Terpenoid variations within and among half-sibling avocado trees, Persea americana Mill. (Lauraceae).

Chemical analyses were conducted to determine the qualitative and quantitative differences in monoterpenes and sesquiterpenes in plant material from avocado trees, Persea americana Mill. (Lauraceae). The initial study analyzed plant material sampled from the trunk to the leaves through different branch diameters to quantify proximo-distal spatial differences within a tree. All trees were seedlings initiated from a single maternal tree. Two-way analysis of variance was conducted on 34 chemicals that comprised at least 3% of the total chemical content of at least one tree and/or location within a tree. There were significant interactions between genotype and location sampled for most chemicals. Parentage analysis using microsatellite molecular markers (SSR's) determined that the four trees had three fathers and that they represented two full-siblings and two half-sibling trees. Descriptive discriminant analysis found that both genotype and location within a tree could be separated based on chemical content, and that the chemical content from full-siblings tended to be more similar than chemical content from half-siblings. To further explore the relationship between genetic background and chemical content, samples were analyzed from leaf material from 20 trees that included two sets of full-sibling seedling trees, the maternal tree and the surviving paternal tree. Descriptive discriminant analysis found good separation between the two full-sibling groups, and that the separation was associated with chemistry of the parental trees. Six groups of chemicals were identified that explained the variation among the trees. We discuss the results in relation to the discrimination process used by wood-boring insects for site-selection on host trees, for tree selection among potential host trees, and the potential use of terpenoid chemical content in chemotaxonomy of avocado trees.

Efficacy of wax matrix bait stations for Mediterranean fruit flies (Diptera: Tephritidae).

Tests were conducted that evaluated efficacy of wax matrix bait stations for Ceratitis capitata (Wiedemann) adults in Guatemala. Bait stations were exposed to outdoor conditions to determine effect of weathering on longevity as indicated by bait station age. Results of laboratory tests found that bait stations with spinosad and ammonium acetate remained effective for at least 31 d compared with pesticide-free controls, although there was some loss of efficacy over time. Percentage mortality for bait station strips with 2% spinosad and 1% ammonium acetate decreased from 100 +/- 0.0% on day 0 to 70 +/- 7.1% after 31 d. Ammonia concentration had little effect on percentage mortality although there was some indication that ammonia concentration affected number of flies observed on the bait stations. Bait station strips (one per cage) were more effective than controls for 6-8 wk when tests were conducted in field cages (3 m diameter x 2 m), but only 2-3 wk when tests were conducted in large (2.5 m high and 6.0 m wide and 7.5 m long) field cages. Longevity was restored when multiple bait stations (3, 6, or 12) were deployed per cage. Bait stations containing methomyl were used for field tests of efficacy for wild flies. Dipped lure bait stations, which were made by coating two edges of commercial ammonium acetate and trimethylamine lures, killed six times more flies than corn cob bait stations dipped into a Nulure/malathion solution. They also killed more flies than pesticide-free controls for 8 wk.

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.

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, ß-caryophyllene, and α-humulene were correlated with field captures, and lychee wood may be a source of additional semiochemicals for X. glabratus.

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.

Effective sampling range of a synthetic protein-based attractant for Ceratitis capitata (Diptera: Tephritidae).

Studies were conducted in Honduras to determine effective sampling range of a female-targeted protein-based synthetic attractant for the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Multilure traps were baited with ammonium acetate, putrescine, and trimethylamine lures (three-component attractant) and sampled over eight consecutive weeks. Field design consisted of 38 traps (over 0.5 ha) placed in a combination of standard and high-density grids to facilitate geostatistical analysis, and tests were conducted in coffee (Coffea arabica L.),mango (Mangifera indica L.),and orthanique (Citrus sinensis X Citrus reticulata). Effective sampling range, as determined from the range parameter obtained from experimental variograms that fit a spherical model, was approximately 30 m for flies captured in tests in coffee or mango and approximately 40 m for flies captured in orthanique. For comparison, a release-recapture study was conducted in mango using wild (field-collected) mixed sex C. capitata and an array of 20 baited traps spaced 10-50 m from the release point. Contour analysis was used to document spatial distribution of fly recaptures and to estimate effective sampling range, defined by the area that encompassed 90% of the recaptures. With this approach, effective range of the three-component attractant was estimated to be approximately 28 m, similar to results obtained from variogram analysis. Contour maps indicated that wind direction had a strong influence on sampling range, which was approximately 15 m greater upwind compared with downwind from the release point. Geostatistical analysis of field-captured insects in appropriately designed trapping grids may provide a supplement or alternative to release-recapture studies to estimate sampling ranges for semiochemical-based trapping systems.

Effective sampling range of food-based attractants for female Anastrepha suspensa (Diptera: Tephritidae).

Release-recapture studies were conducted with both feral and sterile females of the Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae), to determine sampling range for a liquid protein bait (torula yeast/borax) and for a two-component synthetic lure (ammonium acetate and putrescine). Tests were done in a guava, Psidium guajava L., grove and involved releasing flies at a central point and recording the numbers captured after 7 h and 1, 2, 3, and 6 d in an array of 25 Multilure traps located 9-46 m from the release point. In all tests, highest rate of recapture occurred within the first day of release, so estimations of sampling range were based on a 24-h period. Trap distances were grouped into four categories (<10, 10-20, 20-30, and >30 m from release point) and relative trapping efficiency (percentage of capture) was determined for each distance group. Effective sampling range was defined as the maximum distance at which relative trapping efficiency was > or = 25%. This corresponded to the area in which 90% of the recaptures occured. Contour analysis was also performed to document spatial distribution of fly dispersal. In tests with sterile flies, immature females dispersed farther and were recovered in higher numbers than mature females, regardless of attractant, and recapture of both cohorts was higher with torula yeast. For mature feral flies, range of the synthetic lure was determined to be 30 m. With sterile females, effective range of both attractants was 20 m. Contour maps indicated that wind direction had a strong influence on the active space of attractants, as reflected by distribution of captured flies.

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.

Laboratory and field cage studies on female-targeted attract-and-kill bait stations for Anastrepha suspensa (Diptera: Tephritidae).

BACKGROUND: Development of attract-and-kill bait stations for pest fruit flies has been limited by the water solubility of sugar needed as a feeding stimulant and by the volatility of chemical attractants. A wax-based matrix was developed that provides the longevity needed for field use and is biodegradable. RESULTS: Laboratory bioassays with the Caribbean fruit fly, Anastrepha suspensa (Loew), confirmed the efficacy of bait stations containing avermectin, methomyl, spinosad and phloxine B. Field cage studies demonstrated that significant mortality occurred with either 1% (w/v) spinosad or 1% (w/v) methomyl bait stations versus pesticide-free bait stations. Bait stations were exposed to environmental conditions by placing them in trees at the ARS station in Miami, Florida, between tests. There was no loss in efficacy, in spite of exposure to over 360 mm of rainfall over the 56 days of the study, indicating that the bait stations could provide population suppression for at least 1-2 months when used in subtropical environments. CONCLUSION: A long-lasting, female-targeted fruit fly bait station, such as the one developed herein, could provide a cost-effective option for fruit fly population suppression that would be an important tool in tephritid pest management and control. Additional studies are needed to demonstrate efficacy against wild fruit fly populations and determine deployment strategies.

Dynamics of pH modification of an acidic protein bait used for tropical fruit flies (Diptera: Tephritidae).

Several species of Anastrepha and Bactrocera fruit flies (Diptera: Tephritidae) are captured in traps baited with the protein bait NuLure combined with borax (sodium tetraborate decahydrate) in an aqueous solution, typically 9% NuLure (vol:vol) with 3% borax (wt:vol). NuLure is an acid hydrolysate of corn and has an acidic pH. Addition of borax makes the solution more alkaline, and increase in alkalinity results in increase of ammonia release from the bait solution. This is a very dynamic system, with resultant pH affected by factors such as the amount of borax added, the pH of the water used for preparation, the age of the bait solution, and the development of microbial growth. Problems with borax include amount needed to increase alkalinity of NuLure solutions, which creates difficulties in disposing of spent bait in fruit fly trapping programs. Therefore, research was conducted to evaluate NaOH as an alternative method to increase alkalinity of NuLure solutions. Laboratory experiments compared effect of NaOH versus borax for pH modification on changes in pH and ammonia content of NuLure solutions over time. Although NuLure/NaOH solutions could be adjusted to a more alkaline pH than NuLure/borax solutions, borax plays a critical role in pH stability over time. However, the pH of NuLure/NaOH is stabilized when propylene glycol (10% vol:vol) was used to prepare the bait solution. The use of NaOH can provide an alternative to the use of borax to increase bait solution alkalinity.

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.

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.

Efficacy of 1,4-diaminobutane (putrescine) in a food-based synthetic attractant for capture of Mediterranean and Mexican fruit flies (Diptera: Tephritidae).

Field trials were conducted in Guatemala to evaluate the importance of 1,4 diaminobutane (putrescine) in traps baited with ammonium acetate, trimethylamine, and putrescine. For the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), there were no differences in percentage of females captured in coffee and citrus or in percentage of males captured in citrus in traps with ammonium acetate and trimethylamine lures (females in coffee, 26.4 +/- 6.27%; females in citrus, 35.7 +/- 5.35%; males in citrus, 37.7 +/- 7.48%) versus ammonium acetate, trimethylamine, and putrescine lures (females in coffee, 36.6 +/- 9.64%; females in citrus, 41.1 +/- 5.18%; males in citrus, 37.1 +/- 6.09%). Percentage of males captured in coffee was reduced significantly when putrescine was not used with the ammonium acetate and trimethylamine (39.9 +/- 4.34 versus 31.6 +/- 5.29%). Lower percentages were captured in traps baited with ammonium acetate and putrescine, and the lowest percentages were captured in traps baited with putrescine and trimethylamine. When population level as indicated by capture in traps baited with ammonium acetate, trimethylamine, and putrescine was considered, a higher percentage of C. capitata males were captured in traps baited with all three components when one or more flies per trap per day were captured in coffee, and a higher percentage of females were captured when less than one fly per trap per day was captured in citrus. Percentage of the Mexican fruit fly, Anastrepha ludens (Loew), captured was significantly higher in traps baited with ammonium acetate and putrescine and significantly lower in traps baited putrescine and trimethylamine than in all other treatments. Results indicate that putrescine may be deleted when monitoring established populations of C. capitata but should be used in traps used to monitor A. ludens or to detect new infestations of C. capitata.

Capture of Mediterranean fruit flies (Diptera: Tephritidae) in dry traps baited with a food-based attractant and Jackson traps baited with trimedlure during sterile male release in Guatemala.

Captures of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in Jackson traps baited with trimedlure were compared with captures in cylindrical open-bottom dry traps baited with a food-based synthetic attractant (ammonium acetate, putrescine, and trimethylamine). Tests were conducted in Guatemala during a sterile male release program in an area where wild flies were present in low numbers. More wild and sterile females were captured in food-based traps, and more wild and sterile males were captured in trimedlure traps. The food-based traps captured almost twice as many total (male plus female) wild flies as the trimedlure traps, but the difference was not significant. Females made up approximately 60% of the wild flies caught in the food-based attractant traps; the trimedlure traps caught no females. The ratio of capture of males in trimedlure traps to food-based traps was 6.5:1 for sterile and 1.7:1 for wild flies. Because fewer sterile males are captured in the food-based traps, there is a reduction in the labor-intensive process of examining flies for sterility. The results indicate that traps baited with food-based attractants could be used in place of the Jackson/trimedlure traps for C. capitata sterile release programs because they can monitor distributions of sterile releases and detect wild fly populations effectively; both critical components of fruit fly eradication programs by using the sterile insect technique.