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Laurel wilt and Fusariumdieback 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 Fusariumspp. fungi, is spread by shot hole borers in the Euwallacea fornicatusspecies 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. fornicatusand 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.

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, SSUand beta-tubulin datasets the most prominent phenotypes were Raffaelea lauricola(cause of laurel wilt), R. subalba, R. subfusca, R. fusca, R. arxiiand an undescribed Raffaeleasp. Mean numbers of colony forming units (CFUs) of R. lauricolavaried 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.

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.

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.

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 α-copaene, α-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.

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.

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.

Current ammonia-based lures vary considerably in their ability to attract Anastrepha fruit flies in the field. This report presents results from electroantennography (EAG) and behavioral bioassays that examined the effect of age on fly response to ammonia and carbon dioxide, two volatile chemicals released from commercial ammonium bicarbonate lures. EAG measurements from female Caribbean fruit flies, Anastrepha suspensa (Loew), showed that ammonia generated a greater EAG response in sexually immature females compared with mature females. Conversely, carbon dioxide elicited stronger EAG responses in sexually mature females. In flight tunnel bioassays, females from both age groups were captured in response to ammonia ranging from 60 to 3840 µg/h, but captures declined with increasing ammonia concentration. In bioassays with the two highest ammonia release rates, captures of immature females were significantly lower than captures of mature females. Carbon dioxide, ranging from 300 to 7200 µg/h, did not capture any flies when presented alone in the flight tunnel bioassay. However, for sexually mature flies, carbon dioxide in combination with ammonia was more attractive than ammonia alone. These age-related differences in response to ammonia and carbon dioxide may account for some of the variability observed in field tests with ammonium bicarbonate lures.