The problems of the environment and human health related to the use of synthetic and broad-spectrum insecticides have increasingly motivated scientific research on different alternatives and among these, the use of green systems, such as essential oils, have been explored. Several species of the Apiaceae and Asteraceae families, aromatic herbs rich in secondary bioactive metabolites, are used in the industrial field for pharmaceutical, cosmetic, and food purposes. Different essential oils extracted from some species of these families have shown acute toxicity and attractive and/or repellent effects towards different insects. In our work, we investigated the toxic potential of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum essential oils against four insect species, Sitophilus oryzae, Lasioderma serricorne, Necrobia rufipes, and Rhyzoperta dominica, which are common pests of stored products. The composition of both oils, extracted by hydrodistillation from the aerial parts of the two plants, was evaluated by GC×GC-MS. Calendula incana subsp. maritima essential oil was rich in oxygenated sesquiterpenoids, such as cubebol (35.39%), 4-epi-cubebol (22.99%), and cubenol (12.77%), while the Laserpitium siler subsp. siculum essential oil was composed mainly of monoterpene hydrocarbons, such as β-phellandrene (42.16%), limonene (23.87%), and β-terpinene (11.80%). The toxicity Petri dish bioassays indicated that C. maritima oil killed a mean of 65.50% of S. oryzae and 44.00% of R. dominica adults, indicating a higher biocidal activity in comparison with L. siculum oil, while toward the other species, no significant differences in mortality were recorded. Calendula maritima oil could be, then, considered a promising candidate for further tests as an alternative biocide toward S. oryzae and R. dominica. The possibility that the relatively high content of oxygenated sesquiterpenoids in C. maritima essential oil determines its higher biocidal activity is discussed.

The cigarette beetle, Lasioderma serricorne F. (Coleoptera: Anobiidae) is an important food storage pest affecting the tobacco industry and is increasingly impacting museums and herbaria. Monitoring methods make use of pheromone traps which can be implemented using chili fruit powder. The objective of this study was to assess the response of L. serricorne to the volatile organic compounds (VOCs) from different chili powders in order to identify the main semiochemicals involved in this attraction. Volatiles emitted by Capsicum annuum, C. frutescens, and C. chinense dried fruit powders were tested in an olfactometer and collected and analyzed using SPME and GC-MS. Results indicated that C. annuum and C. frutescens VOCs elicit attraction toward L. serricorne adults in olfactometer, while C. chinense VOCs elicit no attraction. Chemicals analysis showed a higher presence of polar compounds in the VOCs of C. annuum and C. frutescens compared to C. chinense, with α-ionone and β-ionone being more abundant in the attractive species. Further olfactometer bioassays indicated that both α-ionone and β-ionone elicit attraction, suggesting that these compounds are candidates as synergistic attractants in pheromone monitoring traps for L. serricorne.

Key message: This study revealed differing behavioral and antennal responses between large and small female Ips typographus to two bioactive oxygenated monoterpenoids, ( +)-isopinocamphone and 1,8-cineole, which serve contrasting ecological roles as aggregation pheromone synergist and inhibitor. Larger females were more attracted to ( +)-isopinocamphone and had larger antennal clubs leading to enhanced antennal sensitivity, potentially improving their ability to select suitable host trees. In contrast, smaller females were less repelled by 1,8-cineole but had higher antennal sensitivity despite smaller antennae. This discrepancy can be explained by behavioral decisions made after downstream olfactory signal processing in the central nervous system (CNS) and by the co-localization of 1,8-cineole with pheromone-sensitive neurons. Ecologically, small females may avoid competition with larger females by selecting less suitable trees. In conclusion, females’ body size influences olfactory-driven responseto potential host selection decisive volatiles, which can impact reproductive success and bark beetle population dynamics. Context: Ips typographus, a major pest of Norway spruce (Picea abies L.) in Europe, is experiencing more frequent outbreaks due to climate change. These outbreaks involve shifts in population dynamics and phenotypic traits, influencing beetle responses to olfactory cues from stressed host trees. Aims: The study examines the size-dependent behavioral and antennal responses of female I. typographus to two host selection–deciding volatiles with contrasting ecological roles: 1,8-cineole, which inhibits attraction to unsuitable trees, and ( +)-isopinocamphone, a pheromone synergist. Size-linked morphological and olfactory adaptations may influence females’ ability to select suitable host trees for reproduction. Methods: In field trap experiments conducted in 2019 and 2022, the body size of I. typographus females caught in response to different doses of ( +)-isopinocamphone or 1,8-cineole in combination with pheromone was compared. Female Ips typographus were sorted based on body length. In females from the laboratory, the size of the antennal club was measured, and size-dependent antennal responses to these volatiles were analyzed using electroantennography. Results: Larger females were more attracted to ( +)-isopinocamphone in combination with pheromone in the field, showed stronger antennal response, and had larger antennal clubs than smaller females proportionally to their body size. In contrast, smaller females were less repelled by 1,8-cineole added to pheromone, but, in contradiction, antennally responded to it more strongly than larger females despite having smaller antennal clubs. Conclusion: Body length significantly influenced semiochemical detection in I. typographus females. ( +)-Isopinocamphone was detected more effectively by larger females, implying an advantage in the selection of suitable host trees. In contrast, the discrepancy between behavioral and antennal responses to 1,8-cineole in smaller females suggests involvement of not only peripheral responses but also central nervous processing of olfactory signals that influence behavior. This adaptation may enable smaller females to reduce competition with large ones by selecting less suitable trees. These findings provide new insights into the ecological relationship between beetle phenotype and olfactory cues, with implications for tree–bark beetle interactions.

Context: Ips typographus , a major pest of Norway spruce ( Picea abies ) in Europe, is experiencing more frequent outbreaks due to climate change. These outbreaks involve shifts in population dynamics and phenotypic traits, influencing beetle responses to olfactory cues from stressed host trees. Aims: The study examines the size-dependent behavioral and antennal responses of female I. typographus to two host selection–deciding volatiles with contrasting ecological roles: 1,8-cineole, which inhibits attraction to unsuitable trees, and (+)-isopinocamphone, a pheromone synergist. Size-linked morphological and olfactory adaptations may influence females’ ability to select suitable host trees for reproduction. Methods: In field trap experiments conducted in 2019 and 2022, the body size of I. typographus females caught in response to different doses of (+)-isopinocamphone or 1,8-cineole in combination with pheromone was compared. Female Ips typographus were sorted based on body length, the size of the antennal club was measured, and size-dependent antennal responses to these volatiles were analyzed using electroantennography. Results: Larger females were more attracted to (+)-isopinocamphone in combination with pheromone in the field, showed stronger antennal detection, and had proportionally larger antennal clubs than smaller females. In contrast, smaller females were less repelled by 1,8-cineole added to pheromone but, in contradiction, antennally detected it more strongly than larger females despite having smaller antennal clubs. Conclusion: The total body length significantly influences semiochemical detection in I. typographus females. (+)-isopinocamphone was detected more effectively by larger females, implying an advantage in the selection of suitable host trees. In contrast, the discrepancy between behavioral and antennal responses to 1,8-cineole in smaller females suggests the involvement of not only peripheral detection but also central nervous processing of olfactory signals driving behavior. This adaptation may enable smaller females to reduce competition with large ones by selecting less suitable trees. These findings provide new insights into the ecological relationship between beetle morphology and olfactory cues, with implications for tree–bark beetle interactions. Key message: This study revealed differing behavioral and antennal responses between large and small female I. typographus to two bioactive oxygenated monoterpenes, (+)-isopinocamphone and 1,8-cineole, which serve contrasting ecological roles as aggregation pheromone synergist and inhibitor. Larger females were more attracted to (+)-isopinocamphone and had larger antennal clubs leading to enhanced antennal sensitivity, potentially improving their ability to select suitable host trees. In contrast, smaller females were less repelled by 1,8-cineole but had higher antennal sensitivity despite having smaller antennae. This discrepancy can be explained by behavioral decisions made after downstream olfactory signal processing in the central nervous system (CNS) and by the co-localization of 1,8-cineole with pheromone-sensitive neurons. Ecologically, small females may avoid competition with larger females by selecting less suitable trees. In conclusion, females’ body size influences olfactory-driven response to potential host selection decisive volatiles, which can impact reproductive success and bark beetle population dynamics.