Pheromone–mediated mating disruption in the millet stem borer, \u3ci\u3eConiesta ignefusalis\u3c/i\u3e (Lepidoptera: Pyralidae)

The millet stem borer, Coniesta ignefusalis Hampson (Lepidoptera: Pyralidae), is a major pest of pearl millet in the Sahelian region of Africa. The female sex pheromone has been identified and synthesized, and previous research had shown that the synthetic pheromone could cause high levels of reproductive communication disruption in small plots when released at rates of 640 mg/ha/day, using PVC resin formulation renewed every seven days to maintain efficiency. In the present research, in experiments in farmers’ fields in Niger, 86.8% (SE = 2.6%) communication disruption was achieved when polyethylene vials loaded with 0.5 mg pheromone at 400 dispensers/ha were used and replaced every 21 days. Polyethylene vials loaded with 80 mg pheromone gave uniform, zero–order release at approximately 0.05 mg/day at 27 °C. Experiments carried out on replicated 0.5 ha plots in farmers’ fields in Niger using a single application of these dispensers at 400 dispensers/ha resulted in at least 99% suppression of pheromone trap catches of male C. ignefusalis moths in treated plots relative to numbers in untreated plots for up to 3 months. However, sampling the central portions of these plots before and after harvest showed no significant differences in infestation, damage or yield loss between plots treated with pheromone and untreated plots. This may have been because of small plot size and the immigration of mated female moths into the treated plots which negated any reduction of mating of females within the treated plots. Comparisons of numbers of male C. ignefusalis moths in traps baited with the standard 0.5 mg monitoring lures and those baited with the 80 mg disruption dispensers showed catches in the latter were only 10–20% of those in the former; indicating high level communication disruptions in traps with high dose dispensers. Implications of using insect synthetic pheromones in the development of integrated management of C. ignefusalis in pearl millet cropping systems in the Sahel are discussed

Identification of the aggregation pheromone of the invasive guam strain of coconut rhinoceros beetle, Oryctes rhinoceros, and determination of stereochemistry

The coconut rhinoceros beetle, Oryctes rhinoceros (CRB), is a major pest of coconut and oil palm that has been effectively controlled by the Oryctes rhinoceros nudivirus for over 30 years. A new haplotype, CRB-G, that is not controlled by the virus appeared in Guam in 2007 and has since spread to other countries in the Region. There has been much research on alternative methods to control CRB-G, and there have been reports that it does not respond to the well-established aggregation pheromone of CRB. We found that the male CRB-G beetles produce ethyl 4-methyloctanoate and 4-methyloctanoic acid in 4:1 ratio, essentially as reported for CRB previously by Hallett et al. (1995). The enantiomers of these compounds were synthesised by enzymatic resolution and both the male-produced compounds were shown to be (R)-enantiomers. Hallet et al. (1995) reported that CRB produced the (S)-enantiomers on the basis of field studies, but re-examination of the pheromone produced by CRB beetles confirmed that they also produced the (R)-enantiomers. Electroantennogram (EAG) responses to natural volatile collections from Oryctes and to the synthetic compounds indicated that both male and female beetles respond to the ester but not to the acid. EAG responses were recorded to both enantiomers, but responses to the ethyl (R)-4-methyloctanoate were consistently greater than those to the (S)-enantiomer. In field testing in Papua New Guinea, ethyl (R)-4-methyloctanoate was attractive to both male and female CRB-G beetles and significantly more attractive than the (S)-enantiomer. The racemic ester was as attractive as the (R)-enantiomer, and addition of (R)-4-methyloctanoic acid gave a marginal increase in attractiveness of the lure. Thus CRB-G beetles produce the same pheromone as CRB, although the enantiomeric composition of this was previously wrongly assigned. Both male and female CRB-G are attracted by racemic ethyl 4-methyloctanoate in the field, so that the same lures can be used for monitoring and control of CRB-G as for CRB

Identification of components of the aggregation pheromone of the Guam strain of coconut rhinoceros beetle, Oryctes rhinoceros, and determination of stereochemistry

The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dynastinae) (CRB), is endemic to tropical Asia where it damages both coconut and oil palm. A new invasion by CRB occurred on Guam in 2007 and eradication attempts failed using commonly applied Oryctes rhinoceros nudivirus (OrNV) isolates. This and subsequent invasive outbreaks were found to have been caused by a previously unrecognized haplotype, CRB-G, which appeared to be tolerant to OrNV. The male-produced aggregation pheromone of the endemic, susceptible strain of O. rhinoceros (CRB-S) was previously identified as ethyl 4-methyloctanoate. Following reports from growers that commercial lures containing this compound were not attractive to CRB-G, the aim of this work was to identify the pheromone of CRB-G. Initial collections of volatiles from virgin male and female CRB-G adults from the Solomon Islands failed to show any male- or female-specific compounds as candidate pheromone components. Only after five months were significant quantities of ethyl 4-methyloctanoate and 4-methyloctanoic acid produced by males but not by females. No other male-specific compounds could be detected, in particular methyl 4-methyloctanoate, 4-methyl-1-octanol, or 4-methyl-1-octyl acetate, compounds identified in volatiles from some other species of Oryctes. Ethyl 4-methyloctanoate elicited a strong electroantennogram response from both male and female CRB-G, but these other compounds, including 4-methyloctanoic acid, did not. The enantiomers of ethyl 4-methyloctanoate and 4-methyloctanoic acid were conveniently prepared by enzymatic resolution of the commercially-available acid, and the enantiomers of the acid, but not the ester, could be separated by gas chromatography on an enantioselective cyclodextrin phase. Using this approach, both ethyl 4-methyloctanoate and 4-methyloctanoic acid produced by male CRB-G were shown to be exclusively the (R)-enantiomers whereas previous reports had suggested male O. rhinoceros produced the (S)-enantiomers. However, re-examination of the ester and acid produced by male CRB-S from Papua New Guinea showed that these were also the (R)-enantiomers. In field trapping experiments carried out in the Solomon Islands, both racemic and ethyl (R)-4-methyloctanoate were highly attractive to both male and female CRB-G beetles. The (S)-enantiomer and the corresponding acids were only weakly attractive. The addition of racemic 4-methyloctanoic acid to ethyl 4-methyloctanoate did significantly increase attractiveness, but the addition of (R)- or (S)-4-methyloctanoic acid to the corresponding ethyl esters did not. Possible reasons for the difference in assignment of configuration of the components of the CRB pheromone are discussed along with the practical implications of these results

Floral scent changes in response to pollen removal are rare in buzz-pollinated Solanum

Main conclusion One of seven Solanum taxa studied displayed associations between pollen presence and floral scent composition and volume, suggesting buzz-pollinated plants rarely use scent as an honest cue for foraging pollinators. Abstract Floral scent influences the recruitment, learning, and behaviour of floral visitors. Variation in floral scent can provide information on the amount of reward available or whether a flower has been visited recently and may be particularly important in species with visually concealed rewards. In many buzz-pollinated flowers, tubular anthers opening via small apical pores (poricidal anthers) visually conceal pollen and appear similar regardless of pollen quantity within the anther. We investigated whether pollen removal changes floral scent composition and emission rate in seven taxa of buzz-pollinated Solanum (Solanaceae). We found that pollen removal reduced both the overall emission of floral scent and the emission of specific compounds (linalool and farnesol) in S. lumholtzianum. Our findings suggest that in six out of seven buzz-pollinated taxa studied here, floral scent could not be used as a signal by visitors as it does not contain information on pollen availability

Methyl N,N‐dimethylanthranilate and ethyl propionate: repellents effective against spotted wing drosophila, Drosophila suzukii

BACKGROUND Spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is an economically important pest of soft and stone fruit crops. The aim of this study was to identify repellents, formulated in dispensers, which could protect crops from D. suzukii. Fourteen potential repellents were screened against summer- and winter-morph D. suzukii through electroantennography and behavioural bioassays. Repellents effective in the laboratory were tested in polytunnels to determine their efficacy in reducing catches in fruit-baited traps. Further trials of three potential repellents were conducted to determine the distances over which repellent dispensers could reduce D. suzukii emergence in a strawberry crop. RESULTS All 14 chemicals screened were detected by the antennae of both D. suzukii morphs. Hexyl acetate and geosmin both elicited a significantly greater corrected EAG response in summer morphs than winter morphs. Summer-morph D. suzukii were repelled by butyl acetate, ethyl propionate, methyl N,N-dimethyl anthranilate, geosmin, methyl salicylate, DEET and benzaldehyde at one or more doses test in laboratory bioassays. Winter morphs were repelled by ethyl propionate, methyl anthranilate, methyl N,N-dimethyl anthranilate, DEET, benzaldehyde and butyl anthranilate at one or more of the doses tested in the laboratory. Ethyl propionate, methyl N,N-dimethylanthranilate and benzaldehyde repelled both morphs from fruit-baited traps in polytunnel trapping trials. Ethyl propionate and methyl N,N-dimethylanthranilate reduced emergence of D. suzukii in a strawberry crop over 3–5 m. CONCLUSIONS Ethyl propionate and methyl N,N-dimethylanthranilate may protect strawberry crops against D. suzukii. Future work should test these repellents in combination with attractants in a ‘push-pull’ strategy

Components of the female sex pheromone of the newly-described canola flower midge, Contarinia brassicola

The canola flower midge, Contarinia brassicola Sinclair (Diptera: Cecidomyiidae), is a newly-described species that induces galls on canola, Brassica napus Linnaeus and Brassica rapa Linnaeus (Brassicaceae). Identification of the sex pheromone of C. brassicola is essential to developing monitoring tools to elucidate the geographic range and hosts of this new pest, and the extent to which it threatens the $30 billion Canadian canola industry. The aim of this study was to identify and synthesize the female-produced sex pheromone of C. brassicola and demonstrate its effectiveness in attracting males to traps in the field. Two peaks were identified through GC-EAG analysis of female-produced volatiles which elicited electrophysiological responses in male antennae. These peaks were initially characterized through GC–MS and synthesis as 2,7-diacetoxynonane (major component) and 2-acetoxynonane (minor component), and the racemic compounds elicited EAG responses in male antennae. All four stereoisomers of 2,7-diacetoxynonane were synthesized and the naturally-produced compound was shown to be primarily the (2R,7S)-isomer by analysis on an enantioselective GC column, with a small amount of (2R,7R)-2,7-diacetoxynonane also present. The configuration of the minor component could not be determined because of the small amount present, but this was assumed to be (2R)-2-acetoxynonane by comparison with the configuration of the other two components. In field trials, none of the four stereoisomers of 2,7-diacetoxynonane, presented individually or as a racemic mixture, was attractive to male C. brassicola. However, dispensers loaded with a 10 µg:1 µg blend of (2R,7S)- and (2R,7R)-2,7-diacetoxynonane caught large numbers of male C. brassicola and significantly more than other blends tested. The addition of 0.5 µg of (2R)-2-acetoxynonane to this blend further increased the number of males caught. In future work, we will seek to identify the optimum trapping protocol for the application of the pheromone in monitoring and surveillance

Hero turned villain: Identification of components of the sex pheromone of the tomato bug, Nesidiocoris tenuis

Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae) is a tropical mirid bug used as a biocontrol agent in protected crops, including tomatoes. Although N. tenuis predates important insect pests, especially whitefly, it also causes damage by feeding on tomato plants when prey populations decline, resulting in significant economic losses for growers. The pest is now established in some all-year-round tomato crops in Europe and control measures involve the application of pesticides which are incompatible with current IPM programs. As part of future IPM strategies, the pheromone of N. tenuis was investigated. Volatile collections were made from groups and individuals of mated and unmated, females and males. In analyses of these collections by gas chromatography coupled with electroantennographic (EAG) recording from antennae of male bugs, two EAG-active components were detected and identified as 1-octanol and octyl hexanoate. Unlike other mirids, both male and female N. tenuis produced the two compounds, before and after mating, and both sexes gave EAG responses to both compounds. Furthermore, only octyl hexanoate was detected in whole body solvent washes from both sexes. These compounds are not related to the derivatives of 3-hydroxybutyrate esters found as pheromone components in other members of the Bryocrinae sub-family, and the latter could not be detected in volatiles from N. tenuis and did not elicit EAG responses. Nevertheless, experiments carried out in commercial glasshouses showed that traps baited with a blend of the synthetic pheromone components caught essentially only male N. tenuis, and significantly more than traps baited with octyl hexanoate alone. The latter caught significantly more N. tenuis than unbaited traps which generally caught very few bugs. Traps at plant height caught more N. tenuis males than traps 1 m above or at the base of the plants. The trap catches provided an indication of population levels of N. tenuis and were greatly reduced following an application of insecticide

Mechanisms in mutualisms: a chemically mediated thrips pollination strategy in common elder

The concept of flower-feeding thrips as pollinating insects in temperate regions is rarely considered as thrips are more frequently regarded to be destructive florivores feeding on pollen and surrounding plant tissue. Combining laboratory and field-based studies we examined interactions between Sambucus nigra (elderflower) and Thrips major within their native range to ascertain the role of thrips in the pollination of this species and to determine if floral chemicals mediated flower visits. If thrips provide a pollination service to S. nigra, then this will likely manifest in traits that attract the pollinating taxa at temporally critical points in floral development. T. major were highly abundant in inflorescences of S. nigra, entering flowers when stigmas were pollen-receptive and anthers were immature. When thrips were excluded from the inflorescences fruit-set failed. Linalool was the major component of the inflorescence headspace with peak abundance coinciding with the highest number of adult thrips visiting flowers. Thrips were absent in buds and their numbers declined again in senescing flowers correlating with the concentration of cyanogenic glycosides recorded in the floral tissue. Our data show that S. nigra floral chemistry mediates the behaviour of pollen-feeding thrips by attracting adults in high numbers to the flowers at pre-anthesis stage, while producing deterrent compounds prior to fruit development. Taking an integrative approach to studying thrips behaviour and floral biology we provide a new insight into the previously ambiguously defined pollination strategies of S. nigra and provide evidence that suggests that the relationship between T. major and S. nigra is mutualistic

Chemical variation and insecticidal activity of Lippia javanica (Burm. F.) Spreng essential oil against Sitophilus zeamais Motschulsky

Lippia javanica (Burm. f.) Spreng is used commercially as an herbal tea and medicinal plant in sub-Saharan Africa. Here we investigated the chemical variation and pesticidal potential of L. javanica essential oils against a major stored product pest, Sitophilus zeamais Motschulsky. We identified two morphologically distinct varieties of L. javanica growing at different locations in Malawi. Perillaldehyde was the major constituent in oil of L. javanica var. javanica while myrcenone (ipsdienone) was the major compound in oils of L. javanica var. whytei. Myrcene, linalool, carvone, β-caryophyllene and germacrene D were identified as the other most significant components in oils from both varieties. The yields of oil and the chemical composition also varied significantly with time of harvest during the season in both cases. In contact toxicity tests against S. zeamais, oils from both varieties were active. However, whereas perillaldehyde, linalool and carvone, components of the oil of L. javanica var. javanica, were all toxic against adult S. zeamais, myrcenone, the main component of oil from L. javanica var. whytei, was not. The oil from L. javanica var. javanica also showed some fumigant toxicity against S. zeamais. The high efficacy of L. javanica oil against S. zeamais suggests it is suitable to be used as a botanical insecticide to control S. zeamais in stored maize. However, further research is required to optimise and standardise the variety and harvest time to be recommended and to evaluate its activity against S. zeamais and other storage insect pests under farm conditions before it can be adopted by farmers more widely

Female sex pheromone of the cone moth, dioryctria mendacella: Investigation of synergism between Type I and Type II pheromone components

Polyunsaturated hydrocarbons (Type II pheromone components) have been reported to be synergists for unsaturated acetates, alcohols or aldehydes (Type I components) in the sex pheromones of several species of Lepidoptera. However, there is some debate over whether the active components are the hydrocarbons themselves or more volatile degradation products. Extracts of pheromone glands of adult females of the cone moth, Dioryctria mendacella (Lepidoptera: Pyralidae), contain (Z,E)-9,11-tetradecadienyl acetate (ZE9,11-14:Ac) and at least ten times as much (Z,Z,Z,Z,Z)-3,6,9,12,15-pentacosapentaene (ZZZZZ3,6,9,12,15-25:H). The former elicits a strong electroantennogram response from males while no response could be recorded to the latter. In field trapping tests, both compounds were individually unattractive to male D. mendacella moths, but blends of the two compounds containing at least a 10:1 ratio of ZZZZZ3,6,9,12,15-25:H : ZE9,11-14:Ac were highly attractive. The relatively involatile hydrocarbon was shown to be released from the dispensers used and no significant degradation could be detected. Furthermore, blends of ZE9,11-14:Ac and analogs of ZZZZZ3,6,9,12,15-25:H with fewer carbons and/or double bonds that might be expected to produce similar degradation products to ZZZZZ3,6,9,12,15-25:H were unattractive. This indicated a specific response to the hydrocarbon itself, further substantiated by the observation that related hydrocarbons did not interfere with the activity of ZZZZZ3,6,9,12,15-25:H. Thus a three-step conversion of fish oil was used to produce a blend of unsaturated hydrocarbons containing ZZZZZ3,6,9,12,15-25:H as the major component, albeit only 30% of the total, and a blend of this material with ZE9,11-14:Ac was as attractive to male D. mendacella moths as blends with an equivalent amount of the purified material. This mixture of unsaturated hydrocarbons is much cheaper to produce than the pure pentaene, and may be useful in lures for other species using these compounds. Dioryctria mendacella is a major constraint to production of edible pine kernels throughout the Mediterranean region. Pheromone traps will provide a means to improve monitoring of seasonal flight patterns and changes in population abundance of this pest