LARVAL DEVELOPMENT VARIATION AND ADULT EMERGENCE IN THE CHESTNUT WEEVIL CURCULIO-ELEPHAS GYLLENHAL (COL, CURCULIONIDAE)

The chestnut weevil Curculio elephas is an important pest of the Europ ean chestnut Castanea sativa. Our results show that, in the Rhone regi on, most larvae leave chestnuts from October to early December and imm ediately burrow into the soil where they overwinter. On average, 95% o f larvae leave the fruit after the chestnut has fallen. Adult emergenc e occurs the following summer-fall, from mid-August to early October. Weevils burrowing in November (cohort 2) usually emerge later than tho se burrowing in October (cohort 1). Whatever the cohort, some larvae e xtend diapause over several winters but frequency of prolonged diapaus e is greater in cohort 2. Because of great emergence variability and p rolonged larval diapause, efficient chemical controls may be costly an d damaging to the environment. Conversely, collecting chestnuts under trees combined with biological control with pathogenic fungi may drast ically decrease the population density of this pest without ecological damage.