Efficacy of α-Copaene, Cubeb, and Eucalyptol Lures for Detection of Redbay Ambrosia Beetle (Coleoptera: Curculionidae: Scolytinae)

Flora volatile profiles of plants visited by Vespa velutina: a preliminary assessment in the interaction of plant-insect

Plants function within complex ecological communities, relying on chemical signals to mediate interactions with other organisms. The foraging behaviour of insects, such as the invasive hornet Vespa velutina nigrithorax, introduced into northwestern Spain over a decade ago, may be influenced by floral volatiles. This hornet detects plant secondary metabolites, including semiochemicals, which aid in locating nectar, carbohydrates, prey, mating sites, and other resources. Understanding the volatile organic compounds (VOCs) emitted by plants visited by V. velutina may help to develop targeted control strategies. The aim of this study was to identify and analyse the volatile compounds emitted by 18 plant species frequented by V. velutina nigrithorax in the province of Ourense, northwest Spain. Solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used in this study. A total of 110 VOCs were identified, of which 21 compounds were abundant in the samples, with terpenes being the most abundant. Furthermore, a PLS-DA analysis selected 33 volatile compounds with variable importance scores (VIPs) greater than 1, in particular methylanthranilate with a value of 1.81. Eleven of these compounds were found to be abundant in the analysed samples, including (Z)-β-ocimene; 1-octen-3-ol; 3-hexen-1-ol, acetate, (Z)-; 3-octanone; eugenol; linalool; methyl salicylate; o-cymene; α-farnesene; α-terpineol and β-farnesene. The selection of these compounds provides valuable insights into plant-insect interactions, highlighting their diverse roles as plant volatiles in mediating insect behaviour and underlining their potential as targets for environmentally friendly pest management strategies.

The Biology, Impact, and Management of Xyleborus Beetles: A Comprehensive Review

Xyleborus beetles, a diverse group of ambrosia beetles, present challenges to forestry and agriculture due to their damaging burrowing behavior and symbiotic relationships with fungi. This review synthesizes current knowledge on the biology, ecology, and management of Xyleborus. We explore the beetles' life cycle, reproductive strategies, habitat preferences, and feeding habits, emphasizing their ecological and economic impacts. Control and management strategies, including preventive measures, chemical and biological control, and integrated pest management (IPM), are critically evaluated. Recent advances in molecular genetics and behavioral studies offer insights into genetic diversity, population structure, and host selection mechanisms. Despite progress, managing Xyleborus effectively remains challenging. This review identifies future research needs and highlights innovative control methods, such as biopesticides and pheromone-based trapping systems.

Comparison of ethanol-baited trap designs for ambrosia beetles in orchards in the eastern United States

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are among the most devastating pests of orchards, nurseries, and forests. Improving trap design and ethanol lures for capturing ambrosia beetles is necessary to develop effective monitoring and management strategies. In this 2-year study, we assessed 4 trap designs and 3 commercially formulated ethanol lures to refine trapping methods tailored for orchard environments in the eastern United States. Our investigation included orchards in 2 regions, Georgia (pecan orchards) and New York (apple orchards), targeting major ambrosia beetle (Coleoptera: Curculionidae) pest species such as Xylosandrus crassiusculus (Motschulsky), X. compactus (Eichhoff), X. germanus (Blandford), and Anisandrus maiche (Stark). Among the trap designs evaluated, clear sticky cards were most effective for capturing ambrosia beetles across orchard locations. Notably, in Georgia, sticky cards paired with specific low-release ethanol lures demonstrated enhanced capture of X. crassiusculus and X. compactus, 2 key ambrosia beetle pests found infesting young pecan trees. Similarly, in New York, sticky cards baited with low-release ethanol lures captured the highest rates of X. germanus and A. maiche, thus indicating its suitability for diverse ambrosia beetle populations. Overall, our study provides practical implications for tailoring trapping protocols to optimize ambrosia beetle management strategies in orchard settings.

Population changes of Bemisia tabaci (Hemiptera: Aleyrodidae) on different colored poinsettia leaves with different trichome densities and chemical compositions

The whitefly, Bemisia tabaci, is a destructive and invasive pest of many horticultural plants including poinsettia (Euphorbia pulcherrima). Outbreaks of B. tabaci cause serious damage by direct feeding on phloem sap, and spreading 100+ plant viruses to crops. Bemisia tabaci were observed more frequently on green than red poinsettia leaves, and the factors responsible for this are unknown. Here, we investigated the development rate, survivorship, fecundity of B. tabaci feeding on green versus red leaves, as well as the leaves' volatiles, trichome density, anthocyanin content, soluble sugars, and free amino acids. Compared to red leaves, B. tabaci on green leaves showed increased fecundity, a higher female sex ratio, and survival rate. The green color alone was more attractive to B. tabaci than red. Red leaves of poinsettia contained more phenol, and panaginsene in their volatiles. Alpha-copaene and caryophyllene were more abundant in the volatiles of poinsettia green leaves. Leaf trichome density, soluble sugars and free amino acids were higher in green than red leaves of poinsettia, anthocyanin was lower in green than red leaves. Overall, green leaves of poinsettia were more susceptible and attractive to B. tabaci. The morphological and chemical variation between red and green leaves also differed; further investigation may reveal how these traits affect B. tabaci's responses.

A New Repellent for Redbay Ambrosia Beetle (Coleoptera: Curculionidae: Scolytinae), Primary Vector of the Mycopathogen That Causes Laurel Wilt

The redbay ambrosia beetle, Xyleborus glabratus, was detected in Georgia, USA, in 2002 and has since spread to 11 additional states. This wood-boring weevil carries a symbiotic fungus, Harringtonia lauricola, that causes laurel wilt, a lethal disease of trees in the Lauraceae family. Native ambrosia beetles that breed in infected trees can acquire H. lauricola and contribute to the spread of laurel wilt. Since 2002, laurel wilt has devastated native Persea species in coastal forests and has killed an estimated 200,000 avocado trees in Florida. Since laurel wilt is difficult to manage once it has entered a susceptible agrosystem, this study evaluated piperitone as a candidate repellent to deter attacks by X. glabratus and other ambrosia beetles. Additionally, piperitone was compared to the known repellent verbenone as a potential cost-effective alternative. The repellent efficacy was determined by comparing captures in traps baited with commercial beetle lures containing α-copaene versus captures in traps baited with lures plus a repellent. In parallel 10-week field tests, the addition of piperitone reduced the captures of X. glabratus in α-copaene-baited traps by 90%; however, there was no significant reduction in the captures of native ambrosia beetles in ethanol-baited traps. In two replicate 10-week comparative tests, piperitone and verbenone both reduced X. glabratus captures by 68-90%, with longevity over the full 10 weeks. This study identifies piperitone as a new X. glabratus repellent with potential for pest management.

Community of Bark and Ambrosia Beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae) in Agricultural and Forest Ecosystems with Laurel Wilt

Redbay ambrosia beetle, Xyleborus glabratus, is an invasive wood-boring pest first detected in the USA in 2002 in Georgia. The beetle's dominant fungal symbiont, Harringtonialauricola, causes laurel wilt, a lethal disease of trees in the Lauraceae. Over the past 20 years, X. glabratus and laurel wilt have spread to twelve southeastern states, resulting in high mortality of native Persea species, including redbay (P. borbonia), swampbay (P. palustris), and silkbay (P. humilis). Laurel wilt also threatens avocado (P. americana) in south Florida, but in contrast to the situation in forests, X. glabratus is detected at very low levels in affected groves. Moreover, other species of ambrosia beetle have acquired H. lauricola and now function as secondary vectors. To better understand the beetle communities in different ecosystems exhibiting laurel wilt, parallel field tests were conducted in an avocado grove in Miami-Dade County and a swampbay forest in Highlands County, FL. Sampling utilized ethanol lures (the best general attractant for ambrosia beetles) and essential oil lures (the best attractants for X. glabratus), alone and in combination, resulting in detection of 20 species. This study documents host-related differences in beetle diversity and population levels, and species-specific differences in chemical ecology, as reflected in efficacy of lures and lure combinations.

Attraction and Longevity of 2- and 3-Component Food Cone Lures for the Caribbean Fruit Fly, Anastrepha suspensa (Diptera: Tephritidae)

The Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae), is a quarantine pest of Citrus spp. and a production pest of guava and other specialty fruits in Florida. Effective monitoring lures and traps are needed for early pest detection and timely initiation of control measures. As part of a continued effort to identify attractive synthetic lures for the Caribbean fruit fly, we conducted field tests in Homestead, Florida to compare the efficacy and longevity of commercial 2- and 3-component cone lures (2C [ammonium acetate and putrescine], 3C [ammonium acetate, putrescine, and trimethylamine]), the current standards used by regulatory agencies, versus the traditional liquid protein bait consisting of hydrolyzed torula yeast and borax as a positive control. Additional lures were also field-aged and periodically brought into the laboratory to quantify residual chemical contents. Traps baited with the torula yeast-borax mixture captured the highest mean number of A. suspensa, and traps baited with the commercial 2C lures captured more flies than the 3C lures. Traps baited with torula yeast-borax also captured the highest number of nontarget Diptera. Captures with all three treatments were significantly biased toward females. Attractiveness of the 2C lure began to drop after 6-8 wk, and the 3C lure after 5-6 wk. Overall, these data suggest that the 2C cone lure is more attractive to A. suspensa than the 3C cone lure under field conditions in south Florida, and that the 2C lures are attractive for up to 8 wk.

The Attractiveness of α-Copaene to Members of the Euwallacea fornicatus (Coleoptera: Curculionidae) Species Complex in California and Taiwan

Species belonging to the Euwallacea fornicatus Eichhoff (Coleoptera: Scolytinae) species complex have invaded the continental U.S. since at least 2003. Three species of this complex are known to have established, two in California (E. fornicatus; and Euwallacea kuroshio), and a third in Florida (Euwallacea perbrevis). Their native ranges are spread across southern and southeast Asia. In Taiwan, all three species occur in sympatry. They attack healthy trees of widely varied species and cause severe damage and death to the trees. The attractant quercivorol is commonly used to promote their detection by passive trapping. Recent studies in Florida have shown that trapping of E. perbrevis can be further improved by adding a synergist, α-copaene, alongside the quercivorol lure. Thus, we were interested in testing the effectiveness of α-copaene for trapping the other invasive members of the complex in California and in an area of Taiwan where all three species co-occur. We found that α-copaene marginally enhanced the trapping of E. perbrevis in Taiwan, but had no effect on the trapping of E. fornicatus or E. kuroshio in either California or Taiwan. We conclude that any enhancing effect of α-copaene is specific to E. perbrevis. This highlights the economic importance of accurate species identification in developing and implementing an efficient, and yet cost-effective, monitoring program for the management of E. fornicatus and E. kuroshio in California and elsewhere.

Comparison of Trap Designs for Detection of Euwallacea nr. fornicatus and Other Scolytinae (Coleoptera: Curculionidae) That Vector Fungal Pathogens of Avocado Trees in Florida

Laurel wilt and Fusarium dieback are vascular diseases caused by fungal symbionts of invasive ambrosia beetles (Coleoptera: Curculionidae: Scolytinae). Both diseases threaten avocado trees in Florida. Redbay ambrosia beetle, Xyleborus glabratus, is the primary vector of the laurel wilt pathogen, Raffaelea lauricola, but in recent years this symbiont has been transferred laterally to at least nine other species of ambrosia beetle, which now comprise a community of secondary vectors. Dieback disease, caused by Fusarium spp. fungi, is spread by shot hole borers in the Euwallacea fornicatus species complex. In this study, we conducted field tests in Florida avocado groves to compare efficacy of four trap designs for detection of Scolytinae. Treatments included an 8-funnel Lindgren trap, black 3-vane flight interception trap, green 3-vane interception trap, white sticky panel trap, and an unbaited sticky panel (control). In two tests targeting E. nr. fornicatus and X. glabratus, traps were baited with a two-component lure (α-copaene and quercivorol). In a test targeting other species, traps were baited with a low-release ethanol lure. For E. nr. fornicatus, sticky panels and black interception traps captured significantly more beetles than Lindgren traps; captures with green traps were intermediate. With ethanol-baited traps, 20 species of bark/ambrosia beetle were detected. Trap efficacy varied by species, but in general, sticky traps captured the highest number of beetles. Results indicate that sticky panel traps are more effective for monitoring ambrosia beetles than Lindgren funnel traps, the current standard, and may provide an economical alternative for pest detection in avocado groves.

Association of Pollinators of Different Species of Oil Palm with the Metabolic Profiling of Volatile Organic Compounds

The development of studies on emissions of volatile organic compounds (VOCs) by inflorescence of oil palms deserves a special attention regarding the importance to reproduction success and for increase of production. This study aimed to evaluate metabolic profiling of VOCs expelled by male and female inflorescences of different oil palm species (African oil palm, Amazonian Caiaué and the interspecific hybrid BRS-Manicoré), associating the composition variability with main pollinators to improve the comprehension of the plant-insect relationship. The phenylpropanoids, terpenoids and the aliphatic hydrocarbons were predominant classes detected in inflorescences of oil palms and the major compound was estragole. This result may be correlated with attraction of Elaidobius pollinators, since these insects were not attracted by Caiaué, which emitted estragole only in trace amounts. However, Caiaué and the hybrid species were visited by other native species whose frequencies were low and their success as pollinators could not be expected.

Utility of essential oils for development of host-based lures for Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), vector of laurel wilt

Redbay ambrosia beetle, Xyleborus glabratus, is native to Southeast Asia, but subsequent to introduction in Georgia in 2002, it has become a serious invasive pest in the USA, now established in nine southeastern states. Females vector Raffaelea lauricola, the fungus that causes laurel wilt, a lethal vascular disease of trees in the family Lauraceae. Laurel wilt has caused extensive mortality in native Persea species, including redbay (P. borbonia), swampbay (P. palustris), and silkbay (P. humilis). Avocado (P. americana) is now impacted in Florida, and with continued spread, laurel wilt has potential to affect avocado and native Lauraceae in California, Mexico, and throughout the American tropics. Effective lures for detection and control of X. glabratus are critical to slow the spread of laurel wilt. No pheromones are known for this species; primary attractants are volatile terpenoids emitted from host Lauraceae. This report provides a concise summary of the chemical ecology of X. glabratus, highlighting research to identify kairomones used by females for host location. It summarizes development of essential oil lures for pest detection, including discussions of the initial use of phoebe and manuka oil lures, the current cubeb oil lure, and a newly-developed distilled oil lure enriched in (-)-α-copaene.

Xyleborus bispinatus Reared on Artificial Media in the Presence or Absence of the Laurel Wilt Pathogen (Raffaelea lauricola)

Like other members of the tribe Xyleborini, Xyleborus bispinatus Eichhoff can cause economic damage in the Neotropics. X. bispinatus has been found to acquire the laurel wilt pathogen Raffaelea lauricola (T. C. Harr., Fraedrich & Aghayeva) when breeding in a host affected by the pathogen. Its role as a potential vector of R. lauricola is under investigation. The main objective of this study was to evaluate three artificial media, containing sawdust of avocado (Persea americana Mill.) and silkbay (Persea humilis Nash.), for rearing X. bispinatus under laboratory conditions. In addition, the media were inoculated with R. lauricola to evaluate its effect on the biology of X. bispinatus. There was a significant interaction between sawdust species and R. lauricola for all media. Two of the media supported the prolific reproduction of X. bispinatus, but the avocado-based medium was generally more effective than the silkbay-based medium, regardless whether or not it was inoculated with R. lauricola. R. lauricola had a neutral or positive effect on beetle reproduction. The pathogen was frequently recovered from beetle galleries, but only from a few individuals which were reared on inoculated media, and showed limited colonization of the beetle's mycangia. Two media with lower water content were most effective for rearing X. bispinatus.

Evaluation of Lure Combinations Containing Essential Oils and Volatile Spiroketals for Detection of Host-Seeking Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae)

The invasive redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), vectors the fungal pathogen (Raffaelea lauricola) that causes laurel wilt, a disease responsible for widespread mortality of trees in the Lauraceae in the southeastern United States. Early detection of incipient vector populations may allow for management practices that could successfully mitigate damage. Developing new, highly effective attractants is a priority for improving sensitivity of early detection efforts. In this study, two field tests were conducted to evaluate combinations of commercially available bark and ambrosia beetle lures for enhanced attraction of host-seeking female X. glabratus. In addition, lures were compared for capture of nontarget scolytine beetles. In the first experiment, traps baited with a combination of cubeb oil, conophthorin, chalcogran, and ethanol captured greater numbers of X. glabratus than cubeb oil alone, the current standard attractant. However, this combination lure resulted in higher nontarget scolytine captures than with the cubeb lure. In the second field test, an oil enriched in the sesquiterpene α-copaene caught significantly more X. glabratus than other lures currently available for monitoring this pest. There were no differences in efficacy between cubeb oil lures produced by two different manufacturers, and a combination lure containing copaiba and cubeb oils did not increase captures over the cubeb lure alone. Results of these two tests suggest that increased sensitivity for detection of X. glabratus may be achieved with a multicomponent lure that incorporates α-copaene, spiroketals, and low release of ethanol.

α-Copaene is an attractant, synergistic with quercivorol, for improved detection of Euwallacea nr. fornicatus (Coleoptera: Curculionidae: Scolytinae)

The tea shot-hole borer, Euwallacea fornicatus Eichhoff, is an ambrosia beetle endemic to Asia and a pest of commercial tea, Camellia sinensis (L.) Kuntze. Recently, a complex of species morphologically similar to E. fornicatus has been recognized, which includes new pests established in Israel and the USA, both in California and Florida. Collectively termed E. nr. fornicatus, these cryptic species carry symbiotic Fusarium spp. fungi, some of which cause dieback disease in susceptible hosts, which include avocado, Persea americana Miller. Due to the threat to this economically important crop, research was initiated to evaluate efficacy of kairomone-based lures for detection of the beetle in Florida (termed the Florida tea shot hole borer, FL-TSHB). A series of field tests were conducted in 2016 in commercial avocado groves known to have FL-TSHB at various population levels. All tests evaluated lures containing quercivorol (p-menth-2-en-1-ol) and α-copaene, presented separately and in combination; and one test evaluated effect of trap type on beetle captures. In addition, electroantennography (EAG) was used to quantify female olfactory responses to lure emissions. This study identified (-)-α-copaene as a new attractant for FL-TSHB, equivalent in efficacy to quercivorol (the standard lure for Euwallacea detection in the USA); however, the combination of lures captured significantly more FL-TSHB than either lure alone. This combination resulted in synergistic attraction at two field sites and additive attraction at a third site. Sticky panel traps captured more FL-TSHB than comparably-baited Lindgren funnel traps. Females engaged in host-seeking flight from 11:00 to 16:00 hr (EST), with peak numbers observed between 12:00 and 13:00 hr. EAG analyses confirmed olfactory chemoreception of both kairomones, with a higher response elicited with the combination of volatiles. Results indicate that detection of pest E. nr. fornicatus in Florida can be improved by using a two-component lure consisting of p-menth-2-en-1-ol and (-)-α-copaene.