kazakhstan Ziziphora, namely its content compounds, medicinal uses and published patents, to draw the attention of scientists to this very interesting plant with high medicinal potential.

Ultrafine particle emissions from essential-oil-based mosquito repellent products

Ultrafine particle (UFP) emissions from three essential-oil-based mosquito repellent products (lemon eucalyptus (LE), natural insects (NI), and bite shield (BS)) were tested in a 386 l chamber at a high air exchange rate of 24/h with filtered laboratory air. Total particle number concentration and size distribution were monitored by a condensation particle counter and a scanning mobility particle sizer, respectively. UFPs were emitted from all three products under indoor relevant ozone concentrations (~ 17 ppb). LE showed a nucleation burst followed by a relatively stable and continuous emission while the other two products (NI and BS) showed episodic emissions. The estimated maximum particle emission rate varied from 5.4 × 10(9) to 1.2 × 10(12) particles/min and was directly related to the dose of mosquito repellent used. These rates are comparable to those due to other indoor activities such as cooking and printing. The emission duration for LE lasted for 8-78 min depending on the dose applied while the emission duration for NI and BS lasted for 2-3 h.

PRACTICAL IMPLICATIONS

Certain essential-oil-based mosquito repellents can produce high concentrations of UFPs when applied, even at low ozone levels. Household and personal care products that contain essential oil may need to be tested at indoor relevant ozone levels to determine their potential to increase personal UFP exposures.

Potential of eucalyptus oil as repellent against house rat, Rattus rattus

Rodent repellents are chemicals which by taste or odour or possibly by both will prevent animal from feeding or gnawing. Such substances may be used in protecting an area from rodent infestation or in protecting packaged food, packing materials, electric cables, and other important vulnerable materials. Mature and healthy house rat, Rattus rattus of both sexes, was exposed to 5, 10, and 20% eucalyptus oil applied as spray in laboratory pens in bichoice tests. Each concentration was applied through three different modes of application, that is, daily, once, and alternatively in a week. Repellent effect of the oil was assessed based on food consumption from treated and untreated sides for four days. In overall, food consumption was significantly (P < 0.0001) low from treatment side compared to the untreated side indicating significant repellent effect of the oil at all the three concentrations tested. Repellent effect of the oil was, however, not found to differ significantly between the two sexes. Percent repellency in both male and female rats was apparently more with daily application of 5 and 10% eucalyptus oil. Present studies reveal the potential of eucalyptus oil in repelling away R. rattus; however, further studies may be conducted to enhance the persistence of repellent effect for longer period of time.

Identification and field evaluation of non-host volatiles disturbing host location by the tea geometrid, Ectropis obliqua

Volatile organic compounds derived from non-host plants, Ocimum basilicum, Rosmarinus officinalis, Corymbia citriodora, and Ruta graveolens, can be used to mask host plant odors, and are repellent to the tea geometrid, Ectropis obliqua. Volatile compounds were collected by headspace absorption, and the components were identified and quantified by using gas chromatography/mass spectrometry. The responses of antennae of female E. obliqua to the compounds were evaluated with gas chromatography/electroantennography detection. Qualitative and quantitative differences were found among the four odor profiles. Consistent electroantennographic activity was obtained for eight of the volatiles from the four plants: β-myrcene, α-terpinene, γ-terpinene, linalool, cis-verbenol, camphor, α-terpineol, and verbenone. In a Y-tube bioassay, six chemicals, β-myrcene, γ-terpinene, (R)-(-)-linalool, (S)-(-)-cis-verbenol, (R)-(+)-camphor, and (S)-(-)-verbenone, were the main compounds responsible for repelling E. obliqua. An eight-component mixture including all of the bioactive compounds (in a ratio of 13:2:13:8:1:24:6:17) from R. officinalis was significantly more effective at repelling the moths than any single compound or a mixture of equal amounts of the eight compounds. Field results demonstrated that intercropping tea plants with R. officinalis effectively suppressed E. obliqua infestations in a tea plantation. Our findings suggests that odor blends of R. officinalis play a role in disturbing host orientation behavior, and in repelling E. obliqua adults, and that R. officinalis should be considered when developing "push-pull" strategies aimed at optimizing the control of E. obliqua with semiochemicals.

Eugenol--from the remote Maluku Islands to the international market place: a review of a remarkable and versatile molecule

Eugenol is a major volatile constituent of clove essential oil obtained through hydrodistillation of mainly Eugenia caryophyllata (=Syzygium aromaticum) buds and leaves. It is a remarkably versatile molecule incorporated as a functional ingredient in numerous products and has found application in the pharmaceutical, agricultural, fragrance, flavour, cosmetic and various other industries. Its vast range of pharmacological activities has been well-researched and includes antimicrobial, anti-inflammatory, analgesic, anti-oxidant and anticancer activities, amongst others. In addition, it is widely used in agricultural applications to protect foods from micro-organisms during storage, which might have an effect on human health, and as a pesticide and fumigant. As a functional ingredient, it is included in many dental preparations and it has also been shown to enhance skin permeation of various drugs. Eugenol is considered safe as a food additive but due to the wide range of different applications, extensive use and availability of clove oil, it is pertinent to discuss the general toxicity with special reference to contact dermatitis. This review summarises the pharmacological, agricultural and other applications of eugenol with specific emphasis on mechanism of action as well as toxicity data.