Use Of Semiochemicals Research Articles

Use of Semiochemicals for the Management of the Redbay Ambrosia Beetle.

Simple SummaryLaurel wilt is a devastating exotic fungal disease that threatens avocado and related members of the laurel family in North America. This disease has killed over 300 million redbay trees and has caused cascading ecological impacts across the landscape. Management strategies, especially in natural forests, are limited. The ambrosia beetles that vector this disease respond strongly to odors produced by the trees, and our research indicates that it is possible to repel the beetles away from trees in a forest setting with the use of verbenone. Other compounds have been identified that can be used to trap the beetles. If used together, these strategies can be used to develop a single “push-pull” system to manage this disease in natural systems where other management strategies are not feasible.This review highlights current advances in the management of the redbay ambrosia beetle, Xyleborus glabratus, a primary vector of the pathogenic fungus, Raffaelea lauricola, that causes laurel wilt. Laurel wilt has a detrimental effect on forest ecosystems of southeastern USA, with hundreds of millions of Lauraceae deaths. Currently, preventive measures mostly focus on infected-tree removal to potentially reduce local beetle populations and/or use of preventative fungicide applications in urban trees. Use of semiochemicals may offer an opportunity for the management of X. glabratus. Research on attractants has led to the development of α-copaene lures that are now the accepted standards for X. glabratus sampling. Research conducted on repellents first included methyl salicylate and verbenone and attained significant reduction in the number of X. glabratus captured on redbay and swamp bay trees treated with verbenone. However, the death rate of trees protected with verbenone, while lower compared to untreated trees, is still high. This work underscores the necessity of developing new control methods, including the integration of repellents and attractants into a single push-pull system.

Insect pests of the Herbarium of the Palermo botanical garden and evaluation of semiochemicals for the control of the key pest Lasioderma serricorne F. (Coleoptera: Anobiidae)

The herbaria are scientific tools of great importance that preserve extinct, rare, endemic, and common plant species and also have importance as Cultural Heritage for their historical and esthetical value. Herbaria can be infested by several insect pests feeding on dried plants, and their management is often complicated and difficult as the use of chemical insecticides can have negative drawbacks. This suggests a strong need for alternative control tools such as the use of semiochemicals to develop Integrated Pest Management (IPM) programs. In order to identify the main insect pests that determine the damages on the exsiccata stored in the Palermo Botanical Garden's Herbarium, one of the largest in the world, a survey of the botanical samples and their infestations was carried out. The survey pointed out that Lasioderma serricorne was the key pest of the herbarium. Consequently, experiments were conducted to evaluate and optimize the use of semiochemicals for monitoring and mass trapping L. serricorne. Two sex pheromone dispensers (polyethylene tubes and patch dispensers, made by tissue-not tissue glued with pheromone) were evaluated for their efficacy in terms of emission and insect attraction. A food attractant, Capsicum annuum dried fruit powder, was also evaluated as synergist of the pheromone. Results indicated that polyethylene tubes determined a pheromone emission more constant with time and attracted a higher number of insects in traps in comparison with patch dispensers. Moreover, the use of C. annuum fruit powder in the pheromone traps determined a significant increase of catches compared with the traps loaded with pheromone alone, suggesting the possibility that accumulation or synergist effects occur.

A Review of Interactions between Insect Biological Control Agents and Semiochemicals.

Biological control agents and semiochemicals have become essential parts of the integrated pest management of insect pests over recent years, as the incorporation of semiochemicals with natural enemies and entomopathogenic microbials has gained significance. The potential of insect pheromones to attract natural enemies has mainly been established under laboratory conditions, while semiochemicals from plants have been used to attract and retain natural enemies in field conditions using strategies such as trap crops and the push–pull mechanism. The best-known semiochemicals are those used for parasitoids–insect pest–plant host systems. Semiochemicals can also aid in the successful dispersal of entomopathogenic microbials. The use of semiochemicals to disseminate microbial pathogens is still at the initial stage, especially for bacterial and viral entomopathogens. Future studies should focus on the integration of semiochemicals into management strategies for insects, for which several semiochemical compounds have already been studied. More effective formulations of microbial agents, such as granular formulations of entomopathogenic fungi (EPFs), along with bio-degradable trap materials, could improve this strategy. Furthermore, more studies to evaluate species-specific tactics may be needed, especially where more than one key pest is present.

First Report on Identification of Volatiles from Egg and Larval Frass of Indian Strain of the American Bollworm Helicoverpa armigera (Hübner)

Globally Helicoverpa armigera, a polyphagous pest of many economic crops, has developed resistance to almost all groups of insecticides presently in used for its control. In cotton, its larvae cause severe damage and feeds on all plant parts including young leaves, square, flowers and bolls which in turn cause economic damage. Recent reports on development of its resistance to transgenic cotton which has Cry1Ac and Cry2Ab (Bt cotton) has given an indication of future threat to cotton growers. Therefore, use of semiochemicals as management strategy for these insects would be a great alternative as ethological pest management within insect pest management (IPM) to control this menace. These semiochemicals/volatile organic compounds can be present in insect (egg, larva, female) as well as in the host plant. In the present study, a total of seven volatiles have been identified from methanol extract of eggs and faecal pellets, out of which two volatiles; methyl ester of octadecanoic acid (methyl stearate) and methyl ester of hexadecanoic acid (methyl palmatate), were detected in egg samples. From faecal pellets five volatiles were identified namely octadecanoic acid (stearic acid) and its methyl ester, hexadecanoic acid (palmitic acid) and its methyl ester, tetradecanoic acid (myristic acid), caryophyllene and its oxide, phytol. Interestingly, methyl ester of octadecanoic acid and methyl ester of hexadecanoic acid were detected in both the samples. Volatiles observed in common may be used as effective semiochemicals in ethological pest management of Helicoverpa armigera. However, further study is needed to validate the competency of these fatty acids under field conditions.

Nitrogenous compounds characterized in the deterrent skin extract of migratory adult sea lamprey from the Great Lakes region

The sea lamprey (Petromzons marinus) is a devastating invasive species that represents a significant impediment to restoration of the Laurentian Great Lakes. There is substantial interest in developing environmentally benign control strategies for sea lamprey, and many other aquatic invasive species, that employ the manipulation of semiochemical information (pheromones and chemical cues) to guide the movements of invaders into control opportunities (e.g. traps, locations for safe pesticide application, etc.). A necessary precursor to the use of semiochemicals in conservation activities is the identification of the chemical constituents that compose the odors. Here, we characterize the major nitrogenous substances from the water-soluble fraction of a skin extract that contains the sea lamprey alarm cue, a powerful repellent that has proven effective in guiding the movements of migrating sea lamprey in rivers. Nitrogenous compounds are suspected components of fish alarm cues as the olfactory sensory neurons that mediate alarm responses transduce amino acids and related compounds. A laboratory assay confirmed the behavioral activity contained in the alarm cue resides in the water-soluble fraction of the skin extract. This water-soluble fraction consisted primarily of creatine (70%), heterocyclic nitrogenous compounds (4.3%) and free amino acids (18.4%), respectively. Among the free amino acids characterized in our study, essential amino acids constituted 13% of the water-soluble fraction. Free amino acids isolated from the water-soluble fraction composed of arginine, phenylalanine, threonine, and asparagine 3.9, 2.7, 2.6 and 2.4% of the water-soluble fraction, respectively. We discuss the implications of these findings for understanding the nature and use of the sea lamprey alarm cue in conservation activities.

Identification of a non-host semiochemical from tick-resistant donkeys (Equus asinus) against Amblyomma sculptum ticks

Amblyomma sculptum is a tick affecting animal and human health across Argentina, Bolivia, Paraguay and Brazil. Donkeys, Equus asinus, are known to be resistant to A. sculptum, suggesting that they can produce non-host tick semiochemicals (allomones), as already demonstrated for some other vertebrate host/pest interactions, whereas horses, Equus caballus, are considered as susceptible hosts. In this study, we tested the hypothesis that donkeys produce natural repellents against A. sculptum, by collecting sebum from donkeys and horses, collecting the odour from sebum extracts, and identifying donkey-specific volatile compounds by gas chromatography (GC) and coupled GC-mass spectrometry (GC–MS). From the complex collected blends, five main compounds were identified in both species. Hexanal, heptanal and (E)-2-decenal were found predominantly in donkey extracts, whilst ethyl octanoate and ethyl decanoate were found predominantly in horse extracts. One compound, (E)-2-octenal, was detected exclusively in donkey extracts. In Y-tube olfactometer bioassays 36 different A. sculptum nymphs were tested for each extract, compound and concentration. The dry sebum extracts and the compounds identified in both species induced neither attraction nor repellency. Only (E)-2-octenal, the donkey-specific compound, displayed repellency, with more nymphs preferring the arm containing the solvent control when the compound was presented in the test arm across four concentrations tested (p < 0.05, Chi-square test). A combination of a tick attractant (ammonia) and (E)-2-octenal at 0.25 M also resulted in preference for the control arm (p < 0.05, Chi-square test). The use of semiochemicals (allomones) identified from less-preferred hosts in tick management has been successful for repelling brown dog ticks, Rhipicephalus sanguineus sensu lato from dog hosts. These results indicate that (E)-2-octenal could be used similarly to interfere in tick host location and be developed for use in reducing A. sculptum numbers on animal and human hosts.

Convergent evolution of semiochemicals across Kingdoms: bark beetles and their fungal symbionts

Convergent evolution of semiochemical use in organisms from different Kingdoms is a rarely described phenomenon. Tree-killing bark beetles vector numerous symbiotic blue-stain fungi that help the beetles colonize healthy trees. Here we show for the first time that some of these fungi are able to biosynthesize bicyclic ketals that are pheromones and other semiochemicals of bark beetles. Volatile emissions of five common bark beetle symbionts were investigated by gas chromatography-mass spectrometry. When grown on fresh Norway spruce bark the fungi emitted three well-known bark beetle aggregation pheromones and semiochemicals (exo-brevicomin, endo-brevicomin and trans-conophthorin) and two structurally related semiochemical candidates (exo-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane and endo-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane) that elicited electroantennogram responses in the spruce bark beetle Ips typographus. When grown on malt agar with 13C d-Glucose, the fungus Grosmannia europhioides incorporated 13C into exo-brevicomin and trans-conophthorin. The enantiomeric compositions of the fungus-produced ketals closely matched those previously reported from bark beetles. The production of structurally complex bark beetle pheromones by symbiotic fungi indicates cross-kingdom convergent evolution of signal use in this system. This signaling is susceptible to disruption, providing potential new targets for pest control in conifer forests and plantations.

The Potential use of Semiochemicals in Pest Suppression

The Potential use of Semiochemicals in Pest Suppression

Decoding of chemical communication in insect pests and its manipulation for their management in citrus (Citrus spp.)

The semio-chemicals in general have environmental benefits associated with their use, in contrast to conventional insecticides. These semio-chemicals are inherently different from synthetic insecticides in terms of their mode of action and subsequent impact on the environment and human health. Although a number of outstanding successes have proved the potential of pheromone technology, the use of semio-chemicals is still in its early stages in India. It can be safely predicted that, as farming practices, the demand for semio-chemical technology will increase steadily which requires continuous and equal efforts of researchers, industry and farmers. Development of semio-chemical based push pull strategies using pheromones, repellents of insect pests and attractants of bio-agents for the management of insect pests in citrus (Citrus spp.) and citrus based farming systems needs immediate attention as these are known to be eco-friendly insect pest management strategies.

Identification, Expression Patterns, and Functional Characterization of Chemosensory Proteins in Dendroctonus armandi (Coleoptera: Curculionidae: Scolytinae).

The Chinese white pine beetle, Dendroctonus armandi Tsai and Li (Coleoptera: Curculionidae: Scolytinae), is a serious pest of coniferous forests in China. Thus, there is considerable interest in developing eco-friendly pest-control methods, with the use of semiochemicals as a distinct possibility. Olfaction is extremely important for fitness of D. armandi because it is the primary mechanism through which the insect locates hosts and mates. Thus, here we characterized nine full-length genes encoding chemosensory proteins (CSPs) from D. armandi. The genes were ubiquitously and multiply expressed across different developmental stages and adult tissues, indicating various roles in developmental metamorphosis, olfaction, and gustation. Ligand-binding assays implied that DarmCSP2 may be the carrier of D. armandi pheromones and various plant host volatiles. These volatiles were identified through RNA interference of DarmCSP2 as: (+)-α-pinene, (+)-β-pinene, (−)-β-pinene, (+)-camphene, (+)-3-carene, and myrcene. The systematic chemosensory functional analysis of DarmCSP2 in this study clarified the molecular mechanisms underlying D. armandi olfaction and provided a theoretical foundation for eco-friendly pest control.

Semiochemical Exploitation of Host-Associated Cues by Seven Melittobia Parasitoid Species: Behavioral and Phylogenetic Implications

Chemical compounds (infochemicals or semiochemicals) play an important role both in intra-specific and inter-specific communication. For example, chemical cues appear to play a key role in the host selection process adopted by insect parasitoids. In recent years significant advances have been made in order to understand the chemical ecology of insect parasitoids. However, little information is available about the evolution of semiochemical use in the host location process of insect parasitoids. Here we investigated the strategy adopted by seven closely related parasitoid species in the genus Melittobia when foraging for four different suitable hosts. By using an integrated approach that combined olfactometer bioassays and phylogenetic investigations, we found that: 1) exploitation of host-derived semiochemicals is widespread in the Melittobia genus; 2) there is specificity of attraction towards the different host species tested; in particular, the early-branching species in the Melittobia genus are attracted to odors associated with leaf cutting bees (Megachile rotundata) whereas the most-diverged species are attracted to odors associated with solitary mud dauber wasps (Trypoxyilon politum). Regardless of the phylogenetic relationships, no Melittobia species exhibited attraction towards odors of factitious laboratory hosts (i.e. the flesh fly Sarcophaga bullata). Interestingly, five Melittobia species are also attracted by odors associated with honeybees hosts which indicate that these parasitoids could be potential pests of honeybees. Our study shed light on the host location within the Melittobia genus and represents a first attempt to understand semiochemical use in an evolutionary perspective in the context of parasitoids’ foraging behavior.

Chemical Composition of the Low-Polar Fraction of the Copitarsia uncilata Burgos & Leiva (Lepidoptera: Noctuidae) Eversible Pheromone Gland.

In Colombia, Copitarsia uncilata Burgos & Leiva has been reported as a pest of ornamental flowers. The leafworm causes serious economic losses to farmers because the shipments are intercepted at the detection sites. The identification and subsequent synthesis of the sex pheromone compounds can lead to the use of semiochemicals as an important strategy to complement the pest management. This paper identifies and characterizes the chemical components of the female sexual gland of C. uncilata at three different age stages in order to relate the effect of age on the gland extract composition. Eggs and larvae were collected from commercial crops. The specimens were reared and sexed. Pheromone glands of intact females were excised at (a) 1-2, (b) 3-4, and (c) 5-6days old. The extracts were analyzed using GC-MS after two extraction time points: 20min and 8days. The extracts from the third age stage showed an increase in concentration for 35% of the compounds after 8days of storage. The relative abundance as a function of the female age showed two trends: an upward trend, where the relative abundances of the compounds increased through the age stages, while some compounds shown a downward trend. Within the first trend, mostly of the compounds were found to be related with infochemicals type structures, where tetradec-9-en-1-yl acetate (within several C-14 long-chain alcohols) is the main one. The 9-14:Ac quadrupled concentration through the ages is possibly related to the increased length of calling period as female moth age.

Ambrosia Beetle (Coleoptera: Curculionidae: Scolytinae) Captures Using Colored Traps in Southeast Tennessee and South Mississippi

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) have become a major impediment to profitable nursery production, with proper controls centered around an accurate monitoring program. Whereas the use of semiochemicals by ambrosia beetles is well understood, the potential use of visual cues including colors remains relatively understudied. Field tests were performed in Tennessee and Mississippi to determine response of the ambrosia beetle community to 13 trap colors (black, blue, brown, clear, gray, green, lavender, opaque, orange, purple, red, white, and yellow). Traps consisted of corrugated plastic in the shape of a prism and covered in insect glue (Pestick™ or Tangle-Trap®). All trap colors were analyzed with a spectro-photometer to quantify spectral reflectance, ranging from 6 - 80% reflectance. Mean ambrosia beetle capture from opaque and red traps (60 and 54, respectively) was significantly higher than from yellow or white traps (30 and 28, respectively). However, captures from each of the afore-mentioned 4 colors were not significantly different from the other 9 colors tested. Although further research is needed to explain the efficacy of the opaque traps, we can recommend that industry-standard black traps are an acceptable choice for ambrosia beetle monitoring programs; whereas, yellow or white traps are not recommended.

Field response of Hylastinus obscurus Marsham (Coleoptera: Curculionidae) to E-2-hexenal and limonene, two host-derived semiochemicals

L. Parra, A. Mutis, F. Ortega, and A. Quiroz. 2013. Field response of Hylastinus obscurus Marsham (Coleoptera: Curculionidae) to E-2-hexenal and limonene, two host-derived semiochemicals. Cien. Inv. Agr. 40(3): 637-642. Red clover (Trifolium pratense L.), a valuable legume in Chile, is important mainly for seed production and as forage for animal production. Although it is considered a perennial, the productivity of this legume declines during the second year of growth primarily because of infestation by the red clover root borer, Hylastinus obscurus (Coleoptera: Curculionidae). Currently, there is no efficient method for controlling this insect, although the use of semiochemicals may provide a new alternative to reduce the damage caused by this curculionid. In this context, E-2-hexenal and limonene, which were previously determined to be an attractant and a repellent, respectively, for H. obscurus, were released from dispensers established in two cultivars (Quinequeli INIA and Superqueli INIA) and one experimental line (Syn II Pre III) of red clover at the Centro Regional de Investigacion Carillanca (INIA-Carillanca) (Vilcun, Chile). H. obscurus was found in significantly higher numbers on plants from areas treated with E-2-hexenal than from areas treated with limonene or in areas that were left untreated as control areas. However, this attractiveness was influenced by the red clover source such that the effect of E-2-hexenal was observed in Superqueli INIA and Syn II Pre III but not in Quinequeli INIA. Unlike previous studies, limonene had no effect on H. obscurus. Our results provide the first evidence under field conditions for the potential use of E-2-hexenal as an attractant for the red clover root borer H. obscurus.

Chemicals, Climate, and Control: Increasing the Effectiveness of Malaria Vector Control Tools by Considering Relevant Temperatures

Malaria vector control currently relies almost exclusively on killing adult mosquitoes with chemical insecticides. Insecticide-treated nets (ITNs), long-lasting insecticide-treated nets (LLINs), and indoor residual sprays (IRS) aim to repel, disable, and/or kill mosquitoes on contact. While these tools have proven to be extremely successful in reducing disease incidence and mortality [1], insecticide resistance is on the rise and a resurgence of malaria is feared [2]. To mitigate the effects of resistance, the development of new insecticides and formulations for use in LLINs and for IRS remains a research priority [3]. In this paper we argue that, to increase the effectiveness of the chemical arsenal available, we need to consider the relevant microclimatic conditions in which these tools are deployed. We will discuss how temperature in particular can interact with the conventional use of chemicals within houses, and broaden our discussion to consider its potential influence on the use of semiochemicals to lure mosquitoes to traps.

Symposium 9: Rocky Mountain Futures: Preserving, Utilizing, and Sustaining Rocky Mountain Ecosystems

Symposium 9: Rocky Mountain Futures: Preserving, Utilizing, and Sustaining Rocky Mountain Ecosystems

Effects of non‐host plant odour on Meligethes aeneus during immigration to oilseed rape

AbstractThe use of semiochemicals for the manipulation of the pollen beetle, Meliethes aeneus (Fabricius) (Coleoptera: Nitidulidae), is being investigated for potential incorporation into a push‐pull strategy for this pest, which damages oilseed rape, Brassica napus L. (Brassicaceae), throughout Europe. Previous laboratory behavioural studies using volatiles from non‐host plants showed that M. aeneus is repelled by the odour of lavender, Lavendula angustifolia Mill. (Lamiaceae), essential oil. This article reports on semi‐field and field trials to investigate this behaviour under more realistic conditions. Semi‐field experiments were conducted to assess the relative importance of olfaction at different points in host location behaviour by M. aeneus. The results showed that oilseed rape plants treated with lavender odour were less colonised by M. aeneus in comparison with an untreated control, but that the treatment effect was much reduced if the lavender odour was applied after colonisation. The field experiment demonstrated that lavender odour caused a significant reduction in the number of adult M. aeneus infesting the oilseed rape plants in the treatment plots compared to the control plots. Overall, these findings are very encouraging for the future development of a push‐pull pest control system.

Modern perspectives on stored-product insect pest management

Introduction Modern perspectives of stored-product insect pest management are represented here by nine topics which fall into three broad categories: sampling, insecticide resistance and management practices. The three insect sampling papers cover techniques for detecting insects and estimating insect population densities to decide whether pest management is needed. The first of the resistance papers covers the sublethal effects of insecticides and behavioural resistance, areas that are often overlooked when evaluating effectiveness of insecticides against insect pests associated with stored commodities. The other resistance paper describes the historical background and current perspectives on the only national resistance surveillance and management programs in the world. Three of the four pest management papers cover specialised pest management methods such as use of semiochemicals, insect-resistant packaging or treatment of packaged products with modified atmospheres, and use of elevated temperatures. The last paper gives a current overview of the status of stored-product insect pest management in Africa using biological, chemical and physical methods, and sheds light on challenges and current needs for improved pest management.

Pheromone Communication in Nasonia vitripennis: Abdominal Sex Attractant Mediates Site Fidelity of Releasing Males

Males of the parasitic wasp Nasonia vitripennis (Hymenoptera: Pteromalidae) use a substrate-borne sex pheromone to attract virgin females. The pheromone is synthesized in the rectal vesicle and deposited via the anus by dabbing movements of the abdominal tip. The chemicals attracting the females are composed of a mixture (4R,5R- and (4R,5 S)-5-hydroxy-4-decanolides (HDL) being synergized by the trace component 4-methylquinazoline (4-MeQ) which is not attractive for females when offered alone. Here we show that male pheromone deposits are not only attractive to virgin females but also for the releasing males themselves. In an olfactometer bioassay, males were strongly attracted by their own pheromone markings but were unable to discriminate between their own markings and those deposited by other males. Polar fractions of pheromone gland extracts containing the HDLs and 4-MeQ were also highly attractive for males. Bioassays using synthetic pheromones in natural doses revealed that combinations of HDL/4-MeQ and 4-MeQ alone attracted males whereas the HDLs alone were behaviorally inactive. Furthermore, males did not discriminate between HDL/4-MeQ and 4-MeQ alone. We conclude that the trace component 4-MeQ mediates site fidelity of N. vitripennis males at sites previously marked with the abdominal sex pheromone. The use of 4-MeQ to stay at and to return to scent-marked patches rather than marking new ones might be a strategy to economize semiochemical use in N. vitripennis males.

Evaluation of Attractants to Improve Trapping Success of Nutria on Louisiana Coastal Marsh

ABSTRACT Nutria (Myocastor coypus) are an important part of the Louisiana (USA) fur industry, but high densities of nutria cause extensive damage to coastal marsh ecosystems. Hence, there is a need to develop improved methods for targeted management of nutria. We screened 14 olfactory cues as potential lures for nutria, first in controlled settings and then in the field, to see if nutria capture rates using foothold traps would increase. In Y‐maze trials, nutria most frequently selected olfactory cues of a synthetic formulation of nutria anal‐gland secretion and nutria fur extract. We examined the 3 most selected attractants in Y‐maze trials and female nutria urine under field conditions to compare trapping success over untreated traps. Capture probability was nearly 2.5 times greater for fur wash than control and 2 times greater for urine than control (relative risk = 2.43 and 2.01, respectively). The results suggest that use of semiochemicals and synthetic formulations of semiochemicals increased nutria trapping success. Development and use of effective synthetic semiochemicals could benefit resource managers nationwide who are responsible for reducing damage caused by this invasive herbivore.