Increased Trap Catches Research Articles

Effects of blood-feeding on olfactory sensitivity of the malaria mosquito Anopheles gambiae: Application of mixed linear models to account for repeated measurements

Olfaction plays an important role in the host-seeking behavior of the malaria mosquito Anopheles gambiae. After a complete blood meal, female mosquitoes will not engage in host-seeking behavior until oviposition has occurred. We investigated if peripheral olfactory sensitivity changed after a blood meal by recording electroantennograms (EAGs) of female mosquitoes at three time points (2h, 48h and 72h) to 15 volatile kairomones of either human origin or documented to emanate from oviposition sites. The EAG-sensitivity was compared with that of females of similar age post eclosion. As is common practice in electrophysiological studies, the EAG recordings were obtained by repeated stimulation of the same antennal preparations. We introduce mixed linear modeling as an improved statistical analysis for electrophysiological data. Two hours after blood ingestion, olfactory sensitivity as quantified through EAG-recording increased significantly and selectively, i.e. for seven compounds, compared to unfed females of the same age. Such short-term electrophysiological sensitization in the olfactory system as a result of feeding has not been documented before for insects. Sensitization to six compounds persisted until 48h or 72h post-blood meal at one or more concentrations. Desensitization was observed at 48 and 72hpbm in response to two and three kairomones, respectively. For several compounds, sensitization at the EAG-level corresponded with sensitization found previously in single sensillum studies on olfactory neurons in antennal sensilla trichodea of An. gambiae females. These effects are likely to reflect sensitization to oviposition cues, as eggs have matured 48–72hpbm. Knowledge of changes in olfactory sensitivity to kairomones can be applied to increase trap catches of malaria mosquitoes that have taken a blood meal and need to locate oviposition sites.

An overlooked component: (Z)-9-tetradecenal as a sex pheromone in Helicoverpa armigera

The sex pheromone blend of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a multi-component system, as is that of many other moths, and (Z)-11-hexadecenal 90–99%+(Z)-9-hexadecenal 10–1% was recommended as a standard blend for attracting the species. However, this fails to account for the significance of other compounds that exist in the sex gland. The aim of the present study was to investigate the function of other compounds present in the female sex gland of H. armigera. Extract of female sex glands were analysed by GC–MS combined with GC–EAD. Total 10 compounds were identified, which two novel were reported in female sex gland: heptanal and nonanal, and some previously identified compounds were confirmed. We developed bioassays to evaluate the potential roles of these 10 compounds. In Y-tube bioassays, the gland constituents hexadecanal, (Z)-7-hexadecenal and (Z)-9-tetradecenal increased male attractiveness when added as a three-compound admixture to the standard blend. Field trapping tests showed that (Z)-9-tetradecenal doubled trap catch in comparison with the standard blend, but that the addition of (Z)-7-hexadecenal and hexadecanal did not significantly increase trap catch. These results indicated that while (Z)-7-hexadecenal and hexadecanal function well only at short range, (Z)-9-tetradecenal plays a very important role at both short and long ranges. We suggest that that (Z)-9-tetradecenal as a previously overlooked sex pheromone component of H. armigera, it should be added to sex pheromone lure formulations to improve pheromone trap sensitivity and the efficacy of commercial mating disruption.

Identification of candidate volatiles that affect the behavioural response of the malaria mosquitoAnopheles gambiae sensu strictoto an active kairomone blend: laboratory and semi‐field assays

Anopheles gambiaeGilessensu stricto(Diptera: Culicidae) is the most important vector of human malaria in sub‐Saharan Africa, affecting the lives of millions of people. Existing tools such as insecticide‐treated nets and indoor‐residual sprays are not only effective, but also have limitations as a result of the development of resistance to insecticides and behavioural adaptations in biting time. Therefore, novel mosquito‐control tools are needed. Odour‐releasing traps have a potential for both trapping and surveillance purposes. Based on the outcome ofex vivogene expression assays andin vivoelectrophysiological assays on hundreds of volatile organic compounds, 29 ‘candidate behaviourally‐disruptive organic compounds' (cBDOCs) are selected, belonging to 10 chemical categories, to be assayed in the laboratory using dual‐choice olfactometers for the ability to modify the ‘attractiveness’ (i.e. significantly more insects being caught in the associated trap) of a basic volatile blend consisting of ammonia, lactic acid and tetradecanoic acid but without additional carbon dioxide. Compounds that either reduce or increase trap catches by the basic blend in the olfactometer experiments are tested under African conditions in choice experiments in a semi‐field facility in Kenya. The release rates of cBDOCs are determined gravimetrically to allow the calculation of aerial concentrations at the trap outlet. Aerial concentrations in the sub‐p.p.m. range are reported for the first time to influence mosquito behaviour. The results of the olfactometer and semi‐field assays generally correspond. Under semi‐field conditions, three compounds, 3‐heptanol (0.025 p.p.m.), 2‐methylpropanal (0.05 p.p.m.) and 4,5‐dimethylthiazole (0.73 p.p.m.), significantly increase trap catches relative to the basic blend consisting of ammonia, lactic acid, tetradecanoic acid and carbon dioxide. 2‐Acetylthiophene, 2‐nonanone and 2‐phenylethanol decrease the number of mosquitoes caught at all concentrations tested under semi‐field conditions. These compounds hold promise as attractants and spatial repellents to be applied in mosquito control programmes.

Interactions among Carbon Dioxide, Heat, and Chemical Lures in Attracting the Bed Bug,Cimex lectulariusL. (Hemiptera: Cimicidae)

Commercial bed bug (Cimex lectulariusL.) monitors incorporating carbon dioxide (CO2), heat, and chemical lures are being used for detecting bed bugs; however, there are few reported studies on the effectiveness of chemical lures in bed bug monitors and the interactions among chemical lure, CO2, and heat. We screened 12 chemicals for their attraction to bed bugs and evaluated interactions among chemical lures, CO2, and heat. The chemical lure mixture consisting of nonanal, 1-octen-3-ol, spearmint oil, and coriander Egyptian oil was found to be most attractive to bed bugs and significantly increased the trap catches in laboratory bioassays. Adding this chemical lure mixture when CO2was present increased the trap catches compared with traps baited with CO2alone, whereas adding heat did not significantly increase trap catches when CO2was present. Results suggest a combination of chemical lure and CO2is essential for designing effective bed bug monitors.

Evaluation of ammonia, human sweat, and bovine blood as attractants for the female canyon fly, Fannia conspicua (Diptera: Muscidae), in southern California

Human sweat, liquid ammonia, and bovine blood are known to be attractive to some hematophagous flies. These materials were evaluated with and without carbon dioxide (CO(2)) for their ability to increase capture of female "canyon flies" (Fannia conspicua Malloch) using CDC-type suction traps (without light). Ammonia acted synergistically with CO(2) to increase trap catch 89.9% over CO(2) alone. There was no synergistic effect of human sweat or bovine blood with CO(2). In the absence of CO(2), none of the three materials increased trap catch of female canyon flies relative to non-baited traps. Implications for canyon fly control and further trap improvement are discussed.

Sugar-fermenting yeast as an organic source of carbon dioxide to attract the malaria mosquito Anopheles gambiae

BackgroundCarbon dioxide (CO2) plays an important role in the host-seeking process of opportunistic, zoophilic and anthropophilic mosquito species and is, therefore, commonly added to mosquito sampling tools. The African malaria vector Anopheles gambiae sensu stricto is attracted to human volatiles augmented by CO2. This study investigated whether CO2, usually supplied from gas cylinders acquired from commercial industry, could be replaced by CO2 derived from fermenting yeast (yeast-produced CO2).MethodsTrapping experiments were conducted in the laboratory, semi-field and field, with An. gambiae s.s. as the target species. MM-X traps were baited with volatiles produced by mixtures of yeast, sugar and water, prepared in 1.5, 5 or 25 L bottles. Catches were compared with traps baited with industrial CO2. The additional effect of human odours was also examined. In the laboratory and semi-field facility dual-choice experiments were conducted. The effect of traps baited with yeast-produced CO2 on the number of mosquitoes entering an African house was studied in the MalariaSphere. Carbon dioxide baited traps, placed outside human dwellings, were also tested in an African village setting. The laboratory and semi-field data were analysed by a χ2-test, the field data by GLM. In addition, CO2 concentrations produced by yeast-sugar solutions were measured over time.ResultsTraps baited with yeast-produced CO2 caught significantly more mosquitoes than unbaited traps (up to 34 h post mixing the ingredients) and also significantly more than traps baited with industrial CO2, both in the laboratory and semi-field. Adding yeast-produced CO2 to traps baited with human odour significantly increased trap catches. In the MalariaSphere, outdoor traps baited with yeast-produced or industrial CO2 + human odour reduced house entry of mosquitoes with a human host sleeping under a bed net indoors. Anopheles gambiae s.s. was not caught during the field trials. However, traps baited with yeast-produced CO2 caught similar numbers of Anopheles arabiensis as traps baited with industrial CO2. Addition of human odour increased trap catches.ConclusionsYeast-produced CO2 can effectively replace industrial CO2 for sampling of An. gambiae s.s.. This will significantly reduce costs and allow sustainable mass-application of odour-baited devices for mosquito sampling in remote areas.

Evaluating the Use of Male-Produced Pheromone Components and Plant Volatiles in Two Trap Designs to MonitorAnoplophora glabripennis

Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), commonly known as the Asian longhorned beetle, is a wood-boring invasive species introduced from Asia to North America and Europe in solid wood packing material. Efficient monitoring traps are needed to assess population density and dispersal in the field and to detect new introductions at ports of entry. For this purpose, we conducted field trapping experiments in China in the summers of 2007 and 2008. In 2007, we tested Intercept panel traps hung on poplar trees. In 2008, we used Intercept panel traps hung on poplar trees, screen sleeve traps wrapped around poplar trunks, and Intercept panel traps hung on bamboo poles 20 m away from host trees. Traps were baited with A. glabripennis male-produced pheromone alone or in different combinations with plant volatiles. Traps baited with the male-produced pheromone alone caught significantly more females than control traps in both years. The addition of a mixture of (-)-linalool, (Z)-3-hexen-1-ol, linalool oxide, trans-caryophyllene, and trans-pinocarveol to the pheromone significantly increased trap catches of females, 85% of which were virgin. Screen sleeve traps baited with a combination of (-)-linalool and the pheromone caught the highest number of beetles overall in 2008, whereas traps placed on bamboo polls caught the lowest number. Although the logistics for the most effective implementation of a trapping program using a mixture of the pheromone and plant volatiles require additional studies, these results indicate that this pheromone has considerable promise as a monitoring tool for A. glabripennis in the field.

Identification, Synthesis and Field Testing of (3Z,6Z,9Z)-3,6,9-Henicosatriene, a Second Bioactive Component of the Sex Pheromone of the Autumn Gum Moth, Mnesampela privata

The sex pheromone of Mnesampela privata, an endemic pest of Eucalyptus plantations in Australia, was previously identified as a single bioactive compound, (3Z,6Z,9Z)-3,6,9-nonadecatriene (C19 triene). Initial field testing of lures containing 1 mg, 5 mg or 10 mg of C19 triene (>98% purity) caught no or very few male M. privata. (3Z,6Z,9Z)-3,6,9-Henicosatriene (C21 triene) was identified as an additional minor pheromone component in abdominal tip extracts of M. privata females from Tasmania. Levels of both compounds extracted from individual females varied greatly, but the ratio was relatively constant at 33:1 C19:C21 trienes. Electroantennograms (EAG) of synthetic C21 triene with male M. privata gave positive but consistently lower responses than elicited by the C19 triene. Field tests showed that the addition of 1-6% C21 triene to 1 mg C19 triene significantly increased trap catch and the detection of M. privata in plantations. Traps baited with a 16:1 ratio caught significantly more moths than those baited with a ratio approximating that of females.

Identification and Field Bioassays of the Sex Pheromone of Synanthedon haitangvora

Two major components from pheromone gland extracts of Synanthedon haitangvora females were identified as (Z,Z)-3,13-octadecadienyl acetate (Z3,Z13-18:OAc) and (E,Z)-2,13-octadecadienyl acetate (E2,Z13-18:OAc), and the average ratio of these components was about 1:1. Seven minor components, (Z)-9-hexadecenyl acetate (Z9-16:OAc), (Z)-11-hexadecenyl acetate (Z11-16:OAc), (Z)-9-octadecenyl acetate (Z9-18:OAc), (Z)-13-octadecenyl acetate (Z13-18:OAc), (E,Z)-3,13-octadecadienyl acetate (E3,Z13-18:OAc), (Z,Z)-3,13-octadecadien-1-ol (Z3,Z13-18:OH), and (E,Z)-2,13-octadecadien-1-ol (E2,Z13-18:OH), also were identified from gland extracts. Field tests showed that male S. haitangvora were attracted to Z3,Z13-18:OAc alone, but the maximum number of males was attracted to the binary blend of Z3,Z13-18:OAc and E2,Z13-18:OAc mimicking the blend found in female extracts. The addition of minor components to a 1:1 blend of Z3,Z13-18:OAc and E2,Z13-18:OAc did not increase the numbers of moths captured. The only significant effect of minor components was the strong inhibitory effect of adding Z3,Z13-18:OH to the primary binary blend. Increasing doses of the optimum pheromone blend in the lures from 0.1 to 2.0 mg increased trap catches of male S. haitangvora.

Electrophysiological and Behavioral Responses ofDendroctonus valens(Coleoptera: Curculionidae: Scolytinae) to Four Bark Beetle Pheromones

The red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Curculionidae: Scolytinae), has caused extensive mortality of Pinus tabuliformis Carrière in north central China. The electrophysiological and behavioral activities of the four bark beetle pheromones, frontalin, exo-brevicomin, trans-verbenol, and cis-verbenol, singly or in combination with host-produced kairomones, were tested on red turpentine beetles. Both sexes showed a consistent electrophysiological response to the four test compounds. In Y-tube olfactometer bioassays, walking red turpentine beetles selected the host compound (+)-3-carene over any of the test compounds, but significantly higher numbers chose each tested pheromone over a blank control. The four compounds, tested singly or in combination, were not attractive to red turpentine beetles in field trapping studies in 2006 and 2007 and also did not significantly increase trap catch when combined with (+)-3-carene. Frontalin, alone or in combination with exo-brevicomin and trans-verbenol, significantly reduced the attractiveness of (+)-3-carene in 2006 but not in 2007. The possible roles of the pheromones in host and mate finding and selection are discussed.

Major Sex Pheromone Components of the Australian Gum Leaf Skeletonizer Uraba lugens: (10E,12Z)-Hexadecadien-1-yl Acetate and (10E,12Z)-Hexadecadien-1-ol

Two sex pheromone components of the gum leaf skeletonizer, Uraba lugens (Lepidoptera: Nolidae), recently established in New Zealand, were identified. Gas chromatography (GC) electroantennographic detection analyses of female pheromone gland extracts gave three compounds that consistently elicited antennal responses. Chemical analyses, using GC and GC-mass spectrometry, in conjunction with 4-methyl-1,2,4-triazoline-3,5-dione and dimethyldisulfide derivatizations, identified these compounds as (10E,12Z)-hexadecadien-1-yl acetate (E10,Z12-16:Ac), (10E,12Z)-hexadecadien-1-ol (E10,Z12-16:OH), and (Z)-11-hexadecen-1-yl acetate (Z11-16:Ac). A trapping trial in Queensland, Australia, in 2002, indicated that a blend of the two major components E10,Z12-16:Ac and E10,Z12-16:OH could attract gum leaf skeletonizer males. In the same trial, E10,Z12-16:Ac alone trapped large numbers of an unidentified nolid, Nola spp. Further trials in Auckland, New Zealand established that these two components were sufficient and necessary for trap catch of males; adding minor gland components, (10E,12E)-hexadecadien-1-yl acetate (E10,E12-16:Ac), Z11-16:Ac, or octadecan-1-ol (18:OH), to the two-component lure did not result in increased trap catches. Behavioral observations and gland analyses of the Auckland population revealed that female moths begin calling soon after emergence, with peak calling and pheromone production occurring 7 hr into the scotophase. Analysis of gland extract at two-hourly intervals during the first activity period showed that the ratio of E10,Z12-16:Ac to E10,Z12-16:OH (mean of 86: 14, respectively) and pheromone titer were fairly constant. No qualitative or quantitative differences in pheromone components were detected between gland extracts from Tasmanian univoltine and Auckland bivoltine populations of U. lugens.

Sources of Insect and Plant Volatiles Attractive to Cottonwood Leaf Beetles Feeding on Hybrid Poplar

The cottonwood leaf beetle, Chrysomela scripta, is the most damaging insect affecting the production of Populus, an important source of sustainable forest products and biomass. Currently, there is no simple method for monitoring C. scripta populations, and nothing is known about potential chemical attractants for trapping. We conducted laboratory assays on sources of attraction to C. scripta adults. In olfactometer trials, beetles were attracted to volatiles released from conspecifics feeding on foliage. There was also significant, but lesser, attraction to odor from unwounded foliage, C. scripta alone, and frass. The latter two results indicate the presence of a pheromone. Wounding of foliage by C. scripta, but not by artificial means, enhanced its attractiveness compared to unwounded foliage, even when C. scripta by-products were removed. In direct comparisons, responses to odor from beetle-wounded foliage were not different from responses to odor from beetles feeding on foliage. We tested the attractiveness of volatiles emitted by adults feeding on foliage in the field using modified boll weevil traps. Results confirm that these volatiles are sufficient to increase trap catches in the field. Color is also important, with yellow baited traps catching more beetles than black baited. We propose that original landing by C. scripta is mediated by host odors and visual cues and that subsequent aggregation is enhanced by chemical cues associated with feeding by conspecifics. This may partially explain clustering in the field and likewise be incorporated into sampling schemes needed for integrated pest management.

FIELD EVALUATION OF A SYNTHETIC FEMALE SEX PHEROMONE FOR THE LEAFMINING MOTH PHYLLOCNISTIS CITRELLA (LEPIDOPTERA: GRACILLARIIDAE) IN FLORIDA CITRUS

Traps baited with a binary mixture in the ratio of 30:10 of two EAG-active compounds, (Z,Z,E)-7,11,13-hexadecatrienal and (Z,Z)-7,11-hexadecadienal, attracted significantly more moths of the leafmining moth, Phyllocnistis citrella, compared with unbaited traps in a Florida citrus grove. The addition of a third EAG-active compound (Z)-7-hexadecenal, did not increase trap catch. Trap height, at 0.7, 1.3 and 2 m, did not significantly affect daily trap catch on 5 of 6 days. Mention of a trade mark or proprietary product does not constitute a guarantee or warranty of the product by the US Department of Agriculture and does not imply its approval to the exclusion of other products that also may be suitable.

Capture of Female Hylotrupes bajulus as Influenced by Trap Type and Pheromone Blend

Three different types of traps were evaluated for a semiochemical-based trapping method for Hylotrupes bajulus (L.) (Cerambycidae). One, designated the ground trap, was the most efficient under both laboratory and natural conditions and had an active space of about 3.5 m. Significantly more beetles were captured in traps baited with a mixture of synthetic pheromones, (3R)-3-hydroxy-2-hexanone [(3R)-ketol] + 1-butanol, than in those with either single compound or with racemic mixtures. Furthermore, the synthetic lure captured more females than two virgin males in a laboratory bioassay. In addition, doubling the concentration of the synthetic pheromone significantly increased trap catches. The present findings have potential value of the management of this pest.

Meteorological effects on adult mosquito (Culex) populations in metropolitan New Jersey

For two metropolitan New Jersey counties, monthly average adult mosquito (Culex) catch from New Jersey light trap data sets covering multiple decades is related to a number of meteorological factors. From June through August climatological conditions accounted for between 40% and 50% of the variation in average catch. In general, high monthly precipitation totals both in the month corresponding to the catch and the previous month were associated with increased trap catch. However, individual heavy rainfall events tended to reduce catch. Warm temperatures exerted a positive influence on mosquito abundance in June, but were associated with a low catch in August. Linear meteorological relationships explained only a small percentage of the variations in mosquito catch during May and September. During July, and particularly August, antecedent monthly catch also explained a significant portion of the variance in the contemporaneous catch. Over 60% of the variability in August catch could be attributed to the July population.

Field Response of Dendroctonus valens (Coleoptera: Scolytidae) and a Major Predator, Temnochila chlorodia (Coleoptera: Trogositidae), to Host Kairomones and a Dendroctonus spp. Pheromone Component1

The red turpentine beetle, Dendroctonus valens (LeConte) (Coleoptera: Scolytidae), is a common bark beetle species found throughout much of North America. Aggregation pheromones have yet to be isolated and identified for D. valens. In this study, we examined the response of D. valens and a bark beetle predator, Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae), to host produced kairomones and to the Dendroctonus spp. pheromone component exo-brevicomin. A total of 11,604 D. valens and 586 T. chlorodia were captured in multiple-funnel traps over a 14-wk period from 27 March to 5 July 2002. There was no significant difference in trap catch related to gender. The ratio of males to females was 1.01 for D. valens and 0.97 for T. chlorodia. Dendroctonus valens showed significant attraction to (+)-α-pinene, (−)-β-pinene, and (+)-3-carene, but the addition of ethanol did not significantly increase trap catch. Racemic exo-brevicomin was not attractive to D. valens and significantly reduced its attraction to the monoterpene and ethanol blend. This observation, in combination with results from other authors, suggests that D. valens is not responding to the western pine beetle, D. brevicomis LeConte, pheromone or any of the individual components. Potential explanations for why D. valens is attracted to D. brevicomis infested trees are provided. There were no significant differences in the trap catch of T. chlorodia among unbaited traps or traps baited with (+)-α-pinene, (−)-β-pinene, and (+)-3-carene or (+)-α-pinene, (−)-(β-pinene, and (+)-3-carene, and ethanol. The addition of exo-brevicomin significantly increased attraction. During the course of this study, a single peak in flight activity was observed during late May through early June for both species.

Insect Trap Catch Improvement with Light-Emitting Diode Modification

Insect traps are vital component of many entomological programs for detection and monitoring of insect populations. We equipped yellow (YC), blue (BC) sticky card (BC) with 530 nm lime green (LED-YC) and 470 nm blue (LED-BC) light-emitting diodes, respectively that increased trap catches of several insect pests. The LED-YC traps caught 1.3, 1.4, 1.8, and 4.8 times more adult greenhouse whitefly Trialeurodes vaporariorum (Westwood), sweetpotato whitefly Bemisia tabaci (Gennadius) biotype B, cotton aphids Gossypium hirsutum (L.), and fungus gnats Bradysia coprophila (Lintner), respectively, compared with standard YC traps. The LED-YC traps did not catch more Eretmocerus spp. than the standard YC traps. Eretmocerus spp. are important B. tabaci parasitoids used in greenhouse biological control programs. For whitefly control in greenhouse the 530 nm lime green LED equipped plastic cup trap designed by Chu et al. (2003) is the better choice than LED-YC trap because it catches few Eretmocerus spp. and Encarsia spp. whitefly parasitoids released for B. tabaci nymph control. The LED-BC traps caught 2.0-2.5 times more adult western flower thrips Franklinella occidentalis (Pergande) compared with the standard BC traps.

Red Turpentine Beetle, <I>Dendroctonus valens</I> LeConte (Coleoptera: Scolytidae), Response to Host Semiochemicals in China

The response of the introduced red turpentine beetle, Dendroctonus valens LeConte, to host semiochemicals in Shanxi Province, China, was distinctly different from that reported in previous studies conducted in the western part of the native range of D. valens in the central Sierra Nevada, CA. This finding suggests either that there is regional variation in D. valens response to host volatiles in North America or that the species underwent rapid adaptation after its introduction into Asia. In the Chinese population of D. valens, (+)-3-carene was the most attractive host monoterpene tested in studies conducted in 2002 using multiple funnel traps suspended in a Pinus tabuliformis stand. It attracted significantly more beetles than did any other single semiochemical or any of the ternary or quaternary blends tested, including the standard D. valens blend used in North America [a 1:1:1 blend of (+)-β-pinene, (−)-&bgr;-pinene, and (+)-3-carene]. (+)-β-Pinene and (−)-&bgr;-pinene, presented individually, were not significantly more attractive than controls. Adding limonene to the standard lure decreased response of D. valens but not significantly. A new type of semiochemical release vial was tested using a range of release rates of a 1:1:1 blend of (+)-β-pinene, (−)-&bgr;-pinene, and (+)-3-carene. The rates ranged from 150 to 210 mg/d, and these were compared with the standard North American lure, which releases ≈110 mg/d. The most attractive of these vials, which released ≈150 mg/d, captured significantly more beetles than did the standard release device; however, increasing the release rate beyond 150 mg/d did not further increase trap catch. The implications of our results for the phylogenetic geography of D. valens and its management as an invasive species are discussed.

Developing pheromone traps and lures for Maruca vitrata in Benin, West Africa

AbstractIn previous work successful trapping of the legume podborer, Maruca vitrata Fabricius (Lepidoptera: Pyralidae), was accomplished using a synthetic pheromone blend consisting of (E,E)‐10,12‐hexadecadienal, (E,E)‐10,12‐hexadecadienol, and (E)‐10‐hexadecenal in a 100 : 5 : 5 ratio. In the present work, experiments were conducted in cowpea fields in Benin to compare different trap designs, and other aspects of the lures. A water‐trap made from a plastic jerry‐can was found to be superior to commercial funnel‐ and sticky‐trap designs, and 120 cm was the optimum height for captures. Generally, lures consisted of polyethylene vials containing 0.1 mg of pheromone. Results showed that shielding the lures from the adverse effects of sunlight with aluminium foil did not increase trap catches of M. vitrata. The degree of isomeric purity of the (E,E)‐10,12‐hexadecadienal and (E,E)‐10,12‐hexadecadienol blend components, in the range 73–99%, had no significant effect on captures, while lures of 80% isomeric purity showed no loss of effectiveness for up to 4 weeks. Similar results were observed with lures from a commercial source containing 0.46 mg of pheromone in the blend ratio 100 : 11 : 6 and 95% isomeric purity. Residue analysis showed that vial lures exposed for 2 weeks in the field still contained 73% of the initial amount of (E,E)‐10,12‐hexadecadienal, compared to rubber septa dispensers, which only retained 22%. Females comprised 11–50% of total catches, confirming earlier, unexpected results for synthetic lures. The observations that effective traps can be made from locally available plastic containers, and that pheromone blend composition and purity are not critical, should reduce costs and improve the feasibility of traps as practical monitoring tools for M. vitrata.

Female sex pheromone of brinjal fruit and shoot borer, Leucinodes orbonalis (Lepidoptera: Pyralidae): trap optimization and application in IPM trials.

Delta and wing traps baited with synthetic female sex pheromone of Leucinodes orbonalis Guenée were found to catch and retain ten times more moths than either Spodoptera or uni-trap designs. Locally-produced water and funnel traps were as effective as delta traps, although 'windows' cut in the side panels of delta traps significantly increased trap catch from 0.4 to 2.3 moths per trap per night. Trap catch was found to be proportional to the radius of sticky disc traps in the range 5-20 cm radius, discs with a 2.5 cm radius caught no moths. Wing traps placed at crop height caught significantly more moths than traps placed 0.5 m above or below the crop canopy. Replicated integrated pest management (IPM) trials (3 x 0.5 ha per treatment) were conducted in farmers fields with young and mature eggplant crops. Farmers applied insecticides at least three times a week in all check and IPM plots. In addition pheromone traps were placed out at a density of 100 per ha and infested shoots removed weekly in the 0.5 ha IPM plots. Pheromone trap catches were reduced significantly from 2.0 to 0.4 moths per trap per night respectively in check and IPM plots in a young crop and 1.1 to 0.3 moths per trap per night in check and IPM plots respectively in a mature crop. Fruit damage was significantly reduced from an average of 41.8% and 51.2% in check plots of young and mature crops respectively to 22% and 26.4 respectively in the associated IPM plots. Significant differences in pheromone trap catches and fruit damage were attained four and two weeks respectively after IPM treatments began in the mature crop whereas in the immature crop significant differences were not observed for the first eight to nine weeks respectively. The relative impact of removing infested shoots and mass trapping on L. orbonalis larval populations was not established in these trials but in both cases there was an estimated increase of approximately 50% in marketable fruit obtained by the combination of control techniques compared to insecticide treatment alone.