The Herbicidal Potential of Different Pelargonic Acid Products and Essential Oils against Several Important Weed Species

There is growing consideration among farmers and researchers regarding the development of natural herbicides providing sufficient levels of weed control. The aim of the present study was to compare the efficacy of four different pelargonic acid products, three essential oils and two natural products’ mixtures against L. rigidum Gaud., A. sterilis L. and G. aparine L. Regarding grass weeds, it was noticed at 7 days after treatment that PA3 treatment (pelargonic acid 3.102% w/v + maleic hydrazide 0.459% w/v) was the least efficient treatment against L. rigidum and A. sterilis. The mixture of lemongrass oil and pelargonic acid resulted in 77% lower dry weight for L. rigidum in comparison to the control. Biomass reduction reached the level of 90% as compared to the control in the case of manuka oil and the efficacy of manuka oil and pelargonic acid mixture was similar. For sterile oat, weed biomass was recorded between 31% and 33% of the control for lemongrass oil, pine oil, PA1 (pelargonic acid 18.67% + maleic hydrazide 3%) and PA4 (pelargonic acid 18.67%) treatments. In addition, the mixture of manuka oil and pelargonic acid reduced weed biomass by 96% as compared to the control. Regarding the broadleaf species G. aparine, PA4 and PA1 treatments provided a 96–97% dry weight reduction compared to the corresponding value recorded for the untreated plants. PA2 (pelargonic acid 50% w/v) treatment and the mixture of manuka oil and pelargonic acid completely eliminated cleaver plants. The observations made for weed dry weight on the species level were similar to those made regarding plant height values recorded for each species. Further research is needed to study more natural substances and optimize the use of natural herbicides as well as natural herbicides’ mixtures in weed management strategies under different soil and climatic conditions.

Mānuka Oil—A Review of Antimicrobial and Other Medicinal Properties

Mānuka oil is an essential oil derived from Leptospermum scoparium, a plant that has been used by the indigenous populations of New Zealand and Australia for centuries. Both the extracted oil and its individual components have been associated with various medicinal properties. Given the rise in resistance to conventional antibiotics, natural products have been targeted for the development of antimicrobials with novel mechanism of action. This review aimed to collate available evidence on the antimicrobial, anti-parasitic and anti-inflammatory activities of mānuka oil and its components. A comprehensive literature search of was conducted using PubMed and Embase (via Scopus) targeting articles from database inception until June 2020. Chemical structures and IUPAC names were sourced from PubChem. Unpublished information from grey literature databases, Google search, targeted websites and Google Patents were also included. The present review found extensive in vitro data supporting the antimicrobial effects of mānuka oil warrants further clinical studies to establish its therapeutic potential. Clinical evidence on its efficacy, safety and dosing guidelines are necessary for its implementation for medical purposes. Further work on regulation, standardization and characterization of the medicinal properties of mānuka oil is required for establishing consistent efficacy of the product.

Improving the field efficacy of manuka oil using tank-mixes with surfactants and commercial organic herbicides

Manuka oil was applied in combination with surfactants and other organic herbicides for a total of 10 different treatments. Three surfactants (Nu Film P, Agral 90, and yucca extract) and two essential oil based organic herbicides (clove–cinnamon oil and citrus oil) were tank-mixed with manuka oil. Herbicide treatments were analyzed against two checks (weedy and weed-free) in eight unique scenarios to determine what tank-mix options enhanced the preemergence (PRE) and postemergence (POST) efficacy of manuka oil. The eight unique scenarios included two locations (Simcoe and Ridgetown, ON), two crops (sweet corn and tomatoes), and two planting dates (early and late). Crop yield and visual weed efficacy data indicated that manuka oil had very weak PRE herbicidal properties in field scenarios. Manuka oil based treatments caused minimal crop injury on recently transplanted tomatoes and newly emerging sweet corn seedlings. Manuka oil was able to provide good weed control when applied POST either alone or in tank-mixes. The efficacy of manuka oil increased when manuka oil was used as a tank-mix partner compared with manuka oil applied alone.

Species assemblage of buprestid beetles in four hardwood cover types in Michigan

Information on species assemblages of metallic wood-boring beetles (Coleoptera: Buprestidae) in forested habitats in North America is relatively scarce, likely reflecting the difficulty of effectively trapping and accurately identifying species. We identified buprestid species captured on four baited traps placed in each of 12 sites representing four common forest cover types in five Michigan counties. Overstory vegetation was dominated by ash (Fraxinus spp.), maple (Acer spp.), oak (Quercus spp.), or poplar (Populus spp.) trees (three sites per cover type). A total of 1656 buprestids representing 28 species were captured on sticky purple prism traps baited with either cis-3-hexenol plus Manuka oil or 3R-hydroxyhexane-2-one plus ethanol from May to August 2014. Buprestid species richness ranged from 6 to 13 species per site. PERMANOVA results showed that buprestid species composition differed among forest cover types (P < 0.005). The invasive Agrilus sulcicollis Lacordaire and the native Chrysobothris femorata Olivier species group were significant indicators of oak sites, while Agrilus obsoletoguttatus Gory was a significant indicator of maple sites. Nonmetric multidimensional scaling showed that abundance of captured buprestids was influenced by availability of fresh snags and coarse woody debris. Our results indicate that trapping can provide an efficient means to assess assemblages of phloem- or wood-boring buprestids.

Further evidence that monochamol is attractive to Monochamus (Coleoptera: Cerambycidae) species, with attraction synergised by host plant volatiles and bark beetle (Coleoptera: Curculionidae) pheromones

Monochamol (2-undecyloxy-1-ethanol) is a male-produced aggregation pheromone for several Monochamus Dejean (Coleoptera: Cerambycidae) species. We conducted trapping experiments in Canada, Poland, and China to test whether monochamol was attractive to additional Monochamus species and if attraction was synergised by plant volatiles and bark beetle (Coleoptera: Curculionidae) pheromones. We provide the first evidence of attraction for M. urussovii (Fischer) and M. saltuarius (Gebler) to monochamol or monochamol+kairomones. The highest numbers of M. urussovii were captured in traps baited with monochamol+plant volatiles (Manuka oil, ethanol and (95/5±) α−pinene). Captures of M. saltuarius were highest in traps baited with monochamol, with the addition of cubeb oil tending to reduce captures. The highest numbers of M. scutellatus (Say) were captured in traps baited with monochamol+kairomones. A similar pattern in trap captures was found for M. notatus (Drury), M. marmorator Kirby, M. carolinensis (Olivier), and M. mutator LeConte. Detection rates, that is, proportion of traps capturing at least one specimen, was highest for traps baited with monochamol plus kairomones, particularly for less-common species. These results support the emerging hypothesis that pheromone compounds can attract related cerambycid species with cumulative evidence for attraction to monochamol for 12 species of Monochamus worldwide.

Topical Administration of Manuka Oil Prevents UV-B Irradiation-Induced Cutaneous Photoaging in Mice

Manuka tree is indigenous to New Zealand, and its essential oil has been used as a traditional medicine to treat wounds, fever, and pain. Although there is a growing interest in the use of manuka oil for antiaging skin care products, little is known about its bioactivity. Solar ultraviolet (UV) radiation is the primary environmental factor causing skin damage and consequently premature aging. Therefore, we evaluated manuka oil for its effects against photoaging in UV-B-irradiated hairless mice. Topical application of manuka oil suppressed the UV-B-induced increase in skin thickness and wrinkle grading in a dose-dependent manner. Application of 10% manuka oil reduced the average length, depth, and % area of wrinkles significantly, and this was correlated with inhibition of loss of collagen fiber content and epidermal hyperplasia. Furthermore, we observed that manuka oil could suppress UV-B-induced skin inflammation by inhibiting the production of inflammatory cytokines. Taken together, this study provides evidence that manuka oil indeed possesses antiphotoaging activity, and this is associated with its inhibitory activity against skin inflammation induced by UV irradiation.