Terpenoid-Induced Feeding Deterrence and Antennal Response of Honey Bees

Multiple interacting stressors negatively affect the survival and productivity of managed honey bee colonies. Pesticides remain a primary concern for beekeepers, as even sublethal exposures can reduce bee immunocompetence, impair navigation, and reduce social communication. Pollinator protection focuses on pesticide application guidelines; however, a more active protection strategy is needed. One possible approach is the use of feeding deterrents that can be delivered as an additive during pesticide application. The goal of this study was to validate a laboratory assay designed to rapidly screen compounds for behavioral changes related to feeding or feeding deterrence. The results of this investigation demonstrated that the synthetic Nasonov pheromone and its terpenoid constituents citral, nerol, and geraniol could alter feeding behavior in a laboratory assay. Additionally, electroantennogram assays revealed that these terpenoids elicited some response in the antennae; however, only a synthetic Nasonov pheromone, citral, and geraniol elicited responses that differed significantly from control and vehicle detections

Identification of compounds from Etonia rosemary \u3ci\u3e(Conradina etonia)\u3c/i\u3e

Mosquitoes transmit pathogens that result in diseases harmful to human, livestock, and wildlife hosts. Numerous measures can be used to reduce insect-borne disease risk to humans, and one approach is the use of topical repellents to prevent host-seeking arthropods from taking a blood meal. A current emphasis in the development of new repellents is that they be safe. Therefore, natural products sources are increasingly being explored. Compounds from plants of the mint family (Lamiaceae) have been demonstrated to be insect repellents. This study examines compounds from Etonia rosemary (Conradina etonia) to identify compounds for examination as insect repellents. Samples of Etonia rosemary were passively extracted with hexane, dichloromethane, and methanol and analyzed by GC/MS. This extraction method was chosen to eliminate thermal degradation of plant components that can occur during the distillation procedure. Additional headspace volatile compounds from this plant were identified using microscale purge-and-trap GC/MS. A variety of terpenes, terpenic alcohols, ketones, and aldehydes were identified in the extracts with terpenes and short-chained aldehydes detected in greatest abundance

Effect of Vacuum on the Performance of the Flame Ionization Detector Used for Vacuum-Outlet Gas Chromatography

Vacuum-outlet operation of short fused-silica open tubular columns for gas chromatography provides benefits to analysis speed by increasing the optimum velocity while minimizing the loss in resolution. Vacuum-outlet operation of a column with a gas chromatographic detector necessitates that the detector also be under vacuum. Simple modifications were made to a gas chromatograph-flame ionization detector (GC-FID) for vacuum-inlet and vacuum-outlet operation. The vacuum-inlet system was operated in the splitless mode to allow for efficient sample loading prior to operation at reduced pressures. The goal of FID operation at 100 torr or less was achieved by using oxygen in place of air and optimizing the gas flows under vacuum to maintain a stable flame at pressures as low as 46 torr. An outlet pressure of 85 torr with optimized gas flows allowed for routine operation of the FID without solvent flame-out. It was discovered that the sensitivity is enhanced compared to atmospheric operation over a range of outlet pressures from approximately 200 to 400 torr; however, operation of the FID at the lowest possible pressures decreases the analytical sensitivity due to both the outlet pressure and the absence of helium makeup gas

Efficacy Of Three Attractant Blends Tested In Combination With Carbon Dioxide Against Natural Populations Of Mosquitoes And Biting Flies At The Lower Suwannee Wildlife Refuge

Synthetic blends of chemicals identified previously from human skin emanations were evaluated against mosquito and biting fly populations at the Lower Suwannee Wildlife Refuge near Cedar Key, FL. Mosquito MagnetTM-Experimental traps were baited with the Red (400 ml acetone:10 ml 1-hexen- 3-ol:10 ml 1-octen-3-ol), Blue (400 ml acetone:1 g/liter lactic acid:20 ml glycolic acid), or Green blend (400 ml acetone:1.5 g/liter lactic acid:20 ml dimethyl disulfide) plus CO2 or with CO2 alone (control). A relative index of efficacy was determined by dividing each mean blend trap catch by the mean control trap catch. Five mosquitoes (Aedes infirmatus, Ae. taeniorhynchus, Ae. triseriatus, Anopheles crucians, and Culex nigripalpus), 2 ceratopogonid (Culicoides floridensis and C. furens), and 1 tabanid (Diachlorus ferrugatus) and phlebotomine (Lutzomyia shannoni) species were trapped. The Red blend + CO2 treatment significantly increased collections of Ae. taeniorhynchus (3.4×), An. crucians (2.8×), total mosquitoes (2.7×), C. furens (17.6×), and L. shannoni (10.8×) compared with control traps. Traps baited with either the Blue or Green blends generally captured fewer insects than traps baited with the other 2 treatments. However, traps baited with the Green blend caught 7× as many C. furens as the control traps. Responses clearly varied according to species; therefore, ‘‘one size does not fit all’’ when it comes to attractant blends

Elution Patterns From Capillary GC For Methyl-Branched Alkanes

A common and confusing problem in analyses of insect hydrocarbons is in making sense of complicated gas chromatograms and interpreting mass spectra since branched chain compounds differing by one or two carbons in backbone or chain length may elute from the column at nearly the same time. To address this confusing situation, relative gas chromatography (GC) retention times are presented for typical mono-, di-, tri-, and tetramethylalkanes comprising most of the commonly appearing series of homologous methyl-branched alkanes up to 53 carbons that are found in insect cuticular hydrocarbons. Typical insect-derived methylalkanes with backbones of 33 carbons were characterized by Kovats indices (KI); monomethyl alkanes elute between KI 3328 and 3374, dimethylalkanes elute between KI 3340 and 3410, trimethylalkanes elute between KI 3378 and 3437, and tetramethylalkanes elute between KI 3409 and 3459, depending upon the positions of substituents. A protocol is described for identification of methyl-branched hydrocarbons eluted from nonpolar polysiloxane DB-1 capillary GC columns. In this protocol, retention indices (KI values) are assigned to peaks, then the patterns in GC peaks that probably contain homologs are marked to assist subsequent GC-mass spectrometric (GC-MS) interpretation. Use of the KI allows assignment of likely structures and the elimination of others, with demonstrative consistency, as there are no known exceptions. Interpretation of electron ionization mass spectra can then proceed within narrowed structural possibilities without the necessity of chemical ionization GC-MS analysis. Also included are specific examples of insect hydrocarbons that were assembled from 30 years of the literature, and these are intended to help with confirmation of confusing or contradictory structures

Distinctive Hydrocarbons of the Black Dump Fly, \u3ci\u3eHydrotaea aenescens\u3c/i\u3e (Diptera: Muscidae)

Hydrotaea aenescens (Wiedemann), the black dump fly, is a potential biological control agent originally from the western hemisphere, now found in many parts of the Palearctic region except for the United Kingdom, where it cannot be imported for any reason. A complication of classical biological control is the problem of strain identification, as one must be able to somehow mark or follow a particular strain that has been introduced into the field or is contemplated for release. Gas chromatographic analysis of the surface hydrocarbons of pooled and individual dump fly adults resulted in reproducible hydrocarbon patterns that differentiated widely distributed strains of H. aenescens and showed similarities between strains that were related. Sexual dimorphism was observed in the surface hydrocarbons. Conspecific similarities included identities of the hydrocarbons found in colony material collected worldwide, with differences being found in the quantities of compounds present

Distinctive Hydrocarbons of the Black Dump Fly, \u3ci\u3eHydrotaea aenescens\u3c/i\u3e (Diptera: Muscidae)

Hydrotaea aenescens (Wiedemann), the black dump fly, is a potential biological control agent originally from the western hemisphere, now found in many parts of the Palearctic region except for the United Kingdom, where it cannot be imported for any reason. A complication of classical biological control is the problem of strain identification, as one must be able to somehow mark or follow a particular strain that has been introduced into the field or is contemplated for release. Gas chromatographic analysis of the surface hydrocarbons of pooled and individual dump fly adults resulted in reproducible hydrocarbon patterns that differentiated widely distributed strains of H. aenescens and showed similarities between strains that were related. Sexual dimorphism was observed in the surface hydrocarbons. Conspecific similarities included identities of the hydrocarbons found in colony material collected worldwide, with differences being found in the quantities of compounds present

Terpenoid-Induced Feeding Deterrence and Antennal Response of Honey Bees

Multiple interacting stressors negatively affect the survival and productivity of managed honey bee colonies. Pesticides remain a primary concern for beekeepers, as even sublethal exposures can reduce bee immunocompetence, impair navigation, and reduce social communication. Pollinator protection focuses on pesticide application guidelines; however, a more active protection strategy is needed. One possible approach is the use of feeding deterrents that can be delivered as an additive during pesticide application. The goal of this study was to validate a laboratory assay designed to rapidly screen compounds for behavioral changes related to feeding or feeding deterrence. The results of this investigation demonstrated that the synthetic Nasonov pheromone and its terpenoid constituents citral, nerol, and geraniol could alter feeding behavior in a laboratory assay. Additionally, electroantennogram assays revealed that these terpenoids elicited some response in the antennae; however, only a synthetic Nasonov pheromone, citral, and geraniol elicited responses that differed significantly from control and vehicle detections

Departments of Defense and Agriculture team up to develop new insecticides for mosquito control

Mosquito-borne pathogens are among the most important sources of human disease that cause morbidity and mortality worldwide. They include the viruses responsible for deadly outbreaks of yellow fever, Rift Valley fever, eastern equine encephalitis, Japanese encephalitis and dengue, and an assortment of other serious illnesses caused by the etiological agents of West Nile fever, St Louis encephalitis, Murray Valley encephalitis, Venezuelan equine encephalitis and chikungunya disease. Dengue viruses, of which there are 4 serotypes, cause an estimated 50-100 million new illnesses each year (and 25,000 deaths) while the latest chikungunya epidemic has lasted longer, affected more people, and occurred over a wider geographic area than any previous outbreak of the disease. Yellow fever outbreaks continue to occur sporadically in South America and Africa when either vaccination or vector control are inadequate. These outbreaks have been controlled by creating barrier zones of vaccinated people and by increasing the intensity of vector control. The threat of devastating outbreaks of yellow fever remains, as illustrated by continuing quarantine and vaccination requirements for international travel. The most devastating of all mosquito-borne diseases is malaria, which kills an estimated 1 million people annually, while infecting another 500 million. Although public health efforts have been able to reduce or eliminate vector-borne pathogens in many situations, some parts of the world have actually suffered increases during the past 30 years. A number of agencies have responded to this problem with much increased levels of attention: World Health Organization, Bill and Melinda Gates Foundation, President’s Malaria Initiative, Institute Pasteur, US Centers for Disease Control and Prevention, and US National Institutes of Health. However, morbidity and mortality due to mosquito-borne diseases is increasing. Today, mosquito wars are being fought around the globe and on many fronts. Insecticide-treated bed nets are mass-produced and distributed to the hardesthit malarious regions in Africa, India and southern Asia. Vaccines have been developed to protect humans and domestic animals against Yellow fever, Japanese encephalitis, Rift Valley fever and eastern equine encephalitis, with intensive ongoing research targeting dengue, West Nile virus, and malaria vaccine development. New skin and clothing repellents for personal protection against all biting insects are being developed, and insecticide and related application technology development is in full swing. Of these, the key component for protecting humans from mosquito- borne illness is the use of effective insecticides that quickly kill millions of mosquitoes before they can pass their pathogens to sicken or kill humans. Mosquito adulticides and larvicides are a key component of our assault, along with indoor residual spraying and insecticide-treated bed nets. Unfortunately, mosquitoes are fighting back somewhat successfully by developing resistance to currently used mosquito adulticides. To date at least 100 species of pathogen-carrying mosquitoes have overcome the effects of today’s limited arsenal of adulticides. We now have only 2 chemical classes of adulticides available for adult mosquito control: organophosphates (OPs) and pyrethroids. Malathion is one of our oldest organophosphate adulticides and the workhorse of this class. It was developed in the early 1950s for agricultural pest control and has been used extensively around the world as a mosquito adulticide since 1953. It is a cholinesterase inhibitor that impairs nerve cell transmission. Resistant mosquitoes have at least 3 biochemical processes for detoxifying this class of insecticide. Pyrethroid insecticides were developed in the 1970s as analogs of pyrethrum, a natural product of chrysanthemum flowers, known for its insecticidal properties for hundreds of years. Pyrethroids provide rapid knockdown of mosquitoes by binding to sodium channels on nerve cells and subsequently depolarizing them to stop neural transmission. Resistant mosquitoes are now capable of detoxifying pyrethroids by the above 3 biochemical processes and target cell insensitivity. Larvicides offer more target sites for killing immature mosquitoes, but increased tolerance or resistance has also been reported among different larvicide classes including the stomach poison Bacillus sphaericus, insect growth regulator (methoprene), and a commonly used OP (temephos) among some mosquito species

Laboratory And Field Assessment Of Some Kairomone Blends For Host-Seeking \u3ci\u3eAedes Aegypti\u3c/i\u3e

Using laboratory Y-tube olfactometers, the attractiveness of lactic acid and 2 kairomone blends from the United States Department of Agriculture (USDA) and BioGents GmbH (BG) was assessed for attractiveness to Aedes aegypti. Four geographically disparate populations were assessed: North Queensland Australia (NQA), Florida USA, Minas Gerais Brazil (MGB), and Singapore. In descending order, populations were attracted to USE)A, BG blends, and lactic acid. MGB was poorly attracted to lactic acid alone. The blends were less attractive than human odor. Proprietary blends were modified, and their attractiveness was assessed to find the optimum attractive mixture for NQA. Adding acetone to BG, and ammonia and caproic acid to USDA, improved attractiveness in the laboratory. Field attractiveness was assessed by coupling the blends with a newly developed BG-Sentinel Ae. aegypti trap. Trials were carried out using the BG blend, BG blend plus acetone, USDA blend, USDA blend plus ammonia and caproic acid, and a control trap with no kairomones. The traps were highly effective, with mean 24-h collections up to 11.15 Ae. aegypti per trap, and this species made up 91.7% of collections. However, the effectiveness of the unbaited control trap indicated that the BG-Sentinel has visual attractive properties for Ae. aegypti and that the kairomone lures added little to trap performance in NQA