Abstract
This study examined the biology of sugar maple borer (SMB), (Glycobius speciosus (Say)) (Coleoptera: Cerambycidae), a native woodborer that infests sugar maple (Acer saccharum Marsh.) and investigated determinants of host and stand susceptibility. Head capsule size was associated with gallery length to derive an estimate of five larvae instars. Thirty percent of larval mortality occurred during early larval stages, 27% during mid-larval stages, and 43% during late larval stages. Woodpecker predation was the only identifiable mortality factor. Beetles emerged between 316 accumulated DD (base 10oC) and 648 DD. Males emerged prior to, or simultaneously with females, and lived longer. Female fecundity was 41.3 ± 6 eggs which eclosed seven to 10 days after oviposition. Females possessing non-functional ovipositors represented a significant reproductive loss. Seventy-seven percent of infested trees had a single oviposition site. Seventy percent of oviposition sites, had only one or two larvae that successfully eclosed, penetrated the bark to the phloem-cambial interface, and began to feed. Beetles preferred southern and eastern aspects for oviposition which occurred preferentially lower on the bole. Lower oviposition sites offered some protection from woodpecker attacks for developing larvae. Differences in male and female morphology include longer and wider male antennae and male pronotal pits containing gland pores.
In a naturally infested stressed stand, beetles developed more quickly, i.e. gallery lengths were shorter, in more vigorous trees as represented by higher root starch content. SMB can complete development in healthy trees. Offspring of beetles forced to oviposit in vigorous trees in a healthy stand excavated shorter galleries and emerged from larger emergence holes. Maturation in a healthier host has the potential to shorten exposure to predation and to culminate in larger adults and potentially more fecund females.
Percent sugar maple basal area was the primary predictor of SMB presence in a stand, and as mean diameter of stands increased, the likelihood of presence decreased. SMB was more abundant in stands with a history of defoliation where soils provided poor growing conditions for sugar maple.