Attack strategy and development of Dendroctonus micans (Kug.) (Coleoptera: Curculionidae) on oriental spruce in Turkey

Abstract

Dendroctonus micans has been continuously colonizing the native oriental spruce forests after its discovery in 1966 in Turkey. Solitary females attack the trees and they usually do not kill its hosts. This study aims to contribute the understanding of this solitary attack strategy and development of D. micans on oriental spruce in Turkey. The pattern of tree infestation was analyzed from 2001 to 2004 and 2006 in 120 experimental plots. Field surveys were carried out in the north east of Turkey in Artvin, Giresun, and Maçka (Trabzon) from May to October of each year. A total 3010 trees were examined in plots. D. micans infestation up to 2 m of trees were examined and the successful and aborted attacks were recorded. Development stages and numbers of the beetles were recorded in the galleries. The sizes of the old brood chambers were measured in the abandoned and infested trees. The beetle was found in 95.8% of the plots, attacked 21.7% of the spruce trees, and was active in 11.1% of the attacked trees. The majority of the attacked trees had only one successful attack. 69.3% of the entry holes, were up to 1m, and 30.7% of them were between 1 and 2 m. The attack rate was limited in many trees but it was rather high (40 to 160 attacks on a tree) in certain trees. Females laid 51.4 eggs on average with maximum of 200. 3.7% larval and 4% young adult galleries were coalesced. 24.3% attempts of D. micans was aborted and 75.7% of them was successful. Numbers of wounded and unwounded infested trees indicated a significant statistical difference. D. micans attacked and established more often on wounded trees. 83% of the wounded trees, were attacked by D. micans.