Spatial distribution and mapping of Curculio elephas Gyllenhal in holm oak (Quercus ilex L.)

Abstract

The weevil, Curculio elephas is one of the most important carpophagous pest of holm oaks and chestnut trees in Spain. The present paper performed during a four year period in an economically exploited holm oak forest area in Southern Spain, investigated the chestnut weevil spatial distribution using both classic methods (infestation indices, dispersion indices, fitting to statistical distributions) and by elaborating larval density maps. Our main findings were: 1) a very high incidence of C. elephas was detected on the holm oaks of the experimental plot, with 32-57.4 % of the acorns infested by the weevil; 2) dispersion indices, statistical distributions and larval density maps confirmed that C. elephas had an aggregated distribution and the spatio-temporal stability of its population over long term periods; 3) a direct relation was detected between the weevil infestation and larval density indices and the medium size of the acorns. These results indicate that the annual spatial ditribution of C. elephas was heterogeneous and that it was possibly related, among other factors, to the distribution of holm-oak with acorns inside the forest and to their quality and degree of ripeness.