Development of a female attractant for the click beetle pest Agriotes brevis

Perceptual Effects of Walnut Volatiles on the Codling Moth

The volatile organic compounds (VOCs) of plant hosts allow insect localization through olfactory recognition. In this study, the oviposition behavior of the codling moth was investigated and the VOCs from different walnut organs were extracted and analyzed to systematically study their composition and content differences. The electrophysiological and behavioral responses of the codling moth to walnut VOCs were measured using gas chromatography-electroantennographic detection (GC-EAD) and a four-arm olfactometer to screen the key active contents. The field investigation results indicated that 90.3% of the eggs spawned by the first generation of adult codling moths were adjacent to the walnut fruits. Walnut VOCs are mainly composed of terpenes, aromatics, and alkanes. Twelve VOCs can produce electroantennogenic (EAG) responses in the codling moths. Both adult males and females exhibit concentration dependence, with notable disparities in their EAG response levels. In the olfactory behavioral bioassay, linalool, eucalyptol, and high doses of geranyl acetate showed repellent effects on the codling moths, while myrcene, β-ocimene, nonanal, methyl salicylate, α-farnesene, and heptaldehyde showed the opposite. The relative levels of heptaldehyde, geranyl acetate, nonanal, and methyl salicylate were high in the fruits, which is intimately related to the localization of the walnut fruit by females. These VOCs can influence the oviposition behavior of codling moths but their application in the control of this pest needs to be confirmed and improved through further field experiments.

Pest Elaterids of North America: New Insights and Opportunities for Management

The larval stages of click beetle (Coleoptera: Elateridae) species, several of which are serious agricultural pests, are called wireworms. Their cryptic subterranean habitat, resilience, among-species differences in ecology and biology, and broad host range, as well as the lack of objective economic injury thresholds, have rendered wireworms a challenging pest complex to control. Significant progress has been made in recent years, introducing a new effective class of insecticides and improving species identification and our understanding of species-specific phenology, chemical ecology (i.e., adult sex pheromones and larval olfactory cues), and abiotic and biotic factors influencing the efficacy of biological control agents. These new developments have created opportunities for further research into improving our risk assessment, monitoring, and integrated pest management capabilities.

Field Evaluation of Selected Plant Volatiles and Conspecific Pheromones as Attractants for Agriotes obscurus and A. lineatus (Coleoptera: Elateridae)

Sex pheromones are commonly used in traps to monitor populations and movements of male click beetles, but to date few attractants have been identified for females. Notable exceptions are plant-derived kairomones for female Agriotes brevis and A. ustulatus, allowing the monitoring of both males and females of these species with lures containing both pheromones and plant volatiles. The attractiveness of these plant volatiles for two congeners, A. obscurus and A. lineatus, which are agricultural pests in Europe and North America, was evaluated in the current study. Both the four-component MINIM plant-derived lure for A. brevis, and the blend of (E)-anethol and (E)-cinnamaldehyde for A. ustulatus, were not attractive to A. obscurus and A. lineatus, and instead appeared to reduce captures—both when compared to blank controls, and when blended with and compared to the sex pheromones of these species. This was most pronounced in A. obscurus, where (E)-anethol and (E)-cinnamaldehyde reduced male captures by 43 and 37%, respectively. Combining the pheromones of A. obscurus and A. lineatus reduced captures of these species by 77 and 19%, respectively, compared to these pheromones singly. This suggests that attractants for female click beetles can be highly species-specific, and that the blending of pheromones of congeneric species with each other, or with plant volatiles, can reduce captures. Further research into developing such attractants for economic species is urgently needed.

Assessment of the Attraction Range of Sex Pheromone Traps to Agriotes (Coleoptera, Elateridae) Male Click Beetles in South-Eastern Europe

Simple Summary

Click beetles are the adults of wireworms, soil-dwelling larvae that damage multiple arable crops. The attraction range of YATLORf pheromone traps to click beetles of four species of Agriotes wireworms was studied to provide additional information about the implementation of integrated pest management against these harmful pests in Europe. This should allow a significant reduction in insecticide use. Male click beetles were marked and released at different distances from a pheromone trap. Recapture rate, maximum sampling ranges, and effective sampling areas were calculated. The recapture rate was significantly affected by distance, species, and wind direction and decreased as distance increased. The majority of beetles were caught from short distances (up to 10 m) within the first five days. The estimated attraction range was low for all the considered Agriotes species, suggesting that pheromone traps were unsuitable for use as mass trapping instruments to disrupt mating. However, after results and previous research outputs were evaluated, it seems possible to use the traps not only as monitoring tools, but also as attract-and-kill strategies for most beetle populations.

Abstract

The attraction range of YATLORf pheromone traps to adults of four species of Agriotes (A. brevis, A. sordidus, A. litigiosus, and A. ustulatus) was studied to provide additional information about the most harmful Agriotes species in Europe. Male click beetles were marked and released at different distances from a pheromone trap. The recapture rate was calculated and analyzed using analysis of variance. The recapture rate was significantly affected by distance, species, and wind direction. The recapture rate decreased as distance increased. The majority of beetles were caught from short distances (up to 10 m) within the first five days. A. brevis, a mainly crawling species, showed the lowest recapture rate. The wind direction affected the recovery rate, with a significantly lower number of beetles moving downwind from the release points. Maximum sampling ranges and effective sampling areas were calculated. The obtained estimations were low (53 to 86 m and 509 to 2602 m², respectively) for all the considered Agriotes species, suggesting that they were unsuitable for use as mass trapping instruments to disrupt mating. However, it seems possible to use the traps not only as monitoring tools, but also as attract-and-kill strategies for most beetle populations.

An update of the Worldwide Integrated Assessment (WIA) on systemic pesticides. Part 4: Alternatives in major cropping systems

We present a synthetic review and expert consultation that assesses the actual risks posed by arthropod pests in four major crops, identifies targets for integrated pest management (IPM) in terms of cultivated land needing pest control and gauges the implementation "readiness" of non-chemical alternatives. Our assessment focuses on the world's primary target pests for neonicotinoid-based management: western corn rootworm (WCR, Diabrotica virgifera virgifera) in maize; wireworms (Agriotes spp.) in maize and winter wheat; bird cherry-oat aphid (Rhopalosiphum padi) in winter wheat; brown planthopper (BPH, Nilaparvata lugens) in rice; cotton aphid (Aphis gossypii) and silver-leaf whitefly (SLW, Bemisia tabaci) in cotton. First, we queried scientific literature databases and consulted experts from different countries in Europe, North America, and Asia about available IPM tools for each crop-pest system. Next, using an online survey, we quantitatively assessed the economic relevance of target pests by compiling country-level records of crop damage, yield impacts, extent of insecticide usage, and "readiness" status of various pest management alternatives (i.e., research, plot-scale validation, grower-uptake). Biological control received considerable scientific attention, while agronomic strategies (e.g., crop rotation), insurance schemes, decision support systems (DSS), and innovative pesticide application modes were listed as key alternatives. Our study identifies opportunities to advance applied research, IPM technology validation, and grower education to halt or drastically reduce our over-reliance on systemic insecticides globally.

The Addition of a Pheromone to a Floral Lure Increases Catches of Females of the Click Beetle Agriotes ustulatus (Schaller) (Coleoptera: Elateridae)

Agriotes ustulatus is an economically important click beetle in Europe. A female-produced pheromone, (E,E)-farnesyl acetate, has been identified and is used for monitoring and detecting males. More recently, a floral lure targeting females with modest, but significant, activity has been described. Based on preliminary data, we hypothesized, that similar to the effects on the congeneric A. brevis, addition of the pheromone to the floral lure should improve female A. ustulatus catches. Also, as click beetles have been reported to respond to white light, we studied possible interactions between visual and chemical cues. In field trials, the addition of the synthetic pheromone to the floral lure resulted in a dramatic increase in the number of females trapped, whereas male catches remained unaffected and equal to those in traps baited with pheromone only. A white visual cue did not influence trap catches. Maximum catches of both sexes of A. ustulatus can be achieved using the pheromone and the floral lure inside the same trap. Furthermore, the compounds can be formulated in a single polyethylene bag dispenser, making handling of the trap easier. Due to a much larger proportion of females in the catch, this improved trap may be a promising tool for semiochemical-based, environmentally sound agricultural practice against this important pest.

Effects of Chemical Insecticide Imidacloprid on the Release of C6 Green Leaf Volatiles in Tea Plants (Camellia sinensis)

Chemical insecticides are widely used for pest control worldwide. However, the impact of insecticides on indirect plant defense is seldom reported. Here, using tea plants and the pesticide imidacloprid, effects of chemical insecticides on C₆-green leaf volatiles (GLVs) anabolism and release were investigated first time. Compared with the non-treated control plants, the treatment of imidacloprid resulted in the lower release amount of key GLVs: (Z)-3-hexenal, n-hexenal, (Z)-3-hexene-1-ol and (Z)-3-Hexenyl acetate. The qPCR analysis revealed a slight higher transcript level of the CsLOX3 gene but a significantly lower transcript level of CsHPL gene. Our results suggest that imidacloprid treatment can have a negative effect on the emission of GLVs due to suppressing the critical GLVs synthesis-related gene, consequently affecting plant indirect defense.

Design of an Attractant for Empoasca onukii (Hemiptera: Cicadellidae) Based on the Volatile Components of Fresh Tea Leaves

The tea leafhopper, Empoasca onukii Matsuda, is a serious pest of the tea plant. E. onukii prefers to inhabit vigorously growing tender tea leaves. The host selection of E. onukii adults may be associated with plant volatile compounds (VOCs). We sought to identify potentially attractive VOCs from tea leaves at three different ages and test the behavioral responses of E. onukii adults to synthetic VOC blends in the laboratory and field to aid in developing an E. onukii adult attractant. In darkness, the fresh or mature tea leaves of less than 1-mo old could attract more leafhoppers than the mature branches (MB) that had many older leaves (leaf age >1 mo). Volatile analysis showed that the VOC composition of the fresh leaves was the same as that of the mature leaves, but linalool and indole were not at detectable levels in VOCs from the MB. Moreover, the mass ratio differed for each common volatile in the three types of tea leaves. When under competition with volatiles from the MB, the leafhoppers showed no significant tropism to each single volatile but could be attracted by the synthetic volatile blend imitating the fresh leaves. With the removal of some volatile components, the effective synthetic volatile blend was mixed with (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, and linalool at a mass ratio of 0.6:23:12.6. These three volatiles may be the key components for the host selection of E. onukii adults and could be used as an attractant in tea gardens.

Conspecific and Heterogeneric Lacewings Respond to (Z)-4-Tridecene Identified from Chrysopa formosa (Neuroptera: Chrysopidae)

Green lacewings (Chrysopidae) are predators of soft-bodied pest insects and are among the most important biological control agents in crop protection. Chrysopa spp. are of special importance since, unlike most green lacewing species, adults are also predatory. The current study was undertaken in search of Chrysopa formosa compounds with semiochemical activity. Using coupled gas chromatography-electroantennography (GC-EAG), head and thorax extracts of C. formosa elicited EAG responses to a compound subsequently identified by coupled GC/mass spectrometry, microchemistry, chemical synthesis and GC peak enhancement as (Z)-4-tridecene. In field experiments, this compound decreased attraction of adult C. formosa to (1R,4aS,7S,7aR)-nepetalactol and that of Chrysoperla carnea species-complex to a ternary floral lure, with the inhibitory effect found to be dose-dependent. Our results suggest that (Z)-4-tridecene may serve as a general warning signal among multiple green lacewing species. Perspectives for potential practical applications are discussed.