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BACKGROUND: 4-hydroxychlorothalonil (HCT, R182281), a transformation product of the fungicide chlorothalonil, was recently identified in human serum and breast milk. There are indications that HCT may be more toxic and environmentally persistent than chlorothalonil. OBJECTIVE: Our aim was to investigate serum concentrations of HCT in pregnant women in Sweden and Costa Rica. METHODS: We developed a quantitative analytical method for HCT using liquid chromatography tandem mass spectrometry. We measured HCT in 1808 serum samples from pregnant women from the general population in Sweden (1997-2015) and in 632 samples from 393 pregnant women from an agricultural population in Costa Rica (2010-2011). In Swedish samples, we assessed time trends and investigated seasonality. In the Costa Rican samples, we evaluated variability between and within women and explanatory variables of HCT concentrations. RESULTS: HCT was detected in all serum samples, and the limit of detection was 0.1 µg/L. The median HCT concentration in the Swedish samples was 4.1 µg/L (interquartile range [IQR] of 2.9 - 5.8 µg/L), and 3.9 times higher in the Costa Rican samples (median: 16.1 µg/L; IQR: 10.6 - 25.0 µg/L). We found clear seasonal variation with higher concentrations in the first half of each year among Swedish women. In the Costa Rican study, women working in agriculture and living near banana plantations had higher HCT concentrations, whilst higher parity and having a partner working in agriculture were associated with decreased HCT, and no clear seasonal pattern was observed. IMPACT STATEMENT: For the first time, this study quantifies human exposure to the fungicide chlorothalonil and/or its transformation product 4-hydroxychlorothalonil (HCT, R182281) and finds higher serum concentrations in women from a tropical agricultural setting as compared with women from the general population in Sweden.

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Specific mate communication and recognition underlies reproduction and hence speciation. Our study provides new insights in Drosophila melanogaster premating olfactory communication. Mate communication evolves during adaptation to ecological niches and makes use of social signals and habitat cues. Female-produced, species-specific volatile pheromone (Z)-4-undecenal (Z4-11Al) and male pheromone (Z)-11-octadecenyl acetate (cVA) interact with food odour in a sex-specific manner. Furthermore, Z4-11Al, which mediates upwind flight attraction in both sexes, also elicits courtship in experienced males. Two isoforms of the olfactory receptor Or69a are co-expressed in the same olfactory sensory neurons. Z4-11Al is perceived via Or69aB, while the food odorant (R)-linalool is a main ligand for the other variant, Or69aA. However, only Z4-11Al mediates courtship in experienced males, not (R)-linalool. Behavioural discrimination is reflected by calcium imaging of the antennal lobe, showing distinct glomerular activation patterns by these two compounds. Male sex pheromone cVA is known to affect male and female courtship at close range, but does not elicit upwind flight attraction as a single compound, in contrast to Z4-11Al. A blend of the food odour vinegar and cVA attracted females, while a blend of vinegar and female pheromone Z4-11Al attracted males, instead. Sex-specific upwind flight attraction to blends of food volatiles and male and female pheromone, respectively, adds a new element to Drosophila olfactory premating communication and is an unambiguous paradigm for identifying the behaviourally active components, towards a more complete concept of food-pheromone odour objects.

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Specific mate recognition relies on the chemical senses in most animals, and especially in nocturnal insects. Two signal types mediate premating olfactory communication in terrestrial habitats: sex pheromones, which blend into an atmosphere of plant odorants. We show that host plant volatiles affect the perception of sex pheromone in males of the African cotton leafworm Spodoptera littoralis and that pheromone and plant volatiles are not perceived as independent messages. In clean air, S. littoralis males are attracted to single synthetic pheromone components or even the pheromone of a sibling species, oriental cotton leafworm S. litura. Presence of host plant volatiles, however, reduces the male response to deficient or heterospecific pheromone signals. That plant cues enhance discrimination of sex pheromone quality confirms the idea that specific mate recognition in noctuid moths has evolved in concert with adaptation to host plants. Shifts in either female host preference or sex pheromone biosynthesis give rise to new communication channels that have the potential to initiate or contribute to reproductive isolation.

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Guatemalan potato moth, Tecia solanivora, lay eggs in the soil nearby potato Solanum spp. and larvae feed on the tubers. We investigated the oviposition behaviour of T. solanivora females and the survival of larval offspring on healthy vs. stressed, i.e. light exposed and/or damaged potato tubers. In choice tests, females laid significantly more eggs in response to potato odour of healthy tubers and female oviposition preference correlated with higher larval survival. Survival of larvae was negatively correlated with the tuber content of the steroid glycoalkaloids α-solanine and α-chaconine: healthy potatoes contained lower amounts than stressed tubers, ranging from 25 to 500 µg g⁻¹ and from 30 to 600 µg g⁻¹, respectively. Analysis of volatile compounds emitted by potato tubers revealed that stressed tubers could clearly be distinguished from healthy tubers by the composition of their volatile profiles. Compounds that contributed to this difference were e.g. decanal, nonanal, isopropyl myristate, phenylacetaldehyde, benzothiazole, heptadecane, octadecane, myristicin, E,E-α-farnesene and verbenone. Oviposition assays, when female moths were not in contact with the tubers, clearly demonstrated that volatiles guide the females to lay fewer eggs on stressed tubers that are of inferior quality for the larvae. We propose that volatiles, such as sesquiterpenes and aldehydes, mediate oviposition behaviour and are correlated with biosynthetically related, non-volatile compounds, such as steroidal glycoalkaloids, which influence larval survival. We conclude that the oviposition response and larval survival of T. solanivora on healthy vs. stressed tubers supports the preference performance hypothesis for insect herbivores.

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The behavioral mechanisms of mating disruption in Guatemalan potato moth Tecia solanivora were studied using the sex pheromone components, (E)-3-dodecenyl acetate, (Z)-3-dodecenyl acetate, and dodecyl acetate, formulated in a 100:1:20-ratio mimicking the female-produced blend, and in a 100:56:100 off-blend ratio. The mode of action of these two blends was tested in mating disruption experiments in the field and in a greenhouse, as well as in a laboratory wind tunnel. Field treatments with both blends at 80 g pheromone per ha reduced male attraction to trap lures baited with 100 µg of female sex pheromone. In mesh-house treatments, these two blends were equally effective at reducing male attraction to traps baited with live females and mating of caged females. Subsequent flight tunnel tests corroborated that both blends reduced attraction of naive males to calling females, and pre-exposure of males with either dispenser blend for 24 hr resulted in a strongly reduced response to calling females. The pre-exposure effect was reversible, with males again responsive after 24 hr in clean air. The two dispenser formulations produced a similar effect on male behavior, despite the differences in blend composition. One mating disruption dispenser formulated with either the female-blend or off-blend elicited the same rate of male upwind attraction in a wind-tunnel bioassay. Sensory overload and camouflage, therefore, are contributing mechanisms to mating disruption using either blend. The off-blend, which is more economical to synthesize, is a valuable tool for further development of mating disruption against this major pest of potatoes in Latin America.

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The tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae) is a devastating pest of cultivated tomato Solanum lycopersicum throughout South and Central America and Europe. We aimed to characterize the behavioral mechanisms and the chemical cues involved in host selection of T. absoluta females by chemical analysis of tomato leaf volatiles, wind tunnel attraction assays, and oviposition bioassays. Tomato leaf odor elicited in mated females upwind orientation flight followed by landing as well as egg-laying, demonstrating the essential role of plant volatiles in T. absoluta host-finding behavior. In wind tunnel and oviposition choice experiments, T. absoluta females significantly preferred tomato S. lycopersicum over wild tomato Solanum habrochaites, which is resistant to larval feeding. This indicates that leaf volatiles provide information on the suitability of plants as larval hosts. Mated females also discriminated three cultivars of S. lycopersicum according to their volatile profiles. Headspace collections from leaves of these three cultivars contained large amounts of ß-phellandrene, followed by limonene, 2-carene, and (E)-ß-caryophyllene, which together accounted for more than 70% of tomato foliage headspace. Most leaf volatiles were released by all three cultivars, but they showed significant differences with respect to the presence of a few minor compounds and blend proportion. This is an initial study of the volatile signatures that mediate attraction and oviposition of tomato leafminer T. absoluta in response to its main host, tomato.

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The Guatemalan moth Tecia solanivora is an invasive pest of potato in Central and South America. The larvae infest potato tubers in the field as well as in storage facilities. The headspace of potato foliage and potato tubers was studied with regard to volatiles that mediate host-finding and oviposition in the Guatemalan moth. Foliage of three phenological stages, from sprouting to tuberization and flowering, released more than 30 sesquiterpenes. The main compounds were beta-caryophyllene, germacrene-D-4-ol, germacrene-D, kunzeaol, and (E,E)-alpha-farnesene. Sesquiterpenes accounted for >90% of the headspace of green plants, whereas fresh potato tubers emitted only trace amounts of a few sesquiterpenes. Screening of headspace collections with antennae of Guatemalan moth females showed a strong response to several sesquiterpenes and monoterpenes that were emitted from foliage only. In addition, antennae responded to methyl phenylacetate, a floral fragrance that was released in large amounts from flowering plants and that was also present in tuber headspace. Female and male moths were attracted to methyl phenylacetate; this compound may accordingly contribute to female attraction to tuber-bearing potato plants in the field as well as to potato tubers in storage. Oviposition tests showed that females lay eggs near mature flowering plants. Eggs were laid in soil close to the plant and not on potato stems and foliage, which may be due to avoidance of terpenoid compounds released from green plant parts at close range. The results support the concept that potato volatiles mediate host-finding and oviposition behavior and that these compounds may become useful tools for management of the Guatemalan moth.

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