E 2 decenal

The study used n-Alkane (C₇-C₃₀) standards and the available authentic standards, including ethyl acetate (≥99.5%), propyl acetate (≥99.5%), butyl acetate (99.7%), ethyl trans-2-butenoate, ethyl hexanoate (≥99%), ethyl heptanoate (≥99%), ethyl octanoate (≥99%), ethyl 3-hydroxybutyrate (≥ 98%), hexyl hexanoate (≥ 98%), hexanal (≥95%), (Z)-3-hexenal (50% in triacetin), (E)-2-hexenal (≥97%), nonanal (≥99.5%), benzaldehyde (≥99.5%), (E)-2-decenal (≥95%), citral (≥95%), 1-butanol (≥99.4%), 1-hexanol (≥99.9%), (E)-2-hexenol (96%), 1-octen-3-ol (≥98%), 1-heptanol (≥99.5%), 2-ethylhexanol (≥99%), 1-octanol (≥99%), 2-octen-1-ol (97%), (Z)-5-octen-1-ol (≥97%), (E)-5-decen-1-ol (≥97%), phenylethyl alcohol (≥99%), cinnamyl alcohol (≥96%), acetic acid (≥99.7%), hexanoic acid (≥98%), heptanoic acid (≥99%), octanoic acid (99%), nonanoic acid (≥99.5%), limonene (mixture of D- and L-form at ratio of 1:1, ≥95%), linalool (≥99%), citronellol (≥95%), nerol (≥97%), geraniol (≥98.5%), 2-octanone (≥99.5%), acetophenone (≥99.5%), 2-pentylfuran (≥97%), 2-octanol (≥97%), and sodium chloride (NaCl, ≥99%) which were all purchased from Sigma-Aldrich (St. Louis, MO, USA). Geranic acid (sum of isomers, 98%) was purchased from Alfa Aesar Corporation (Tianjin, China). Ultrapure water was prepared using a Milli-Q water purification system (Millipore Corporation, Bedford, MA, USA) with a 0.22 μm filter.

Quantitative calibration standards of 2, 10, 20, 100, and 200 ng/μl were made from (E)-2-octenal, (E)-2-decenal, and tridecane (all >94%, Sigma-Aldrich, Australia) diluted using dichloromethane. All calibration standards also contained tetralin (IS) added from a 10 μg/μl stock. (E)-2-octenal, (E)-2-decenal, and tridecane quantities from H. halys headspace samples were calculated using calibration linear equations. 4-Oxo-(E)-2-hexenal was prepared from 2-ethylfuran following Moreira and Millar [18 (link)]. To determine whether differences in defensive compound quantity between diapausing and diapause-disrupted H. halys were significant, non-parametric Mann-Whitney U two-tailed tests were performed, following Shapiro-Wilk tests for normality.

n-Alkanes (C7-C30) for the retention index (RI) calculation, 2-methyl-3-heptanone (99%, internal standard), (E,Z)-2,6-nonadienal (95%), (E)-2-heptenal (97%), decanal (≥98%), octanol (≥99%), (E,Z)-2,6-nonadienol (≥95%), (E)-2-octenal (≥95%), diisopropyl disulfide (≥96%), hexanol (≥99%), (E)-2-nonenal (97%), (E)-2-decenal (≥95%), nonanol (98%), and (E)-2-octenol (97%) were purchased from Sigma-Aldrich (Beijing, China). Hexane, diethyl ether, n-pentane, and anhydrous Na₂SO₄ used for extraction and separation of flavor substances were all analytical reagent and provided by Banxia Scientific Instruments Co. Ltd. (Beijing, China).

The exposure of T. mitsukurii to the synthetic chemical cues of BMSB and N. viridula was carried out considering the naturally released compounds of the two pentatomids [33 (link),36 (link)], using their main components. These components were tridecane, (E)-2-decenal and (E)-2-hexenal (Sigma-Aldrich, Sent Luis, MO, USA). According to Malek et al. (2021) [33 (link)], the 4:1 ratio of tridecane to (E)-2-decenal (1.6: 0.4 nl/mL) has a significant positive effect on the foraging behaviour of T. japonicus. In this study, we used the same ratio for T. mitsukurii in the case of BMSB. As for N. viridula, we used a 3:1 ratio for the two main components of its footprints, tridecane and (E)-2-hexenal (1.5: 0.5 nl/mL), as indicated by the study of Aldrich et al. (1978) [36 (link)]. Pure compounds were prepared using aliquots containing 0.2 nL of each compound in 100 µL of the solvent dichloromethane (Sigma-Aldrich Chemie, Steinheim, Germany). For the control, 100 µL aliquots of the solvent dichloromethane were deployed. The above-mentioned compounds were applied on sterile filter papers (6 cm ø) and left to dry for 2 min. The experimental design remained the same as in footprint trials.

n-Hexane, 0.5 N sodium methoxide, and 14% boron trifluoride–methanol were purchased from Sigma-Aldrich (St. Louis, MO, USA); sodium chloride (NaCl) from Panreac Química SLU (Castellar del Vallès, Spain); and anhydrous sodium sulfate (Na₂SO₄) for gas chromatography (GC) from Scharlau (Sentmenat, Spain). Ultrapure water was obtained using a Milli-Q purification system (Millipore, Bedford, MA, USA).
The tridecanoic acid (C13:0) methyl ester was used as a standard for the analysis of FAs and was acquired from Sigma-Aldrich. The following standards (CAS number and purity percentage in parenthesis) were used for the analysis of VOCs and were purchased from Sigma-Aldrich: (E)-2-decenal (3913-81-3, ≥95.0%), (E)-2-heptenal (18829-55-5, ≥95%), (E)-2-hexenal (6728-26-3, ≥97.0%), (E,E)-2,4-hexadienal (142-83-6, ≥95.0%), (Z)-3-hexenyl acetate (3681-71-8, ≥98.0%), 1-hexanol (111-27-3, ≥99.9%), 1-octen-3-ol (3391-86-4, ≥98.0%), 3-methyl-1- butanol (123-51-3, ≥98.5%), 6-methyl-5-hepten-2-one (110-93-0, ≥97.0%), acetic acid (64-19-7, ≥99.8%), ethanol (64-17-5, ≥99.9%), ethyl acetate (141-78-6, ≥99.8%), ethyl propanoate (105-37-3, ≥99.7%), hexanal (66-25-1, 98%), nonanal (124-19-6, ≥95%), octane (111-65-9, ≥99.7%), pentanoic acid (109-52-4, ≥99.8%), and propanoic acid (79-09-4, ≥99.8%). 4-Methyl-2-pentanol (123-51-3, ≥95%) was used as an internal standard.