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Feeding of sucking insects, such as the rice brown planthopper (Nilaparvata lugens; BPH), causes only limited mechanical damage on plants that is otherwise essential for injury-triggered defense responses against herbivores. In pursuit of complementary BPH elicitors perceived by plants, we examined the potential effects of BPH honeydew secretions on the BPH monocot host, rice (Oryza sativa). We found that BPH honeydew strongly elicits direct and putative indirect defenses in rice, namely accumulation of phytoalexins in the leaves, and release of volatile organic compounds from the leaves that serve to attract natural enemies of herbivores, respectively. We then examined the elicitor active components in the honeydew and found that bacteria in the secretions are responsible for the activation of plant defense. Corroborating the importance of honeydew-associated microbiota for induced plant resistance, BPHs partially devoid of their microbiota via prolonged antibiotics ingestion induced significantly less defense in rice relative to antibiotic-free insects applied to similar groups of plants. Our data suggest that rice plants may additionally perceive herbivores via their honeydew-associated microbes, allowing them to discriminate between incompatible herbivores—that do not produce honeydew—and those that are compatible and therefore dangerous.

Although blossom and honeydew honeys are produced from different nectar sources, it is very difficult to distinguish them. In this study, physicochemical and biochemical properties were compared to distinguish honeydew and blossom honeys obtained from different botanical sources. The honeys of pine (Pinus spp.) and oak (Quercus, spp.) were used as honeydew honey, and chestnut (Castania sativa L.) and highland honey were used as blossom honey. Turbidity, specific optical rotation (SOR) [α]20, electrical conductivity (EC), CIEL* a*b color parameters, and moisture and pH were assessed as physical parameters. Proline, invertase activity, sugar composition, total phenolic and flavonoid contents, and antioxidant capacity were used as biochemical properties. It was determined that SOR values were the most important parameters in distinguishing honeydew and blossom honeys. Turbidity stands out as a crucial factor in differentiating between pine and oak honeys. Except for chestnut honey, electrical conductivity, CIE color Lab values, and sugar profiles were identified as additional distinguishing factors among the tested honeys.

Phlebopus portentosus and mealy bugs form a fungus-insect gall on the roots of host plants. The fungus and mealy bugs benefit mutually through the gall, which is the key link in the nutritional mechanism of P. portentosus. The cavity of the fungus-insect gall provides an ideal shelter for mealy bugs survival and reproduction, but how does P. portentosus benefit from this symbiotic relationship? Anatomical examination of fungus-insect galls revealed that one or more mealy bugs of different generations were living inside the galls. The mealy bug's mouthpart could penetrate through the mycelium layer of the inside of the gall and suck plant juice from the host plant root. Mealy bugs excreted honeydew inside or outside the galls. The results of both honeydew agar medium and quartz tests showed that the honeydew can attract and promote the mycelial growth of P. portentosus. A test of the relationship between the honeydew and the formation of the fungus-insect gall showed that honeydew promoted gall formation. All experimental results in this study show that the honeydew secreted by mealy bugs can attract and promote the mycelial growth of P. portentosus, forming a fungus-insect gall, because mealy bugs' honeydew is rich in amino acids and sugars.

(E)-β-Farnesene (EβF) is the predominant constituent of the alarm pheromone of most aphid pest species. Moreover, natural enemies of aphids use EβF to locate their aphid prey. Some plant species emit EβF, potentially as a defense against aphids, but field demonstrations are lacking. Here, we present field and laboratory studies of flower defense showing that ladybird beetles are predominantly attracted to young stage-2 pyrethrum flowers that emitted the highest and purest levels of EβF. By contrast, aphids were repelled by EβF emitted by S2 pyrethrum flowers. Although peach aphids can adapt to pyrethrum plants in the laboratory, aphids were not recorded in the field. Pyrethrum’s (E)-β-farnesene synthase (EβFS) gene is strongly expressed in inner cortex tissue surrounding the vascular system of the aphid-preferred flower receptacle and peduncle, leading to elongated cells filled with EβF. Aphids that probe these tissues during settlement encounter and ingest plant EβF, as evidenced by the release in honeydew. These EβF concentrations in honeydew induce aphid alarm responses, suggesting an extra layer of this defense. Collectively, our data elucidate a defensive mimicry in pyrethrum flowers: the developmentally regulated and tissue-specific EβF accumulation and emission both prevents attack by aphids and recruits aphid predators as bodyguards.

Worldwide, the most ecologically damaging invasive ants are associated with introduced honeydew‐producing insects, yet the mechanisms by which this mutualism may support invasive ant populations and drive impacts remain unclear. On Christmas Island, the invasive yellow crazy ant (Anoplolepis gracilipes; YCA), found in association with introduced honeydew‐producing scale insects, can reach extraordinary densities, triggering an ecological meltdown. In this study, we utilized stable isotope analysis to determine resource use of YCAs in naturally occurring low‐ and high‐density populations, and we conducted laboratory experiments mimicking availability of honeydew to measure effects of carbohydrate subsidies on colony growth and worker behavior. High‐density YCA populations in nature incorporated a larger proportion of plant‐based resources in their diet than low‐density populations, and laboratory colonies with access to greater sugar resources had larger colony sizes, higher reproduction rates and worker survival, and higher per capita activity levels and showed higher aggression and potency toward opponents. These results support the positive feedback mechanism between honeydew‐producing insects and YCAs that underlies the ecological meltdown on Christmas Island, and add to the growing body of literature illustrating the importance of mutualistic interactions in the success of invasive species.

Honey is a complex mixture of carbohydrates, in which the monosaccharides glucose and fructose are the most abundant compounds. Currently, more than 20 oligosaccharides have been identified in different varieties of honey normally at quite low concentration. A method was developed and validated using high-performance anion-exchange chromatography coupled to a mass spectrometry detector to investigate the composition of carbohydrates in honey samples. The method was tested for linearity range, trueness, instrumental and method detection and quantification limits, repeatability, and reproducibility. It was applied to determine seven monosaccharides, eight disaccharides, four trisaccharides, and one tetrasaccharide in various honey samples. The present work describes the composition of sugars in unifloral, multifloral, and some honeydew honey, which were produced and collected by beekeepers in the Trentino Alto-Adige region. Statistical techniques have been used to establish a relationship based on levels of carbohydrates among different Italian honey. The results emphasize that mono- and oligosaccharide profiles can be useful to discriminate different honeys according to their floral characteristics and inter-annual variability.

Originating from New Zealand manuka honey distinguishes itself from other honeys. The purpose of this study was to compare the antioxidant and antimicrobial properties of manuka honey and selected Polish honeys. Antioxidant capacity, total polyphenol and total flavonoid content were determined. Furthermore, the antimicrobial activity and the Minimum Inhibitory Concentration (MIC) were evaluated. Obtained results demonstrated that manuka honeys possessed relatively high antioxidant capacity compared to the other, Polish honeys. It was only honeydew honey that achieved comparable antioxidant properties to manuka honeys. The findings were supported by the results of microbial assays. Manuka MGO-250 and MGO-400, alongside honeydew honey, showed a stronger antimicrobial effect against Gram(+) than against Gram(−) bacteria. Moreover, the MIC-values, expressed as an inhibin number, proved the high antibiotic activity of manuka honey against the strains of Staphylococcus aureus and Enterococcus faecalis. Research concerning the influence of manuka honey on human health should be continued.

The aim of the present study was to compare the antioxidant, antibacterial and antiviral activities of Podkarpackie coniferous honeydew honey and Manuka honey. The quality of tested honey samples (honeydew-12 and Manuka-4) regarding honey standard was evaluated as well as additional indicators (methylglyoxal, total phenolics and HPTLC phenolic profile, antioxidant potential, glucose oxidase activity, and hydrogen peroxide) were compared. Antibacterial potential was analyzed against Gram-positive ( S. aureus and B. cereus ) and Gram-negative ( E. coli and S. enterica ) bacteria. Antiviral activity against different RNA (phi6, MS2) and DNA (T7, phiX174) bacteriophages considered as “viral surrogates” was determined. Based on the determined physicochemical parameters the good quality of tested honeys was confirmed, excluding two samples. The content of polyphenolic compounds in honeydew honey ranged from 583.87 to 1102.42 mg of gallic acid/kg and was strongly correlated with the antioxidant properties. Moreover, for samples with the strongest activity these parameters were comparable to Manuka honey. However, the obtained HPTLC polyphenolic profiles were completely different for honeydew than for Manuka honey which exhibited additional bands (Rf = 0.74 and 0.52). Honeydew honeys were characterized by a strong antiviral and antibacterial properties most of all against Gram-positive bacteria. The MICs (minimal inhibitory concentrations) for S. aureus and B. cereus ranged 15–35% and 8–15% for honeydew and Manuka honeys, respectively. The strongest antiviral properties of honeydew honey were demonstrated mainly against RNA bacteriophages (phi6, MS2) which was even higher than for Manuka honey, especially against MS2 virus. The obtained results suggest that Podkarpackie honeydew honey with the controlled glucose oxidase activity may be a natural substance used to combat viral and bacterial diseases.

This study was conducted to determine the characteristic properties of Turkish pine honey, which is an important honeydew honey. The geographical classification of the honey was determined by applying carbon isotope, melissopalynological, and physicochemical analyses to 373 samples collected from 47 regions between 2015 and 2017 under controlled conditions. δ13C protein-δ13Choney, C4%, electrical conductivity, moisture, ash, free acidity, color CIEL* a*b attributes, optical rotation [α]20, proline, diastases activities, and sugars (fructose, glucose, sucrose, and maltose) were used as physicochemical properties. Number of honeydew elements /number of total pollen (NHE/NTP) ratios were studied at melissopalynological analyses. The results showed that all samples exhibited honeydew properties, and that all physicochemical parameters met the criteria set by regulatory standards for honeydew. However, C4% sugar and δ13C protein-δ13C honey values did not meet the regulatory criteria and exhibited quite wide standard deviations.

Honeydew honey (HH) is a distinctive type of honey known for its dark colour, high mineral and polyphenol content, and pronounced biological activity. This study continues previous research on beech and chestnut honeydew honeys by presenting a comprehensive analysis of linden honeydew honey (LHH) from Bosnia and Herzegovina—a variety that, until now, has not been characterised in detail. Physicochemical parameters confirmed its classification as HH, with high electrical conductivity (1.21 mS/cm) and low moisture (15.1%). GC-MS analysis revealed a unique volatile profile dominated by α-terpinolene (17.4%), distinguishing LHH from other HH types. The sample exhibited high total phenolic content (816.38 mg GAE/kg) and moderate antioxidant capacity (1.11 mmol TE/kg). Antimicrobial testing demonstrated strong activity against Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (MRSA), with lower efficacy against Gram-negative bacteria. No cytotoxic effects were observed in HaCaT keratinocytes at concentrations up to 60 mg/mL, and wound healing assays showed improved scratch closure reaching approximately 30% after 24 h and 41% after 48 h compared to the control. These results indicate that LHH possesses promising bioactive properties and potential for dermatological application. Further studies with broader sample sets are needed to explore variability and confirm the therapeutic relevance of LHH in comparison to other honeydew types.