Geostatistical analysis of gypsy moth outbreaks in Sardinian oak forestsusing a geographical information system

Abstract: Populations of the gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae) inSardinia were studied with a geostatistical model. A geographical information system wascreated by joining the gypsy moth egg mass counts recorded at 282 permanent monitoring sitesfrom 1980 to 2004 and the climatic, vegetational, geomorphological and pedological features ofthe sites. The frequency of gypsy moth outbreaks during the study years was affected by thepredominant host tree, slope, elevation and temperature of the monitoring sites, while nocorrelation was found between the outbreak frequency and exposure, rainfall and soil type.Spatial distribution of the gypsy moth was analyzed with geostatistical methods. Cokriging withoutbreak frequency as a covariate was found to be the most suitable technique to estimate thegypsy moth egg mass abundance, showing a spatial correlation within a range of 18.5-53km.Distribution maps of the gypsy moth in Sardinia were created to show the outbreak foci and thespread of gypsy moth infestations in each monitoring area. Our findings provide a technical toolto predict gypsy moth distribution and define the treatment areas, thus helping to develop rationalgypsy moth management programs.