AUTOMATED DETECTION OF PINE PLANTATION PRONE TO WOOD WASP INFECTION IN CENTRAL CHILE

摘要

There are more than 40 different species of wasps that belong to the Siricidae family (known as Horntail or wood wasp). But only Sirex Noctilio is able to affect healthy trees seriously. Principally it affects pine plantations (Pinus Radiata, Pinus Sylvestris, Pinus Nigra and Pinus Pinaster). A mortality rate of 80% is possible for affected trees within such plantations. Since 2001 it has also be detected in Chile, where it was found first in the Valparaiso, Los Lagos and Araucania regions. In 2009, Sirex Noctilio was detected in the Biobio region, one of the most important regions for the national wood production, based on Pinus Radiata. For this study, that aims to provide information about pine plantations prone to Sirex Noctilio infection, two multispectral ASTER images of an affected area in the Biobio region are used in order to compare the evolution of the plague during summer 2010/2011. For both images, the Normalized Difference Vegetation Index (NDVI) is calculated in order to detect healthy and stressed vegetation. A comparison of the NDVI for both images shows, that photosynthetic activity has decreased within the study area and that this not only occurred in the affected plantations, but also in others which in 2010 have been reported intact. In particular, plantations stressed by Sirex Noctilio show a NDVI decrease of about 20%. NDVI for former healthy plantations has almost reached similar values as for infected ones in 2010, so they are vulnerable to a Sirex Noctilio infection in the near future.