Bionomics of the four‐eyed spruce bark beetle, Polygraphus rufipennis (Kirby) (Col., Scolytidae) in Newfoundland II. Host colonization sequence

Abstract

Abstract: The four‐eyed spruce bark beetle, P. rufipennis, is a phloeophagous bark beetle restricted to Abietineae hosts in northern and mountainous area of North America. Projected wood shortages in Newfoundland have focused attention on the bark beetle and its role in contributing to black spruce mortality. Our findings disclosed that colonization on felled and standing trees by P. rufipennis followed the typical host selection sequence of scolytids, notably, emergence, dispersal, selection and establishment. All brood stages except eggs overwintered in black spruce, however, the majority of overwintering stadia consisted of larvae and callow adults. Adult mortality was significant during winter, especially in standing severed and felled trees. In Newfoundland, P. rufipennis had 1 generation and produced a spring and summer brood. Four weeks after establishing a first brood, parent adults re‐emerged to establish a second brood. Development from egg to adult took ≅2 months. P. rufipennis of either sex initiated attack at mean densities per 100 cm2 of 8.1 and 9.3 on felled and standing‐severed trees, respectively. Densities were significantly lower at 4.7 per 100 cm2 on standing unsevered trees. Following copulation, males stayed with the females and exhibit guarding behaviour by occupying the entrance hole. Significantly higher numbers of galleries were established on trees felled in shade than in full sunlight. Black spruce attacked by P. ruipennis were often secondarily attacked by Dryocoetes affaber and Crypturgus borealis. Other associates included Medetera sp. and the cylindrical bark beetle, L. intricatus.