Effect of weather on ips typographies (coleoptera curculionidae) phenology, voltinism, and associated spruce mortality in the southeastern alps

Abstract

Summer drought associated with high temperatures recorded in the last few years has given rise to outbreaks of bark beetles developing in weakened host trees. The aim of this study was to investigate the possible weather effect on the biology of and damage caused by Ips typographis L. in the southeastern Alps. The study was carried out recording temperature (1962-2007), precipitation (1922-2007), and the damage caused by I typographus (1993-2007). In addition, data from pheromone-baited traps (1996-2005) provided information on the main periods of flight activity of I. typographic From 1922 to 2007, precipitation during March-July has decreased ∼200 mm (-22%), whereas since 1962-2007, mean temperatures during March-July increased ∼2°C (+13%). Damage caused by I. typographic was inversely correlated with March-July precipitation from the previous year but not correlated with temperature. Increases in spring temperature did not affect the development timing of the first generation, but only changed its onset. Earlier swarming of both overwintering beetles and first-generation offspring (∼20 d sooner over 10 yr), and the early start of the second generation permitted more complete development of the second brood. Voltinism in this species is discussed in relation to thermal and photoperiodic thresholds, indicating that the occurrence of a third generation is limited by the summer photoperiod rather than by temperature. In conclusion, results suggest that spring drought increases damage caused by I. typographic in the following year, whereas warmer spring affects insect phenology. © 2009 Entomological Society of America.