Preparation and indoor virulence determination of a temperature-sensitive insecticide against Zeugodacus cucurbitae (Coquillett).

Zeugodacus cucurbitae (Coquillett) is an important fruit and vegetable pest, especially in high-temperature seasons. In our previous research, we developed a temperature-sensitive sustained-release attractant for Z. cucurbitae, that not only can control the release rate of cuelure according to the temperature change, but also shows an excellent trapping effect on Z. cucurbitae. To further enhance the killing effect of the temperature-sensitive attractant on Z. cucurbitae, this study proposed using it in combination with an insecticide to prepare a temperature-sensitive insecticide for Z. cucurbitae. Based on the controlled release technology of pesticides, a temperature-sensitive Z. cucurbitae insecticide was developed by using PNIPAM gel as a temperature-sensitive switch to carry both cuelure and insecticide at the same time. In addition, the lethal effect of different pesticides on Z. cucurbitae were tested by indoor toxicity test, and the best pesticide combination was screened out. The temperature-sensitive insecticide prepared in this study not only had excellent thermal response and controlled release ability, but also enhanced its toxicological effects on Z. cucurbitae because it contained insecticides. Among them, combining thiamethoxam and clothianidin with the temperature-sensitive attractants was the most effective, and their lethality reached more than 97% against Z. cucurbitae. This study is not only of great practical significance for the monitoring and controlling Z. cucurbitae, but also provides theoretical basis and reference value for the combination of temperature-sensitive attractant and insecticide.

The Repellent Capacity against Sitophilus zeamais (Coleoptera: Curculionidae) and In Vitro Inhibition of the Acetylcholinesterase Enzyme of 11 Essential Oils from Six Plants of the Caribbean Region of Colombia.

The repellent capacity against Sitophilus zeamais and the in vitro inhibition on AChE of 11 essential oils, isolated from six plants of the northern region of Colombia, were assessed using a modified tunnel-type device and the Ellman colorimetric method, respectively. The results were as follows: (i) the degree of repellency (DR) of the EOs against S. zeamais was 20-68% (2 h) and 28-74% (4 h); (ii) the IC50 values on AChE were 5-36 µg/mL; likewise, the %inh. on AChE (1 µg/cm3 per EO) did not show any effect in 91% of the EO tested; (iii) six EOs (Bursera graveolens-bark, B. graveolens-leaves, B. simaruba-bark, Peperomia pellucida-leaves, Piper holtonii (1b*)-leaves, and P. reticulatum-leaves) exhibited a DR (53-74%) ≥ C+ (chlorpyrifos-61%), while all EOs were less active (8-60-fold) on AChE compared to chlorpyrifos (IC50 of 0.59 µg/mL). Based on the ANOVA/linear regression and multivariate analysis of data, some differences/similarities could be established, as well as identifying the most active EOs (five: B. simaruba-bark, Pep. Pellucida-leaves, P. holtonii (1b*)-leaves, B. graveolens-bark, and B. graveolens-leaves). Finally, these EOs were constituted by spathulenol (24%)/ß-selinene (18%)/caryophyllene oxide (10%)-B. simaruba; carotol (44%)/dillapiole (21%)-Pep. pellucida; dillapiole (81% confirmed by 1H-/13C-NMR)-P. holtonii; mint furanone derivative (14%)/mint furanone (14%)-B. graveolens-bark; limonene (17%)/carvone (10%)-B. graveolens-leaves.

Chemical Composition and Evaluation of Insecticidal Activity of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum Essential Oils against Stored Products Pests.

The problems of the environment and human health related to the use of synthetic and broad-spectrum insecticides have increasingly motivated scientific research on different alternatives and among these, the use of green systems, such as essential oils, have been explored. Several species of the Apiaceae and Asteraceae families, aromatic herbs rich in secondary bioactive metabolites, are used in the industrial field for pharmaceutical, cosmetic, and food purposes. Different essential oils extracted from some species of these families have shown acute toxicity and attractive and/or repellent effects towards different insects. In our work, we investigated the toxic potential of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum essential oils against four insect species, Sitophilus oryzae, Lasioderma serricorne, Necrobia rufipes, and Rhyzoperta dominica, which are common pests of stored products. The composition of both oils, extracted by hydrodistillation from the aerial parts of the two plants, was evaluated by GC×GC-MS. Calendula incana subsp. maritima essential oil was rich in oxygenated sesquiterpenoids, such as cubebol (35.39%), 4-epi-cubebol (22.99%), and cubenol (12.77%), while the Laserpitium siler subsp. siculum essential oil was composed mainly of monoterpene hydrocarbons, such as ß-phellandrene (42.16%), limonene (23.87%), and ß-terpinene (11.80%). The toxicity Petri dish bioassays indicated that C. maritima oil killed a mean of 65.50% of S. oryzae and 44.00% of R. dominica adults, indicating a higher biocidal activity in comparison with L. siculum oil, while toward the other species, no significant differences in mortality were recorded. Calendula maritima oil could be, then, considered a promising candidate for further tests as an alternative biocide toward S. oryzae and R. dominica. The possibility that the relatively high content of oxygenated sesquiterpenoids in C. maritima essential oil determines its higher biocidal activity is discussed.

Evaluation of the Potential of a Lectin Extracted from Polygonumpersicaria L. as a Biorational Agent against Sitophilusoryzae L.

Rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), is one of the most destructive stored-product pests that is resistant to a wide range of chemical insecticides. In the present study, we investigated whether a lectin extracted from Polygonum persicaria L. (PPA) can be used as a biorational agent to control such insect pests. Along with the lethal digestive assay, the sub-lethal insecticidal activities of PPA, including the effects on digestive, detoxifying, and antioxidant enzyme activities, were evaluated against S. oryzae adults. The effect of feeding a diet containing PPA and carob extract as a food attractant on the mortality of S. oryzae adults was also investigated. Feeding on the diet containing PPA resulted in a significant mortality of S. oryzae adults with a LC50 (Lethal Concentration to kill 50% of insects) of 3.68% (w/w). The activity of digestive enzymes, including α-amylase, α-glucosidase, TAG-lipase, trypsin, chymotrypsin, elastase, and carboxy- and aminopeptidase, were decreased by the sub-lethal concentration of PPA. Detoxifying and antioxidant enzymes, including esterase, superoxide dismutase, catalase, glutathione-S-transferase, ascorbate peroxidase, glucose 6-phosphate dehydrogenase, and malondialdehyde, were activated in adults affected by PPA. These findings indicated that PPA, in addition to causing digestive disorders, leads to oxidative stress in S. oryzae. The presence of carob extract had no effect on the PPA-induced mortality of the insect. According to the results of the present study, PPA has promising insecticidal efficiency against S. oryzae. In addition, the usage of PPA with a food attractant carob extract in bait traps can be recommended as a new biorational formulation in S. oryzae management.

Persistence and ingestion characteristics of phytochemical volatiles as bio-fumigants in Sitophilus oryzae adults.

Fumigant toxicity of phytochemical volatiles has been widely reported against stored product insect pests. Such volatiles are considered as natural fumigants and bio-fumigants in post-harvest food protection research. In the present study, persistence and ingestion of diallyl disulfide, citral, eucalyptol, eugenol and menthol were investigated in Sitophilus oryzae adults in comparison with fumigant toxicity and microstructural impact in elytra. The fumigant toxicity bioassay was performed with increasing concentrations of phytochemical volatiles at 25, 125, 250 and 500 µL/L air against S. oryzae adults in 50 mL glass vials. The phytochemical residues were examined from the treated adults by Gas Chromatography coupled with Flame Ionization Detector (GC-FID) and their pathological impacts on the elytral surface was observed under Scanning Electron Microscopy (SEM). After 72 h of fumigation, diallyl disulfide and eucalyptol were identified as potential fumigants with 5.24 and 8.30 µL/L air LC50 values, respectively. GC-FID analyses showed that diallyl disulfide and eucalyptol molecules persistence (1.29 and 2.60 ppb persistence with 0.94 and 0.90 r2 values respectively at 72 h exposure) on the body surface of weevil was positively correlated with the fumigation exposure and toxicity. Whereas, phytochemical molecules ingestion into the body of weevils was not directly linked with the insect mortalities. The SEM observations indicated that diallyl disulfide and eucalyptol molecules caused severe microstructural impacts on the elytra of weevils compared to other molecules. As a result, the present study suggested that phytochemical fumigants are persisted on the body surface and caused insecticidal toxicities in S. oryzae adults. In addition, it was predicted that persisted molecules might be entered into the body of weevils via cuticular penetration.

Entomotoxic effects of synthesized aluminum oxide nanoparticles against Sitophilus oryzae and their toxicological effects on albino rats.

Recently, nanoparticles are emerging as a potential alternative to synthetic pesticides for protection against stored-product insect pests, such as the rice weevil Sitophilus oryzae; however, the toxic effects of nanoparticles on nontarget organisms are not yet understood. Therefore, we investigated the insecticidal effects of synthesized aluminum oxide nanoparticles (Al2O3-NPs) on S. oryzae, as well as their potential toxicity in albino rats. S. oryzae mortality increased as the period of Al2O3-NP exposure increased; 100% mortality was reached at 8000 mg Al2O3-NPs/kg of wheat grain after 7 days of exposure. After 60 days of exposure, all tested Al2O3-NPs concentrations (1000, 2000, 4000, and 8000 mg/kg grain) significantly reduced the number of S. oryzae offspring in a dose-dependent manner. In albino rats, exposure to the LC90 of Al2O3-NPs in a treated diet caused a significant decrease in total body weight and an increase in liver weight in a subacute toxicity test. Moreover, Al2O3-NP treatment elevated the levels of alanine aminotransferase, aspartate aminotransferase, and creatinine in exposed rats relative to control rats, while the uric acid levels of treated rats decreased. Histopathological analysis also revealed various hepatic and renal lesions in treated rats. In summary, although Al2O3-NPs have insecticidal effects, they also have hazardous toxicological effects on rats. Therefore, if Al2O3-NPs are used in the current powder form to protect stored products, they may cause adverse effects to workers and consumers. Further research will be required to develop new nanoformulations with increased safety and potency before these nanoparticles can be used in stored-product pest control.

Repellent Effects of Selected Organic Leaf Extracts of Tithonia diversifolia (Hemsl.) A. Gray and Vernonia lasiopus (O. Hoffman) against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae).

INTRODUCTION: Sitophilus zeamais infestation is among the major setbacks to sustainable maize farming and availability. It causes an estimated annual loss of 5-10% and 20-30% of the total maize grains loss in the temperate and tropical zones, respectively. Although synthetic pesticides are quick and effective in managing crop pests, their overuse and misuse is discouraged due to their detrimental effects on human and environment. Natural pesticidal products that are extracted from plants are particularly gaining importance as an alternative to synthetic pesticides. They are available, easily biodegraded and have low toxicity to nontarget organisms. Most botanical pesticides act on insects by repelling them away from the crops in the field or in the stores. Therefore, this study aimed to determine repellency potential of organic leaf extracts of Tithonia diversifolia and Vernonia lasiopus on S. zeamais. Materials and methods. The phytochemical profile of T. diversifolia and V. lasiopus was determined using GC-MS. Laboratory-based experiments were carried out using area preference method to assess the efficacy of the extracts against weevils for a test period of 5 h. Six groups of experiments were set up with ten S. zeamais in each test: positive control (Actellic), negative control (solvent only), and four different experimental extract concentrations (25, 50, 75, and 100%). RESULTS: The results indicated that T. diversifolia and V. lasiopus leaf extracts possess potent repellency effect on weevils. All the extracts simply discouraged S. zeamais from the treated areas recording significantly good levels of repellent activities between 26 and 96%. Furthermore, the GC-MS analysis manifested the presence of bioactive compound in the extracts which are associated with the repellency effects. CONCLUSION: The study scientifically confirms the traditional use of the T. diversifolia and V. lasiopus and provides important platform for further study on the extracts as bioresource of botanical repellent.

Synthesis and Insecticidal Evaluation of Chiral Neonicotinoids Analogs: The Laurel Wilt Case.

Xyleborus sp beetles are types of ambrosia beetles invasive to the United States and recently also to Mexico. The beetle can carry a fungus responsible for the Laurel Wilt, a vascular lethal disease that can host over 300 tree species, including redbay and avocado. This problem has a great economic and environmental impact. Indeed, synthetic chemists have recently attempted to develop new neonicotinoids. This is also due to severe drug resistance to "classic" insecticides. In this research, a series of neonicotinoids analogs were synthesized, characterized, and evaluated against Xyleborus sp. Most of the target compounds showed good to excellent insecticidal activity. Generally, the cyclic compounds also showed better activity in comparison with open-chain compounds. Compounds R-13, 23, S-29, and 43 showed a mortality percent of up to 73% after 12 h of exposure. These results highlight the enantioenriched compounds with absolute R configuration. The docking results correlated with experimental data which showed both cation-π interactions in relation to the aromatic ring and hydrogen bonds between the search cavity 3C79 and the novel molecules. The results suggest that these sorts of interactions are responsible for high insecticidal activity.

Intergenerational Transmission of Resistance of Callosobruchus maculatus to Essential Oil Treatment.

Due to the rise of numerous legal restrictions as well as the increasing emergence of resistant populations, the number of available pesticides is decreasing significantly. One of the potential alternatives often described in the literature are essential oils (EOs). However, there is a lack of research addressing the potential emergence of resistance to this group of substances. In this paper, we investigated the multi-generational effects of sublethal concentrations of rosemary oil (Rosmarinus officinalis) on physiological and biochemical parameters of the cowpea weevil (Callosobruchus maculatus) such as egg laying, hatchability, oxygen consumption and acetylcholinesterase activity. Imago, which as larvae were exposed to EO at concentrations equivalent to LC25, showed significantly lower mortality. The results obtained indicate the potential development of resistance in insects exposed to EO in concentrations corresponding to LC25. In addition, in the case of the group treated with an EO concentration corresponding to LC3.12, a stimulation effect of the above-mentioned parameters was observed, which may indicate the occurrence of a hormesis effect. The obtained results may be an important reference for the development of future guidelines and EO-based insecticides.

Bacterial chitinase biochemical properties, immobilization on zinc oxide (ZnO) nanoparticle and its effect on Sitophilus zeamais as a potential insecticide.

It has been planned to minimize the yield and quality impairment of the seed corn, which is strategically important in the world, by pests under storage conditions with a biological product produced with a biotechnological approach. In this context, the present study aimed to control the maize weevil Sitophilus zeamais, known as a warehouse pest, using a nanoformulation. In the study, the chitinase enzyme from Lactobacillus coryniformis was purified first using ammonium sulfate precipitation and then by using the HiTrap Capto DEAE column, and the molecular mass of the purified enzyme was determined to be ~ 33 kDa, and the optimum pH and the values as pH 6.0 and 65-75 °C, respectively. Five different doses of nanoformulation (2, 4, 6, 8 and 10 mg/L) were applied to corn grains by the spraying method with three repetitions so that the insect can ingest the formulation through feeding. The effects of the applications on the death rate and mean time of death of Sitophilus zeamais were determined. According to these findings, it was concluded that the best practice was nanoformulation with 6 mg/L, considering both the mortality rate (100%) and the average death time (2.4 days). Chitinase from L. coryniformis is a promising candidate for corn lice control and management.

Inefficient weapon-the role of plant secondary metabolites in cotton defence against the boll weevil.

MAIN CONCLUSION: Cotton genotypes displayed similar volatile organic compound (VOC) profiles, but major differences in terpenoid aldehyde (TA) content. The differences in VOC production were minor among genotypes, but these differences are crucial for boll weevil attraction. Weevils did not display any preference in feeding behaviour towards cotton genotypes, suggesting physiological adaptation to cope with cotton chemical defence mechanisms. Plant cultivar selection for resistance to herbivore pests is an effective, environmentally safe and inexpensive method to implement in integrated pest management programmes. In this study, we evaluated seven cotton genotypes with respect to the production of volatile organic compounds (VOCs) and non-volatile compounds [terpenoid aldehydes (TAs)], and the attraction and feeding preference of adult boll weevils. Chemical analyses of VOCs from BRS-293, BRS-Rubi, CNPA TB-15, CNPA TB-85, CNPA TB-90, Delta Opal, and Empire Glandless showed that there were few qualitative and quantitative differences across the range of genotypes. In contrast, major differences in TA content were observed, with CNPA TB-15 and CNPA TB-85 producing higher levels of TAs compared to the other genotypes. Our results showed that boll weevil attraction to cotton genotypes varied, suggesting that the ratios and quantities of emitted cotton VOCs are important for host location. However, boll weevil feeding behaviour was neither positively nor negatively influenced by the terpenoid content (non-volatile compounds) of cotton genotypes. The results in this study suggest that boll weevils have adapted physiologically to cope with cotton chemical defence mechanisms.

Composition of Strawberry Floral Volatiles and their Effects on Behavior of Strawberry Blossom Weevil, Anthonomus rubi.

The strawberry blossom weevil (SBW), Anthonomus rubi, is a major pest in strawberry fields throughout Europe. Traps baited with aggregation pheromone are used for pest monitoring. However, a more effective lure is needed. For a number of pests, it has been shown that the attractiveness of a pheromone can be enhanced by host plant volatiles. The goal of this study was to explore floral volatile blends of different strawberry species (Fragaria x ananassa and Fragaria vesca) to identify compounds that might be used to improve the attractiveness of existing lures for SBW. Floral emissions of F. x a. varieties Sonata, Beltran, Korona, and of F. vesca, were collected by both solid-phase microextraction (SPME) and dynamic headspace sampling on Tenax. Analysis by gas chromatography/mass spectrometry showed the floral volatiles of F. x ananassa. and F. vesca were dominated by aromatic compounds and terpenoids, with 4-methoxybenzaldehyde (p-anisaldehyde) and α-muurolene the major compounds produced by the two species, respectively. Multi-dimensional scaling analyses separated the blends of the two species and explained differences between F. vesca genotypes and, to some degree, variation between F. x ananassa varieties In two-choice behavioral tests, SBW preferred odors of flowering strawberry plants to those of non-flowering plants, but weevils did not discriminate between odors from F. x ananassa and F. vesca flowering plants. Adding blends of six synthetic flower volatiles to non-flowering plants of both species increased the preference of SBW for these over the plants alone. When added individually to non-flowering plants, none of the components increased the preference of SBW, indicating a synergistic effect. However, SBW responded to 1,4-dimethoxybenzene, a major component of volatiles from F. viridis, previously found to synergize the attractiveness of the SBW aggregation pheromone in field studies.

Bioactivity of some Apiaceae essential oils and their constituents against Sitophilus zeamais (Coleoptera: Curculionidae).

Sitophilus zeamais is a key pest of stored grains. Its control is made, usually, using synthetic insecticides, despite their negative impacts. Botanical insecticides with fumigant/repellent properties may offer an alternative solution. This work describes the effects of Anethum graveolens, Petroselinum crispum, Foeniculum vulgare and Cuminum cyminum essential oils (EOs) and (S)-carvone, cuminaldehyde, estragole and (+)-fenchone towards adults of S. zeamais. Acute toxicity was assessed by fumigation and topical application. Repellence was evaluated by an area preference bioassay and two-choice test, using maize grains. LC50 determined by fumigation ranged from 51.8 to 535.8 mg L-1 air, with (S)-carvone being the most active. LD50 values for topical applications varied from 23 to 128 µg per adult for (S)-carvone > cuminaldehyde > A. graveolens > C. cyminum > P. crispum. All EOs/standard compounds reduced significantly the percentage of insects attracted to maize grains (65-80%) in the two-choice repellence test, whereas in the area preference bioassay RD50 varied from 1.4 to 45.2 µg cm-2, with cuminaldehyde, (S)-carvone and estragole being strongly repellents. Petroselinum crispum EO and cuminaldehyde affected the nutritional parameters relative growth rate, efficiency conversion index of ingested food and antifeeding effect, displaying antinutritional effects toward S. zeamais. In addition, P. crispum and C. cyminum EOs, as well as cuminaldehyde, showed the highest acetylcholinesterase inhibitory activity in vitro (IC50 = 185, 235 and 214.5 µg mL-1, respectively). EOs/standard compounds exhibited acute toxicity, and some treatments showed antinutritional effects towards S. zeamais. Therefore, the tested plant products might be good candidates to be considered to prevent damages caused by this pest.

Cyantraniliprole susceptibility baseline, resistance survey and control failure likelihood in the coffee berry borer Hypothenemus hampei.

Cyantraniliprole was recently registered for controlling the coffee berry borer Hypothenemus hampei, the main coffee pest in the world. In this study, baseline determination and resistance monitoring to cyantraniliprole were carried out in Brazilian populations of H. hampei. Evaluations were carried out for three years with representative field-collected populations from nine coffee-producing states in Brazil, using artificial diet containing the insecticide. The likelihood of control failure due to cyantraniliprole resistance was also determined. Populations from Campo do Meio, Linhares and Jaú were more susceptible (<2-fold resistance) to cyantraniliprole than populations from Patrocínio and Londrina (17-fold). Nonetheless, the frequency of cyantraniliprole resistance insects was low and not significant throughout the regions survey and the likelihood of control failure was negligible. Therefore, cyantraniliprole remains an important management tool against the coffee berry borer without current problems of control failure. However, enough field variation in susceptibility to cyantraniliprole exists justifying attention and careful management of this insecticide to prevent quick development of insecticide resistance in populations of this insect pest species.

Comparative transcriptome analyses of adzuki bean weevil (Callosobruchus chinensis) response to hypoxia and hypoxia/hypercapnia.

Stored product insects show high adaption to hypoxia and hypercapnia, but the underlying mechanism is still unclear. Herein, a comparative transcriptome on 4th adzuki bean weevil (Callosobruchus chinensis) instar larvae was studied to clarify the response mechanisms to hypoxia (HA) and hypoxia/hypercapnia (HHA) using NextSeq500 RNA-Seq. Transcript profiling showed a significant difference in HA or HHA exposure both quantitatively and qualitatively. Compared with control, 631 and 253 genes were significantly changed in HHA and HA, respectively. Comparing HHA with HA, 1135 differentially expressed genes (DEGs) were identified. The addition of hypercapnia made a complex alteration on the hypoxia response of bean weevil transcriptome, carbohydrate, energy, lipid and amino acid metabolism were the most highly enriched pathways for genes significantly changed. In addition, some biological processes that were not significantly enriched but important were also discussed, such as immune system and signal transduction. Most of the DEGs related to metabolism both in HHA and HA were up-regulated, while the DEGs related to the immune system, stress response or signal transduction were significantly down-regulated or suppressed. This research reveals a comparatively full-scale result in adzuki bean weevil hypoxia and hypoxia/hypercapnia tolerance mechanism at transcription level, which might provide new insights into the genomic research of this species.

Lethality of Sesquiterpenes Reprogramming Red Palm Weevil Detoxification Mechanism for Natural Novel Biopesticide Development.

Natural biopesticide development for invasive populations of red palm weevils is mainly responsible for the destruction of date palms and demands an extensive screening program of plant secondary metabolites. In the current study, the pesticidal potential of sesquiterpenes (C15 H24), an important class of plant secondary metabolites primarily composed of three isoprene units, was evaluated by laboratory toxicity, feeding performance bioassays, and host detoxification gene expression patterns. Dose-mortality response bioassays performed against mid-aged eighth-instar red palm weevil larvae revealed dose-dependent mortality. Only three sesquiterpenes, including Farnesol (LD50 = 6559 ppm) and Farnesyl acetate (LD50 = 7867 ppm), are considered to have significant toxicity, with Picrotoxin (LD50 = 317 ppm) being the most toxic. Furthermore, highly toxic sesquiterpene (Picrotoxin) established in the current study tremendously reduced the feeding performance indices, including the efficacy of conversion of digested food (ECD) (81.74%) and the efficacy of conversion of ingested food (ECI) (73.62%). The least toxic sesquiterpenes, including ß-Caryophyllene, (+)-Cedrol, Nerolidol, (+)-Nootkatone, and Parthenolide, observed in the current study failed to impart significant reductions of ECI and ECD indices. Lethality of the least toxic sesquiterpenes was overcome by greatly inducing gene expressions of Glutathione S transferase (GST) and Cytochrome P450. These encouraging results enabled us to suggest Picrotoxin as a promising biopesticide for the control of red palm weevil infestations.

Complex Interactions among Sheep, Insects, Grass, and Fungi in a Simple New Zealand Grazing System.

Epichloë fungi (Ascomycota) live within aboveground tissues of grasses and can have important implications for natural and managed ecosystems through production of alkaloids. Nonetheless, vertebrate herbivores may possess traits, like oral secretions, that mitigate effects of alkaloids. We tested if sheep saliva mitigates effects of Epichloë alkaloids on a beetle pest of perennial ryegrass (Lolium perenne L.) in a New Zealand pasture setting. Plants with one of several fungal isolates were clipped with scissors, grazed by sheep, or clipped with sheep saliva applied to cut ends of stems. We then assessed feeding damage by Argentine stem weevils on blade segments collected from experimental plants. We found that clipping plants induced synthesis of an alkaloid that reduces feeding by beetles and that sheep saliva mitigates this effect. Unexpectedly, the alkaloid (perloline) that explains variation in beetle feeding is one produced not by the endophyte, but rather by the plant. Yet, these effects depended upon fungal isolate. Such indirect, complex interactions may be much more common in both managed and natural grassland systems than typically thought and could have implications for managing grazing systems.

Toxicological effect of underutilized plant, Cleistanthus collinus leaf extracts against two major stored grain pests, the rice weevil, Sitophilus oryzae and red flour beetle, Tribolium castaneum.

Toxicity and repellency activity of Cleistanthus collinus (Roxb.) (CC) leaf extracts were evaluated against rice weevil, Sitophilus oryzae (L.) and red flour beetle, Tribolium castaneum (Herbst) under laboratory condition. Five concentration(s) (1%, 1.5%, 2%, 2.5% and 4%) with two controls (acetone and water) treatments along with deltamethrin were used for direct and contact residual toxicity. The insect that survived after CC exposure were transferred to an untreated feeding substrate and the population buildup of subsequent two generation were recorded after 30 (F1) and 60 days (F2). In the contact residual toxicity, highest CC concentration (4%) produced 75% mortality in S. oryzae and 62.5% mortality in T. castaneum during 7 days of exposure, whereas in direct toxicity the mortality were 81% and 58% respectively, for S. oryzae and T. castaneum. The long term effect of CC was apparent in both the insect species, where F2 populations were significantly decreased in the CC treatments. CC treatment at 4% produced similar adult mortality in comparison to deltamethrin at 1%. In addition, repellent activity of CC extracts was observed against both S. oryzae and T. castaneum. This is the first step towards assessing the scientific basis for the understanding the effectiveness of CC extracts against stored grain pests and it could be a viable eco-friendly option for stored grain insect pest management.

Terpenoid constituents of cinnamon and clove essential oils cause toxic effects and behavior repellency response on granary weevil, Sitophilus granarius.

This study evaluated toxic effects, repellency and respiration rate caused by terpenoid constituents of cinnamon and clove essential oils and against Sitophilus granarius L. (Coleoptera: Curculionidae). The lethal concentrations (LC50 and LC90), repellent effect, and behavior repellency response on adults of S. granarius after exposure to six concentrations of each essential oil and terpenoids were evaluated. The chemical composition of the cinnamon oil was also determined and primary compounds were eugenol (10.5%), trans-3-caren-2-ol (10.2%), benzyl benzoate (9.99%), caryophyllene (9.34%), eugenyl acetate (7.71%), α-phellandrene (7.41%), and α-pinene (7.14%). In clove essential oil, the primary compounds were eugenol (27.1%), caryophyllene (24.5%), caryophyllene oxide (18.3%), 2-propenoic acid (12.2%), α-humulene (10.8%), γ-cadinene (5.01%), and humulene oxide (4.84%). Cinnamon and clove essential oil was toxic to S. granarius. In toxic terpenoids compounds, eugenol has stronger contact toxicity in S. granarius than caryophyllene oxide, followed by α-pinene, α-humulene, and α-phellandrene. Insects reduced their respiratory rates after being exposed to essential oil terpenoids and avoided or reduced their mobility on terpenoid-treated surfaces. Cinnamon and clove essential oil, and their terpenoid constituents were toxic and repellent to adult S. granarius and, therefore, have the potential to prevent or retard the development of insecticide resistance.

Volatile Profiling, Insecticidal, Antibacterial and Antiproliferative Properties of the Essential Oils of Bursera glabrifolia Leaves.

The present article describes the chemical composition and biological activities of the essential oils of B. glabrifolia leaves obtained in four consecutive years (2015-2018). The essential oils contained α-terpineol (17.9-29.7 %), α-terpinene (12.6-17.4 %), limonene (14.9-26.8 %) and ß-pinene (2.1-16.7 %) as the most abundant volatiles. The essential oils and these volatiles showed a significant adulticide activity (p<0.01; LC50 <100 µg mL-1 ) on the maize weevil (Sitophilus zeamais) with a 100 % mortality rate within a period of 5 h. Also, the essential oils showed a strong antibacterial activity on Enterococcus faecalis ATCC 29212 (MIC, 132.7-173.6 µg mL-1 ) and Helicobacter pylori ATCC 43504 (MIC, 74.8-199.2 µg mL-1 ). The assessment of the main volatiles revealed α-terpineol as the principal antibacterial agent (MIC, 78.6-149.7 µg mL-1 ). Similarly, the essential oils exhibited a substantial in vitro antiproliferative activity on the human prostate cancer cell lines PC-3 (LC50 , 15.2-19.4 µg mL-1 ), the human ovarian carcinoma cell lines OVCAR-3 (LC50 , 27.3-53.7 µg mL-1 ) and the myelogenous leukemia cell lines K-562 (LC50 , 32.4-75.9 µg mL-1 ). α-Terpineol (LC50 , 32.4-75.9 µg mL-1 ) exhibited the strongest antiproliferative effect on these cancer cell lines (LC50 , 22.4-48.1 µg mL-1 ).