Attraction of the redbay ambrosia beetle, Xyleborus glabratus, to avocado, lychee, and essential oil Lures

The redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is an exotic wood-boring insect that vectors the mycopathogen responsible for laurel wilt, a lethal vascular disease of trees in the Lauraceae. High mortality has occurred in native Persea species in the southeastern U.S., and the vector-pathogen complex poses an imminent threat to the production of commercial avocado, P. americana, in south Florida. There is a critical need for effective attractants to detect, monitor, and control this invasive pest. This study combined field tests and laboratory bioassays to evaluate the response of female X. glabratus to host-based volatiles from wood of avocado (cultivars of West Indian, Guatemalan, and Mexican races); from wood of lychee (Litchi chinensis, a presumed non-host that is high in the sesquiterpene α-copaene, a putative attractant); and to commercial lures containing manuka and phoebe oils, two reported attractive baits. Volatile collections and GC-MS analyses were performed to quantify the sesquiterpene content of test substrates. In the field, traps baited with lychee wood captured more beetles than those with wood from avocado cultivars; traps baited with phoebe oil lures captured more beetles than those with manuka oil lures (the current monitoring tool). In field and laboratory tests, X. glabratus did not show a preference among avocado races in either attraction or host acceptance (initiation of boring). In choice tests, lychee was more attractive than avocado initially, but a higher percentage of beetles bored into avocado, suggesting that lychee emits more powerful olfactory/visual cues, but that avocado contains more of the secondary cues necessary for host recognition. Emissions of α-copaene, β-caryophyllene, and α-humulene were correlated with field captures, and lychee wood may be a source of additional semiochemicals for X. glabratus.

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.

Distribution, Pest Status and Fungal Associates of Euwallacea nr. fornicatus in Florida Avocado Groves

Members of a complex of cryptic species, that correspond morphologically to the ambrosia beetle Euwallacea fornicatus (Eichhoff) (Coleoptera: Curculionidae: Scolytinae), were recently found attacking avocado (Persea americana Mill.) in Israel and California. In early 2016, an outbreak of another member of this species complex was detected infesting approximately 1500 avocado trees in an avocado orchard at Homestead, Florida. An area-wide survey was conducted in commercial avocado groves of Miami-Dade County, Florida to determine the distribution and abundance of E. nr. fornicatus, to identify different populations of E. nr. fornicatus and their fungal associates, and to assess the extent of damage to avocado trees. Ewallacea nr. fornicatus were captured in 31 of the 33 sampled sites. A sample of 35 beetles from six different locations was identified as E. nr. fornicatus sp. #2, which is genetically distinct from the species causing damage in California and Israel. Eleven fungal associates were identified: an unknown Fusarium sp., AF-8, AF-6, Graphium euwallaceae, Acremonium sp. Acremonium morum, Acremonium masseei, Elaphocordyceps sp. and three yeast species. The unknown Fusarium isolates were the most abundant and frequently found fungus species associated with adult beetles and lesions surrounding the beetle galleries. In addition to fungal associates, three bacteria species were found associated with adult E. nr. fornicatus. Visual inspections detected significant damage in only two orchards. A large number of beetles were captured in locations with no apparent damage on the avocado trees suggesting that E. nr. fornicatus are associated with other host(s) outside the groves or with dead trees or branches inside the groves. More research is needed to determine the potential threat E. nr. fornicatus and its fungal associates pose to the avocado industry and agricultural and natural ecosystems in Florida.

Attraction and electroantennogram responses of male Mediterranean fruit fly to volatile chemicals from Persea, Litchi and Ficus wood

Trimedlure is the most effective male-targeted lure for the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). A similar response is elicited by plant substances that contain α-copaene, a naturally-occurring sesquiterpene. α-Copaene is a complex, highly-volatile, widely-distributed plant compound, and male C. capitata respond to material from both hosts (e.g., Litchi chinensis) and non-hosts (e.g., Ficus benjamina) that contain α-copaene. Avocado, Persea americana, recently was found to contain varying amounts of α-copaene in the bark and underlying cambial tissue. Short-range attraction bioassays and electroantennography (EAG) were used to quantify responses of sterile male C. capitata to samples of rasped wood from four avocado genotypes, L. chinensis, and F. benjamina. Gas chromatography-mass spectral (GC-MS) analysis was used to identify and quantify the major sesquiterpenes. Attraction and EAG amplitude were correlated, with L. chinensis eliciting the highest and F. benjamina the lowest responses. Responses to the avocado genotypes were intermediate, but varied among the four types. GC-MS identified 13 sesquiterpenes, including α-copaene, from all samples. Amounts of α-copaene in volatile collections from samples (3 g) ranged from 11.8 μg in L. chinensis to 0.09 μg in F. benjamina, which correlated with short-range attraction and EAG response. α-Copaene ranged from 8.0 to 0.8 μg in the avocado genotypes, but attraction and EAG responses were not correlated with the amount of α-copaene. Differences in enantiomeric structure of the α-copaene in the different genotypes and/or presence of additional sesquiterpenes may be responsible for the variation in male response. EAG responses were correlated with the amount of several other sesquiterpenes including α-humulene, and this compound elicited a strong antennal response when tested alone.

North American Lauraceae: terpenoid emissions, relative attraction and boring preferences of redbay ambrosia beetle, Xyleborus glabratus (coleoptera: curculionidae: scolytinae)

The invasive redbay ambrosia beetle, Xyleborus glabratus, is the primary vector of Raffaelea lauricola, a symbiotic fungus and the etiologic agent of laurel wilt. This lethal disease has caused severe mortality of redbay (Persea borbonia) and swampbay (P. palustris) trees in the southeastern USA, threatens avocado (P. americana) production in Florida, and has potential to impact additional New World species. To date, all North American hosts of X. glabratus and suscepts of laurel wilt are members of the family Lauraceae. This comparative study combined field tests and laboratory bioassays to evaluate attraction and boring preferences of female X. glabratus using freshly-cut bolts from nine species of Lauraceae: avocado (one cultivar of each botanical race), redbay, swampbay, silkbay (Persea humilis), California bay laurel (Umbellularia californica), sassafras (Sassafras albidum), northern spicebush (Lindera benzoin), camphor tree (Cinnamomum camphora), and lancewood (Nectandra coriacea). In addition, volatile collections and gas chromatography-mass spectroscopy (GC-MS) were conducted to quantify terpenoid emissions from test bolts, and electroantennography (EAG) was performed to measure olfactory responses of X. glabratus to terpenoids identified by GC-MS. Significant differences were observed among treatments in both field and laboratory tests. Silkbay and camphor tree attracted the highest numbers of the beetle in the field, and lancewood and spicebush the lowest, whereas boring activity was greatest on silkbay, bay laurel, swampbay, and redbay, and lowest on lancewood, spicebush, and camphor tree. The Guatemalan cultivar of avocado was more attractive than those of the other races, but boring response among the three was equivalent. The results suggest that camphor tree may contain a chemical deterrent to boring, and that different cues are associated with host location and host acceptance. Emissions of α-cubebene, α-copaene, α-humulene, and calamenene were positively correlated with attraction, and EAG analyses confirmed chemoreception of terpenoids by antennal receptors of X. glabratus.

Chemical Characterization and Biological Activity of the Mastic Gum Essential Oils of Pistacia lentiscus Var. Chia from Turkey

The essential oils (EOs) were isolated by hydrodistillation from wild and cultivated Pistacia lentiscus L. var. chia-mastic gum tree (Anacardiaceae) from two natural habitats, namely from Cesme-Uzunkoy (1) and Mordogan (2), and one cultivated source, Cesme-Germiyan (3), in Izmir, Turkey. This comparative study evaluated the chemical composition and biological activity of mastic gum essential oils (MGEOs). For this purpose, MGEOs 1-3 were analyzed by gas chromatography-flame ionization detection (GC-FID), gas chromatography-mass spectrometry (GC-MS), and chiral GC for α-pinene. Laboratory assays were conducted to assess for potential in vitro cytotoxicity (multiple in vitro cancer cell lines), antimicrobial properties (five bacterial species and yeast), anti-inflammatory activity (inhibition of inducible nitric oxide synthase, iNOS), and the attraction of Ceratitis capitata (Mediterranean fruit fly, medfly), respectively. Chemical analysis indicated that MGEOs 1 and 2 were rich in α-pinene (56.2% and 51.9%), myrcene (20.1% and 18.6%), and β-pinene (2.7% and 3.1%), respectively; whereas MGEO-3 was characterized by a high level of α-pinene (70.8%), followed by β-pinene (5.7%) and myrcene (2.5%). Chiral GC analyses showed that concentration ratios between (-)/(+)-α-pinene and (-)-α-pinene/myrcene allowed for differentiation between wild and cultivated MGEO sources. In biological assays, MGEOs 1-3 did not exhibit significant antimicrobial effects against the pathogens evaluated and were not strong attractants of male medflies; however, all three MGEOs displayed a dose-dependent inhibition of iNOS, and MGEOs 1 and 2 exhibited selective in vitro cytotoxicity against human cancer cells. These results suggest that wild-type mastic gum oils from Cesme and Mordogan (MGEOs 1 and 2) are potential sources of beneficial products and warrant further investigation.

Rearing Xyleborus volvulus (Coleoptera: Curculionidae) on Media Containing Sawdust from Avocado or Silkbay, With or Without Raffaelea lauricola (Ophiostomatales: Ophiostomataceae)

Like other ambrosia beetles, Xyleborus volvulus Fabricius (Coleoptera: Curculionidae) lives in a mutualistic symbiotic relationship with fungi that serve as food source. Until recently, X. volvulus was not considered a pest, and none of its symbionts were considered plant pathogens. However, recent reports of an association between X. volvulus and Raffaelea lauricola T.C. Harr., Fraedrich & Aghayeva (Ophiostomatales: Ophiostomataceae), the cause of the laurel wilt disease of avocado (Persea americana Mill. [Laurales: Lauraceae]), and its potential role as vector of the pathogen merit further investigation. The objective of this study was to evaluate three artificial media containing sawdust obtained from avocado or silkbay (Persea humilis Nash) for laboratory rearing of X. volvulus. The effect of R. lauricola in the media on the beetle's reproduction was also evaluated. Of the three media, the one with the lowest content of sawdust and intermediate water content provided the best conditions for rearing X. volvulus. Reproduction on this medium was not affected by the sawdust species or the presence of R. lauricola. On the other two media, there was a significant interaction between sawdust species and R. lauricola. The presence of R. lauricola generally had a negative effect on brood production. There was limited colonization of the mycangia of X. volvulus by R. lauricola on media inoculated with the pathogen. From galleries formed within the best medium, there was 50% recovery of R. lauricola, but recovery was much less from the other two media. Here, we report the best artificial substrate currently known for X. volvulus.

Xyleborus glabratus, X. affinis, and X. ferrugineus (Coleoptera: Curculionidae: Scolytinae): electroantennogram responses to host-based attractants and temporal patterns in host-seeking flight

The redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is an exotic wood-boring insect that vectors the mycopathogen responsible for laurel wilt, a lethal vascular disease of trees in the Lauraceae, including avocado (Persea americana Mill.). Effective semiochemical-based detection and control programs for X. glabratus will require an understanding of the chemical ecology and host-seeking behaviors of this new invasive pest. This study 1) presents an electroantennography (EAG) method developed for assessment of olfactory responses in ambrosia beetles; 2) uses that new method to quantify EAG responses of X. glabratus, X. affinis, and X. ferrugineus to volatiles from three host-based attractants: manuka oil (essential oil extract from Leptospermum scoparium Forst. & Forst.), phoebe oil (extract from Phoebe porosa Mex.), and wood from silkbay (Persea humilis Nash); and 3) documents temporal differences in host-seeking flight of the sympatric Xyleborus species. Field observations revealed that X. glabratus engages in flight several hours earlier than X. affinis and X. ferrugineus, providing a window for selective capture of the target pest species. In EAG analyses with X. glabratus, antennal response to phoebe oil was equivalent to response to host Persea wood, but EAG response elicited with manuka oil was significantly less. In comparative studies, EAG response of X. glabratus was significantly higher than response of either X. affinis or X. ferrugineus to all three host-based substrates. Future research will use this EAG method to measure olfactory responses to synthetic terpenoids, facilitating identification of the specific kairomones used by X. glabratus for host location.

Geographic variation in mycangial communities of Xyleborus glabratus

Factors that influence fungal communities in ambrosia beetle mycangia are poorly understood. The beetle that is responsible for spreading laurel wilt in SE USA, Xyleborus glabratrus, was examined at three sites along a 500 km N-S transect in Florida, each populated by host trees in the Lauraceae. Fungal phenotypes were quantified in mycangia of individual females that were collected from a site in Miami-Dade County (MDC), 25.8N, with swamp bay (Persea palustris), one in Highlands County (HC), 27.9N, with silkbay (P. humulis) and swamp bay and another in Alachua County (AC), 29.8N, with redbay (P. borbonia). Based on combined LSU, SSU and beta-tubulin datasets the most prominent phenotypes were Raffaelea lauricola (cause of laurel wilt), R. subalba, R. subfusca, R. fusca, R. arxii and an undescribed Raffaelea sp. Mean numbers of colony forming units (CFUs) of R. lauricola varied by location (P < 0.003), and a multivariate analysis, which accounted for the presence and relative abundance of fungal species, indicated that there were significant variations in mycangial communities among the sites; thus climate and vegetation might have affected fungal diversity and the relative abundance of these fungi in the mycangia of X. glabratus Statistically it was unlikely that any of the species influenced the presence and prevalence of another species.

Monitoring insect pests in retail stores by trapping and spatial analysis

Stored-product insects are a perennial problem in retail stores, where they damage and contaminate susceptible merchandise such as food products and animal feed. Historically, pest management in these stores has relied heavily on chemical insecticides, but environmental and health issues have dictated use of safer methods, and these require better monitoring. A monitoring procedure that employs an array of moth and beetle traps combined with spatial (contour) analysis of trap catch was tested in three department stores and two pet stores. The rate of capture increased with the level of infestation but was essentially constant over 4- to 5-d trapping periods. Contour analysis effectively located foci of infestation and reflected population changes produced by applications of the insect growth regulator (S)-hydroprene. The most abundant insects were Plodia interpunctella (Hiibner), Lasioderma serricorne (F.), Oryzaephilus mercator (Fauvel), Tribolium castaneum (Herbst), and Cryptolestes pusillus (Schönherr). The results indicate that contour analysis of trap counts provides a useful monitoring tool for management of storage pests in retail stores. It identifies trouble spots and permits selection, timing, and precision targeting of control measures to achieve maximum pest suppression with minimum pesticide risk. It permits managers and pest control operators to visualize pest problems over an entire store, to monitor changes over time, and to evaluate the effectiveness of control intervention. The contour maps themselves, along with records of control applications and stock rotation, provide permanent documentation of pest problems and the effectiveness of pest management procedures.

Temporal analysis of sesquiterpene emissions from manuka and phoebe oil lures and efficacy for attraction of Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae)

Redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is an exotic wood-borer that vectors the fungal agent (Raffaelea lauricola) responsible for laurel wilt. Laurel wilt has had severe impact on forest ecosystems in the southeastern United States, killing a large proportion of native Persea trees, particularly redbay (P. borbonia) and swampbay (P. palustris), and currently poses an economic threat to avocado (P. americana) in Florida. To control the spread of this lethal disease, effective attractants are needed for early detection of the vector. Two 12-wk field tests were conducted in Florida to evaluate efficacy and longevity of manuka and phoebe oil lures, and to relate captures of X. glabratus to release rates of putative sesquiterpene attractants. Two trap types were also evaluated, Lindgren funnel traps and sticky panel traps. To document lure emissions over time, a separate set of lures was aged outdoors for 12 wk and sampled periodically to quantify volatile sesquiterpenes using super-Q adsorbant and gas chromatography-mass spectroscopy analysis. Phoebe lures captured significantly more X. glabratus than manuka lures, and sticky traps captured more beetles than funnel traps. Phoebe lures captured X. glabratus for 10-12 wk, but field life of manuka lures was 2-3 wk. Emissions of alpha-copaene, alpha-humulene, and cadinene were consistently higher from phoebe lures, particularly during the 2-3 wk window when manuka lures lost efficacy, suggesting that these sesquiterpenes are primary kairomones used by host-seeking females. Results indicate that the current monitoring system is suboptimal for early detection of X. glabratus because of rapid depletion of sesquiterpenes from manuka lures.

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.

Electroantennogram and behavioral responses of Anastrepha suspensa (Diptera: Tephritidae) to putrescine and ammonium bicarbonate lures

At present, the most effective synthetic lures for pest Anastrepha fruit flies are multicomponent blends that include ammonia and the diamine synergist putrescine (1,4-diaminobutane). Both chemicals generally have been regarded as protein cues that result in female-biased attraction. Using electroantennography (EAG) and flight tunnel bioassays, this study evaluated response of the Caribbean fruit fly, Anastrepha suspensa (Loew) to vapors released from commercial lure formulations of ammonium bicarbonate and putrescine. Over a range of doses tested, EAG response to ammonium bicarbonate was equivalent for both sexes, but female response was significantly greater than male response to putrescine and to a 1:1 mixture of ammonium bicarbonate and putrescine. Amplitude of EAG response to the mixture was approximately equal to the summation of responses to the individual substrates. Using a fixed dose of substrate, EAG measurements from females 1-14 d old indicated that antennal sensitivity to both lures varied according to physiological state of the fly. Peak response to ammonium bicarbonate was recorded from immature females, peak response to putrescine from sexually mature females. In bioassays, more females were captured with ammonium bicarbonate plus putrescine than with ammonium bicarbonate alone. This difference was not observed in males, resulting in a higher female to male ratio in captures with ammonium bicarbonate plus putreseine (3:1) versus ammonium bicarbonate alone (1:1). Results suggest that separate olfactory receptors are involved in detection of the two semiochemicals, and that the putrescine component is primarily responsible for the female-biased attraction.

Cubeb Oil Lures: Terpenoid Emissions, Trapping Efficacy, and Longevity for Attraction of Redbay Ambrosia Beetle (Coleoptera: Curculionidae: Scolytinae)

Redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is an exotic wood borer and the primary vector of Raffaelea lauricola, a symbiotic fungus that causes laurel wilt. This lethal disease has decimated native redbay [Persea borbonia (L.) Sprengel] and swampbay [Persea palustris (Rafinesque) Sargent] throughout southeastern U.S. forests, and currently threatens avocado (Persea americana Miller) in Florida. To curtail the spread of laurel wilt, effective attractants are needed for early detection of the vector. Phoebe oil lures were the best known attractant for X. glabratus, but they are no longer available. The current detection system uses manuka oil lures, but previous research indicated that manuka lures have a short field life in Florida. Recently, cubeb oil was identified as a new attractant for X. glabratus, and cubeb bubble lures are now available commercially. This study compared trapping efficacy and field longevity of cubeb and manuka lures with phoebe lures that had been in storage since 2010 over a 12-wk period in south Florida. In addition, terpenoid emissions were quantified from cubeb and manuka lures aged outdoors for 12 wk. Captures were comparable with all three lures for 3 wk, but by 4 wk, captures with manuka were significantly less. Equivalent captures were obtained with cubeb and phoebe lures for 7 wk, but captures with cubeb were significantly greater from 8 to 12 wk. Our results indicate that cubeb bubble lures are the most effective tool currently available for detection of X. glabratus, with a field life of 3 months due to extended low release of attractive sesquiterpenes, primarily α-copaene and α-cubebene.

Ethyl Formate as a Methyl Bromide Alternative for Fumigation of Citrus: Efficacy, Fruit Quality, and Workplace Safety

Ethyl formate (EF) was evaluated as a potential alternative to methyl bromide (MB) for phytosanitary treatment of imported citrus fruit in the Republic of Korea. Planococcus citri (Risso) (Hemiptera: Pseudococcidae), a mealybug with known tolerance against EF and MB, was used as a representative pest to test efficacy of the two fumigants against eggs. In nine commercial-scale refrigerated container (67.5 m3) trials using imported orange, lemon and grapefruit, EF applied at the currently approved dose for citrus (70 g·m-3 at 5°C for 4 h, developed for Aspidiotus excisus Green (Hemiptera: Diaspididae), a species less EF tolerant than P. citri) resulted in 76.9-98.3% mortality of P. citri eggs. The EF treatment did not affect the sugar content or the color of peel and pulp of the treated fruit. When oranges were treated according to the current MB (64 g·m-3 at >5°C for 2 h) or EF treatment guidelines, the concentration of fumigant around the fruit fluctuated between 9.4 and 185.1 ppm for EF and 9.5-203.0 ppm for MB during the 72-h post-fumigation processes (venting [0-2 h], transportation to storage [2-24 h], and storage periods [24-72 h]) with both EF and MB maintained between 10 and 100 ppm during the storage period. Considering the efficacy of EF, its apparent lack of phytotoxicity, and its more manageable threshold limit value for humans (100 ppm EF compared to 1 ppm MB for an 8-h time weighted average exposure), our results suggest that EF may be a promising alternative to MB for the phytosanitary treatment of imported citrus in Korea.

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.

HPTLC Analysis and Chemical Composition of Selected Melaleuca Essential Oils

Tea tree oil (TTO) is a volatile essential oil obtained by distillation, mainly from the Australian native plant Melaleuca alternifolia (Maiden & Betche) Cheel (Myrtaceae). In this study, a comparative analysis of the chemical constituents of seven tea tree oils (M. alternifolia) and four other Melaleuca spp. oils (M. cajuputi, (M_Ca), two chemotypes of M. quinquenervia, (M_Ne and M_Ni), and M. ericifolia (M_Ro)) was carried out using gas chromatography-mass spectrometry (GC-MS) and high-performance thin-layer chromatography (HPTLC). Among the seven TTOs, terpinen-4-ol (37.66-44.28%), γ-terpinene (16.42-20.75%), α-terpinene (3.47-12.62%), α-terpineol (3.11-4.66%), and terpinolene (2.75-4.19%) were the most abundant compounds. On the other hand, the most abundant compounds of the other Melaleuca oils varied, such as 1,8-cineole (64.63%) in M_Ca oil, (E)-nerolidol (48.40%) and linalool (33.30%) in M_Ne oil, 1,8-cineole (52.20%) in M_Ni oil, and linalool (38.19%) and 1,8-cineole (27.57%) in M_Ro oil. HPTLC fingerprinting of Melaleuca oils enabled the discrimination of TTO oils from other Melaleuca spp. oils. Variation was observed in the profile of the R_f values among EOs. The present study shows that HPTLC is one of the best ways to identify and evaluate the quality control in authenticating TTOs, other Melaleuca EOs, or EOs from other species within the Myrtaceae.

Response of Anastrepha suspensa (Diptera: Tephritidae) to terminal diamines in a food-based synthetic attractant

A current trapping system for Anastrepha fruit flies uses a two-component food-based synthetic attractant consisting of ammonium acetate and putrescine (1,4-diaminobutane). Development of more effective monitoring programs may be realized through identification of additional attractant chemicals. This study examined response of the Caribbean fruit fly, Anastrepha suspensa (Loew), to putrescine and four homologous terminal diamines, differing only in carbon chain length. Using a fixed dose of each diamine substrate, electroantennogram (EAG) responses from mature females to putrescine and cadaverine (1,5-diaminopentane) were not significantly different from each other but were significantly greater than responses to longer chain diamines. Over a range of doses tested, mean female EAG response was greater than male response to both putrescine and cadaverine. In an initial field test, capture of female flies in traps baited with ammonium acetate and either putrescine or cadaverine was higher than in traps baited with ammonium acetate and any of the other diamines. In a subsequent field test, traps baited with putrescine, cadaverine, or 1,6-diaminohexane in combination with ammonium acetate captured more female flies than traps baited with ammonium acetate alone. A significantly greater synergistic effect on female captures was observed with either putrescine or cadaverine than with 1,6-diaminohexane. Thus, of the diamines evaluated, cadaverine elicited both antennal and behavioral responses comparable to that of putrescine and will be studied further as a potential attractant for pest Anastrepha species.

Insecticidal and Attractant Activities of Magnolia citrata Leaf Essential Oil against Two Major Pests from Diptera: Aedes aegypti (Culicidae) and Ceratitis capitata (Tephritidae)

In this study, Magnolia citrata Noot and Chalermglin (Magnoliaceae) essential oil (MCEO) was evaluated for insecticidal activity against the yellow fever mosquito Aedes aegypti and attractant activity for the Mediterranean fruit fly Ceratitis capitata. The leaves of Magnolia citrata (Giổi chanh) were collected from northwestern Vietnam, and the water-distilled MCEO was analyzed by gas-chromatography and mass spectrometry (GC-MS). The major constituents of MCEO were identified as linalool 19%, geranial 16%, citronellal 14%, neral 14%, and sabinene 12%. MCEO showed 100% mortality at 1 μg/μL against 1st instar larvae of Ae. aegypti (Orlando strain, ORL), and the oil exhibited 54% (ORL) and 68% (Puerto Rico strain) mortality at 5 μg/mosquito against Ae. aegypti adult females. Initial screens showed that MCEO had weak insecticidal activity compared to the positive control permethrin. In bioassays with sterile male C. capitata, MCEO exhibited moderately strong attraction, comparable to that observed with a positive control, Tetradenia riparia essential oil (TREO). Herein, the insecticidal and attractant activities of MCEO are reported for the first time.

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

Redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is a wood-boring pest that has now invaded nine states in the southeastern United States. The beetle's dominant fungal symbiont (Raffaelea lauricola) is phytopathogenic, inducing laurel wilt in trees within the family Lauraceae. Members of the genus Persea are particularly susceptible to the lethal disease, including native redbay (P. borbonia) and swampbay (P. palustris), as well as commercial avocado (P. americana). Cubeb oil lures are the current standard for detection of X. glabratus, but recently eucalyptol and a 50% α-copaene oil have been identified as additional attractants. This study used a combination of binary-choice bioassays, field cage release-and-recapture assays, and a 12-wk field trial to compare efficacy of eucalyptol and copaene lures relative to commercial cubeb lures. In addition, GC-MS was used to quantify emissions from lures field-aged for 12 wk. In laboratory bioassays, copaene lures were more attractive than eucalyptol lures. In field cage assays, copaene lures recaptured a higher percentage of released beetles than cubeb lures. In the field test, cubeb lures captured fewer beetles than copaene lures, and lowest captures were obtained with eucalyptol lures. Combining eucalyptol with either copaene or cubeb lures did not increase captures over those lures deployed alone. Both copaene and cubeb lures were effective in attracting X. glabratus for 12 wk, but field life of eucalyptol lures was only 4 wk, consistent with the quantification of lure emissions. Results suggest that the 50% α-copaene lure provides the best pest detection currently available for X. glabratus.

Quantification of ammonia release from fruit fly (Diptera: Tephritidae) attractants using infrared spectroscopy

Ammonia is the primary attractant for tephritid fruit flies, and traps baited with synthetic attractants using ammonia formulations have been highly successful in capturing these pests. However, difficulties in quantifying release rates of ammonia have limited abilities to make comparisons among field tests of different species by using different formulations. Therefore, Fourier transform infrared (FTIR) spectroscopy was evaluated as a method to quantify ammonia from synthetic lures. Analysis of the headspace from commercial ammonium bicarbonate and ammonium acetate lures indicated that there is a large burst of ammonia liberated upon initial exposure of the lures, but after 5-7 d the release rates stabilize and remain steady for at least 60 d under laboratory conditions. During the period of steady release, FTIR st atic measurements showed a n average of 0.12 and 0.21 microg of ammonia per 50-ml sample from ammonium bicarbonate and ammonium acetate lures, respectively. FTIR dynamic measurements from ammonium acetate lures indicated a steady release rate of approximately 200 microg/h. Ammonia release rate from ammonium acetate lures could be reduced by decreasing the surface area of the release membrane, and the presence of crystal formations on the membrane seemed to decrease the longevity of the ammonium acetate lures.

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.