Sublethal effects of oregano essential oil and its major compound carvacrol on biological parameters of Aedes albopictus (Diptera: Culicidae).

Mosquito management programs rely basically on the use of conventional synthetic larvicides. However, frequent applications and misuse of some synthetic insecticides have led to problems related to mosquito resistance development, harmful effects on human health and unacceptable environmental effects on non-target organisms. Recently, a growing number of phytochemicals has been tested as more eco-friendly larvicides against various mosquito species, exerting high efficacy with multiple modes of action. In the laboratory, we investigated for the first time the sublethal effects of oregano oil and its major compound carvacrol, against Aedes albopictus (Asian tiger mosquito), a mosquito of great medical importance. We determined the effects of short term (24h) exposure of 3rd- 4th larvae to LC50 concentrations on survival and development of survived larvae until adulthood, as well as on fecundity, fertility, longevity and wing length of emerged adults. Only half of 24h survived larvae from oregano oil and carvacrol treatment finally reached adulthood. Abnormal shapes of dead larvae and pupae, and failed adult emergence were also observed, indicating a potential growth inhibitory activity of the tested materials. No particular effects from exposure to larvicidal LC50 concentrations were recorded on life cycle parameters of successfully emerged adults. These findings suggest the tested oregano oil and carvacrol as sufficiently effective larvicides against Ae. albopictus at lower than the acutely toxic concentrations, promoting a more eco-friendly and less costly profile for these biopesticides.

Biocompatible colloidal dispersions as potential formulations of natural pyrethrins: a structural and efficacy study.

Biocompatible colloidal dispersions of the micro- and nanoemulsion type based on lemon oil terpenes, polysorbates, water, and glycerol were used for the formulation of pyrethrins, botanical insecticides derived from the white pyrethrum daisy, Tanacetum cinerariifolium. The proposed formulation is based on pyrethrin-containing water-in-oil (W/O) microemulsions that could be diluted in one step with an aqueous phase to obtain kinetically stable oil-in-water (O/W) nanoemulsions. Structural characteristics of the micro- and nanoemulsions were evaluated by electron paramagnetic resonance (EPR) spectroscopy, dynamic light scattering (DLS), small angle X-ray scattering (SAXS), and electrical conductivity. Dynamic properties of the surfactant monolayer as evidenced by EPR measurements were affected by the water content, the surfactant, and also the presence of the biocide. DLS and SAXS experiments of the nanoemulsions indicated the existence of two populations of oil droplets dispersed in the aqueous phase, globular droplets of 36-37 nm in diameter, and also larger droplets with diameters >150 nm. All of the applied techniques for structural determination revealed the participation of the biocide in the nanostructure. The insecticidal effect of the encapsulated natural pyrethrin was evaluated in laboratory bioassays upon a target-insect pest, the cotton aphid Aphis gossypii Glover (Hemiptera: Aphididae) in eggplant, and was found to be increased compared to the commercial pyrethrin formulation.

Insecticidal activity of plant essential oils against the vine mealybug, Planococcus ficus.

The vine mealybug, Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), is a pest in grape vine growing areas worldwide. The essential oils from the following aromatic plants were tested for their insecticidal activity against P. ficus: peppermint, Mentha piperita L. (Lamiales: Lamiaceae), thyme-leaved savory, Satureja thymbra L., lavender, Lavandula angustifolia Mill, and basil, Ocimum basilicum L. Essential oils from peels of the following fruits were also tested: lemon, Citrus limon L. (Sapindales: Rutaceae), and orange, C. sinensis L. The reference product was paraffin oil. Bioassays were conducted in the laboratory by using spray applications on grape leaves bearing clusters of P. ficus of one size class, which mainly represented either 3rd instar nymphs or pre-ovipositing adult females. The LC50 values for each essential oil varied depending on the P. ficus life stage but did not significantly differ between 3(rd) instar nymphs and adult females. The LC50 values of the citrus, peppermint, and thyme-leaved savory essential oils ranged from 2.7 to 8.1 mg/mL, and the LC50 values of lavender and basil oil ranged from 19.8 to 22.5 and 44.1 to 46.8 mg/mL, respectively. The essential oils from citrus, peppermint and thymeleaved savory were more or equally toxic compared to the reference product, whereas the lavender and basil essential oils were less toxic than the paraffin oil. No phytotoxic symptoms were observed on grape leaves treated with the citrus essential oils, and low phytotoxicity was caused by the essential oils of lavender, thyme-leaved savory, and mint, whereas the highest phytotoxicity was observed when basil oil was used.

Do Patches of Flowering Plants Enhance Insect Pollinators in Apple Orchards?

Apples depend on insect pollination but intensification of agriculture jeopardizes pollination services in agroecosystems. Concerns about the dependency of crop pollination exclusively on honey bees increase the interest in agricultural practices that safeguard wild pollinators in agroecosystems. The purpose of the study was to assess the potential of floral resource provision in apple orchards to enhance the conservation of hymenopterous pollinating insects and potentially the pollination service to the crop. For this reason, flowering plant mixtures sown in patches inside apple orchards were tested against wild plant patches. Pollinator taxa recorded on the sown and wild plant patches were honey bees, wild bees (Andrena, Anthophora, Eucera, Halictus, Lasioglossum, Megachilidae on both; Systropha only on wild plants; Bombus, Hylaeus, Sphecodes, Nomada, Xylocopa only on sown mixture), syrphids, bee flies. The most abundant pollinator of apple was A. mellifera but wild bees were also recorded (Andrena, Anthophora, Bombus, Xylocopa, Lasioglossum, Megachilidae). The sown mixture attracted a more diverse taxa of pollinators and in greater numbers compared to the weed flora, but it did not have an effect on pollinators visiting apple flowers. Groundcover management with patches of suitable flowering mixtures can enhance pollinator conservation in apple orchards.

Potential of Hedgerows with Aromatic Plants as Reservoirs of Natural Enemies of Pests in Orange Orchards.

In the present study, the potential of hedgerows from Mediterranean aromatic plant species, i.e., oregano, rosemary, sage, and savory, in orange field margins to function as reservoirs of natural enemies of citrus pests was tested in comparison to the common management practice of bare soil or weed vegetation. Assessments were based on the abundance and diversity of parasitoid wasps, spiders, and insect predators in the field margins and on the orange trees for two growing seasons. Savory plants harbored more parasitoids compared to weed vegetation and the other aromatic plants (savory > organic rosemary > sage > oregano). Weed vegetation hosted more arachnid predators than the aromatic plants in their first year in the orchard, but this was reversed with their full growth in the following year (most abundant on rosemary). Oregano and sage favor insect predators. The similarity of the natural enemy communities on the field margins and on the orange trees increased with time, indicating the insects' movement from the field margins to the trees. The results support the use of the tested aromatic plant species in conservation practices for targeted groups of beneficial arthropods in orange orchards, also considering the exploitation of suitable wild flowering plants of the weed flora.

Efficacy Evaluation of Oregano Essential Oil Mixed with Bacillus thuringiensis israelensis and Diflubenzuron against Culex pipiens and Aedes albopictus in Road Drains of Italy.

Mosquito management programs in the urban environment of Italian cities mainly rely on larval control with conventional insecticides, primarily targeting the road drains that constitute the principal mosquito breeding sites encountered in public. The repeated utilization of synthetic insecticides may have adverse effects on non-targets and lead to resistance development issues, while the performance of biopesticides encounters limitations in field use. Botanical insecticides as single larval control agents or in binary mixtures with conventional insecticides have been extensively studied in the laboratory as an effective and eco-friendly alternative mosquito control method with promising results. The study herein concerns the investigation, for the first time under realistic conditions in the field, of the joint action of a carvacrol-rich oregano Essential Oil (EO) with two conventional insecticides, namely, the insect growth regulator diflubenzuron and the bio-insecticide Bacillus thuringiensis israelensis (B.t.i.), in road drains in Crevalcore city, Italy, against Culex pipiens and Aedes albopictus. According to the obtained results, the application of both plain EO and its mixtures with diflubenzuron and B.t.i. exerted very high efficacy in terms of immature mosquito population reduction over a two-week period. Three weeks after treatment, the performance of the oil and its mixtures diminished but remained high, while the addition of diflubenzuron potentiated the persistent action of the oil against Cx. pipiens. These findings are indicative of the potential of mixing carvacrol-rich EO with diflubenzuron and B.t.i. as an efficient eco-friendly alternative to mono-insecticide applications in road drains against Cx. pipiens and Ae. albopictus larvae.

Practices to Conserve Pollinators and Natural Enemies in Agro-Ecosystems.

Intensive agriculture has put great pressure on populations of beneficial arthropods such as natural enemies and pollinators, especially through adverse effects of pesticide use and the impact on resources in the agricultural landscape, i [...].

Do pesticides promote or hinder sustainability in agriculture? The challenge of sustainable use of pesticides in modern agriculture.

Sustainable agriculture aims to meet the food needs of the growing world population while ensuring minimal impact on the environment and humans as well as productivity. Although pesticides represent the backbone of the agri-food sector in its endeavor to secure food production their application is perceived by many as an obstacle towards the achievement of sustainability; the main concerns are linked with their adverse effects on human health and the environment. Τhis review aims to present the status of chemical plant protection and provide insights into the use of pesticides within the context of sustainable agriculture. It mainly focuses on the strengthened legislation frameworks, which especially in the European Union and the United States of America ensure the placement in the market of pesticides with acceptable toxicological and environmental profiles without compromising crop production. Furthermore, the implementation of Integrated Pest Management principles plays a key role in the sustainable use of pesticides. The stringent regulatory requirements have resulted in the dramatic increase of the associated effort and costs in pesticide research and development (R&D) of improved products. Nevertheless, the investment of leading agrochemical companies in the R&D of new pesticides remains high. All the above set the ground for the sustainable use of pesticides in crop production while their successful application remains a challenge.

Sown Wildflowers Enhance Habitats of Pollinators and Beneficial Arthropods in a Tomato Field Margin.

We evaluated the capacity of selected plants, sown along a processing tomato field margin in central Greece and natural vegetation, to attract beneficial and Hymenoptera pollinating insects and questioned whether they can distract pollinators from crop flowers. Measurements of flower cover and attracted pollinators and beneficial arthropods were recorded from early-May to mid-July, during the cultivation period of the crop. Flower cover was higher in the sown mixtures compared to natural vegetation and was positively correlated with the number of attracted pollinators. The sown Glebionis coronaria, Coriandrum sativum, Anethum graveolens, and Fagopyrum esculentum attracted mainly wild bees, which were the most abundant pollinating insects. In the natural vegetation, Rapistrum rugosum attracted mainly honeybees, while Asteraceae, Convolvulaceae, and Apiaceae species attracted wild bees. Beneficial arthropod abundance and diversity were higher in the sown mixture. Tomato flowers were visited by a small number of wild bees. Their number was not affected by the distance from the field margin, indicating no distraction effect from the sown or natural vegetation flowering plants. Our results suggest that selected flowering plants can improve the field margin habitats for pollinating insects and beneficial arthropods, but more work is needed to elucidate the effect on crop pollination.

Nano-formulation enhances insecticidal activity of natural pyrethrins against Aphis gossypii (Hemiptera: Aphididae) and retains their harmless effect to non-target predators.

The insecticidal activity of a new nano-formulated natural pyrethrin was examined on the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), and the predators Coccinella septempunctata L. (Coleoptera: Coccinellidae) and Macrolophus pygmaeus Rambur (Hemiptera: Miridae), in respect with the nano-scale potential to create more effective and environmentally responsible pesticides. Pyrethrin was nano-formulated in two water-in-oil micro-emulsions based on safe biocompatible materials, i.e., lemon oil terpenes as dispersant, polysorbates as stabilizers, and mixtures of water with glycerol as the dispersed aqueous phase. Laboratory bioassays showed a superior insecticidal effect of the pyrethrin micro-emulsions compared to two commercial suspension concentrates of natural pyrethrins against the aphid. The nano-formulated pyrethrins were harmless, in terms of caused mortality and survival time, to L3 larvae and four-instar nymphs of the predators C. septempunctata and M. pygmaeus, respectively. We expect that these results can contribute to the application of nano-technology in optimization of pesticide formulation, with further opportunities in the development of effective plant protection products compatible with integrated pest management practices.

Sublethal effects of the insecticidal fusion protein ω-ACTX-Hv1a/GNA on the parasitoid Eulophus pennicornis via its host Lacanobia oleracea.

BACKGROUND: The neurotoxin peptide ω-ACTX-Hv1a, fused to the carrier molecule GNA, presents potential for insect control as a biopesticide, being orally toxic to insect pests from different orders. However, thorough evaluation is required to assure its safety towards non-target invertebrates. Effects of this novel biopesticide on the parasitoid Eulophus pennicornis via its host Lacanobia oleracea are presented. RESULTS: Hv1a/GNA did not cause mortality when injected or fed to fifth-stage L. oleracea, but caused up to 39% reduction in mean larval weight (P < 0.05) and increased developmental time when injected. When fed, GNA, but not Hv1a/GNA, caused ∼35% reduction in larval weight, indicating that host quality was not affected by the fusion protein. Although GNA and Hv1a/GNA were internalised by the hosts following ingestion, and thus were available to higher trophic levels, no significant changes in the rate of E. pennicornis parasitism occurred. Number of parasitoid pupae per host, adult emergence and sex ratio were unaffected by GNA- or Hv1a/GNA-treated hosts (P > 0.05). The fusion protein was degraded by parasitoid larvae, rendering it non-toxic. CONCLUSION: Hv1a/GNA has negligible effects on the parasitoid, even under worst-case scenarios. This low toxicity to these insects is of interest in terms of biopesticide specificity and safety to non-target organisms.

Thermal requirements and effect of temperature and prey on the development of the predator Harmonia axyridis.

Thermal requirements (lower temperature threshold and thermal constant) for the development of each developmental stage of the predator Harmonia axyridis (Pallas) were studied on Aphis fabae Scopoli and Dysaphis crataegi (Kaltenbach) under controlled laboratory conditions. The effect of temperature (15, 20, 25, and 30°C) and prey species was examined on pre-imaginal developmental duration and life cycle (pre-oviposition period included) of the predator. Our results suggest comparable thermal requirements for the development of H. axyridis on the particular prey and when compared with other aphid species. The total preimaginal development of H. axyridis, at 15, 20, and 30°C, and its life cycle, at 15 and 30°C, are shorter on D. crataegi than on A. fabae.