Identification of the specific volatile organic compounds emitted by Anoplophora glabripennis (Moschulsky)
by Ramona Irina Gloria Fanny Makarow
Date of Examination:2020-02-04
Date of issue:2020-04-21
Advisor:Prof. Dr. Niko Balkenhol
Referee:Prof. Dr. Niko Balkenhol
Referee:Prof. Dr. Peter-Michael Kaul
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Abstract
English
The globalisation and the increasing international trade have raised the number and risk of introduction of foreign species and invasive pests for years. Although native species have adapted to the native habitat over many years and generations, invasive intruders often possess characteristics that are superior to native species. Thus, and because of a lack of natural enemies, they bear the potential of decimation or complete displacement of the native species; furthermore, the introduction of pathogens or nematodes as a vector possesses a high damage potential. The available measures of the local plant protection services to combat invasive species are confined. They are limited to the felling of infested trees or plants and regular controls within the infested area. A spread of single infestations can thereby be prevented, but undetected infestations can unimpededly spread, which points out the main challenge: the detection of the species. This concerns the infestation in open land as well as the single animal on its path of introduction. Concerning the development of new adequate detection systems for invasive species, there is only little research activity going on. For other fields like detection of explosives or narcotics, the research activities date back for more than one decade and consequently there are detection systems available, which are, for example, used for explosive detection in airports. The detection principle bases on the chemistry of these substances. When adapting the development steps for a detector of invasive species, the first step (i) is the investigation of the chemical substances emitted by the species of interest. Beyond that, for living organisms it is relevant to investigate (ii) if their chemical signature is specific and if a distinction to native organisms is possible. This dissertation focusses in these two major issues on the example of Anoplophora glabripennis (Moschulsky) (Asian longhorned beetle, ALB). In part I the chemical substances emitted by Anoplophora glabripennis in different development stages (imago, larva, oviposition) were investigated. The focus of the investigation was on the volatile organic compounds (VOCs), which are available in the gas phase for a detector. They were analysed qualitatively by thermal desorption coupled with gas chromatography and a mass selective detector. Altogether 229 substances were identified: 34 from larvae, 19 from imagines and 176 from ovipositions. Ovipositions of two generations were analysed, both over an 8-week period with focus on ageing and repeatability. (+)-α-Longipinene occurred in 100 %, (+)-cyclosativene and α-cubebene in 99 % of all oviposition measurements. The monoterpene ocimene occurred from ovipositions in a later development stage. 2,4-Dimethyl-1-heptene and (+)-cyclosativene were detectable in all three ALB sample types. With the objective of distinction to native insect species, in part II some native insect species were analysed, which often lead to mistaken identification of species by visual determination. Overlap between ALB and native insect species were identified for Saperda carcharias Pupa and Cossus cossus larva for 2,4-dimethyl-1-heptene. No overlap for sesquiterpenes were identified. Beside native insect species, in part II other VOC sources that determine the chemical background of ALB’s habitat were investigated: healthy, not infested host trees in open land and stressed trees, whereas the stress originates from mechanical damage and poor water and light supply. The infestation of a tree also leads to stress as there is a damage in the tree’s internal channels of supply with the consequence of a lack of supply. Generally, stress leads to a change in the VOC pattern of trees. To ensure that the VOCs determined from ALB infested trees originate from the ALB infestation and not from general stress, the mechanically stressed trees were also analysed. Altogether 169 substances were identified. 11 substances occur from ALB infested or mechanically damaged trees, but not from healthy trees. (+)-Cyclosativene, (+)-α-longipinene, copaene and caryophyllene are detectable only from ALB-infested Acer not from mechanically damaged or healthy Acer; however, these substances are also emitted by healthy Salix and thus bear the potential of mistaken identification. 2,4-Dimethyl-1-heptene is among all tree samples exclusively present in the ambience of ALB-infested trees. It is rarely detectable from native insect species’ samples. As a result, the expansion of the ALB VOC pattern to (+)-cyclosativene, (+)-α-longipinene, copaene and 2,4-diemthyl-2-heptene and the monoterpene 3-carene and ocimene can be interpreted as an ALB-specific VOC pattern. In order to verify this pattern, in part III some experiments were carried out with sniffer dogs. At present sniffer dogs are the only available detectors for ALB. They are commonly conditioned with biologic ALB samples and trained to indicate ALB-infested material. On the basis of this assumption differently setted experiments were carried out with a synthetic ALB mixture consisting of standards of the substances (+)-cyclosativene, (+)-α-longipinene, caryophyllene and ocimene. The use of copaene was not possible, because standards for these sesquiterpenes were not available at all. The mixture was applied on a developed scent carrier. In different experiments different sniffer dog teams confirm the recognition of the ALB-mixture as ALB-characteristic. In summary, the method of extracting specific VOC patterns could be a promising strategy to prevent an aggravation of the invasive species’ problem. With the method more invasive pests like Agrilus planipennis or the genus Monochamus, the vector of the nematode Bursaphelenchus xylophilus can be analysed and their specific VOC pattern added to ALB pattern. For invasive pests of the same species as ALB e.g. Anoplophora chinensis, it is likely that the VOC emission is similar with identical specific VOCs. The extraction of specific VOCs from further invasive pests combined with the VOC pattern of Anoplophora would cover relevant and threatening pests from this decay in Europe and Northern America. The development, approval and implementation of suitable detectors for import controls would be the next step to contribute to the protection of Europe’s biodiversity and forest habitats on the basis of these results.
Keywords: Anoplophora glabripennis, volatile organic compounds, TD-GC/MS