Evolution of the spatio-temporal distribution of Xylotrechus arvicola (Olivier) (Coleoptera, Cerambycidae) in La Rioja vineyard (Spain)

Xylotrechus arvicola (Olivier) (Coleoptera, Cerambycidae) is a polyphagous species. Its larvae can be found feeding on different wooden cultivars and wild trees. Since 1990, this pest has become an important sanitary problem affecting vineyards in northern and central Spain (2000-2008). A study based on the distribution of the number of exit holes perforated by adults in the vinestocks was carried out for 9 years in a plot located in La Rioja wine producing region (Spain). The percentage of affected plants grew each year, from 51 % in 2004 to a level of 96 % in 2008. In 2005, dead vines began to appear with damage caused by the insect. In 2008 it increased to 17 % of the vines. This data indicated a very heavy attack of the insect which is becoming a very serious pest. The number of exit holes is directly related to the number of affected vinestocks and also dead plants. The spatial distribution of the holes of X. arvicola was studied using Taylor's Potential Law and Iwao's regression, as well as elaborating maps of population density. Statistical techniques indicated a uniform distribution of the pest in the sampling plot. During the cited period, several aggregation centers could be observed with a long term spatio-temporal stability using the Cramer-Von Mises test.