Villa G.1, Bonanomi L. 1, Guarino D. 1, Pozzi L. 1, Maspero M. 2
1 Demetra Società Cooperativa Sociale Onlus, Via Visconta 75, I 20842 Besana Brianza (MB), Italy
2 Fondazione Minoprio, Viale Raimondi 54, I 22070 Vertemate con Minoprio (CO), Italy
For some years on Italian territory has been detected the presence of two harmful species of insects of Asiatic origin: Anoplophora chinensis and Anoplophora glabripennis. Such cerambyicidae coleoptera represent a serious danger for our tree heritage because they attack dozens of tree species. The larvae of A.chinensis dig tunnels inside the base of the trunk and in the roots, while those of the congener glabripennis develop in the aerial part of the stem and branches. Their activity obviously involves a reduction of the stability of the tree leading to his death. The disease spreads quickly and the only way to contain it at the moment seems to be the removal of the affected plants. For this reason it is very important the monitoring and the early detection of the infestation. To this purpose has been initiated, with the support of Regione Lombardia, a three-year trial in order to evaluate the effectiveness of the diagnosis of the electronic nose in the identification of affected trees by A. chinensis in areal affected of Lombardia.
This preliminary stage of the research is planned to verify the possibility to employ the electronic Nose in the diagnosis of Anoplophora chinensis, on standing trees.
The sampling have been carried out with a pump that enables to collect the telluric air, sucked in correspondence of the selected subjects (fig.1), directly into containers suitable for the analysis. The instrumental analysis has been subsequently carried out in the laboratory within a time of maximum 12 hours from collection of the air. The sensorial analyzer
(Pen3 Airsense – PCA Technologies) consists of a sampling unity of the gas, a set of sensors and one computer for calculation and final assessments. The sensors are sensitive to a wide range of gas and the reaction mechanism is based on a exchange of oxygen between the volatile molecules and the metal films, which causes an exchange of resistance, recorded and related to the absorbed compounds. The recorded dates are finally processed by techniques of multivariate statistical analysis (analysis of the principal components and linear discriminating analysis).
The first preliminary test has been done by sampling the telluric air on 74 trees, all belonging to the genus Acer , of these, 62 were affected by A.chinensis. In detail, the survey has been carried out on live plants Fig. 1 The sampling have been carried out with a pump situated inside the green area of Boscoincittà (Milano) and on freshly cut stumps of affected Maple trees located on a felling site in Canegrate (Milano).
The subjects selected as affected showed irrefutable symptoms of the presence of A.chinensis. The healthy trees have been selected according to the indications of the constant land monitoring done by ERSAF in previous months. The affected trees have been subsequently removed, as a result of activities planned for the eradication and control of A.chinensis by ERSAF, and then it has been possible to verify the presence of the pathogen through the collection and counts of the larvae (Fig. 2)
The processing of the data recorded by the instrument has shown, for each session of the analysis, the discrimination between healthy subjects (grouped in a well defined cluster) and
affected ones; these last ones contrary to the healthy ones, show a high dispersion, that could also be determined to the high grade of infestation of the subject.
This step has enabled us to evaluate the use of the instrument for diagnostic purposes, it was found that there are a large number of sources of variability that require careful standardization of analysis and of sampling; there is also a strong local and temporal characterization. On the other hand the results show a clear and uniform mark of the healthy Maples and the instruments has correctly classify the suspect subject as healthy. The preliminary results obtained from these tests are very encouraging as the possible discrimination between healthy and affected trees would allow to use the instrument to diagnose the presence of Anoplophora. The research must continue in order to confirm and explore the potentiality of this technique in order to provide a valuable aid for the massal monitoring of trees in nursery and for the early eradication of possible outbreaks in new affected areas.
The use of the instrument would release the diagnosis by the subjectivity of the operator in detection of the visual symptoms, and would make it possible also on asymptomatic plants (it must be then established the edge of detection of the instrument, that means the capacity to detect the presence of A.chinensis from the very early stages of attack).