The table below describes symptoms associated with various stages of SPB attack. Development of all stages continues throughout the year, slowing considerably in the winter and accelerating in the spring and summer. One life cycle or generation from egg to adult may take from 26 to 54 days depending on the season. Over a temperature range of approximately 60 to 85 degrees F, the length of time for each stage varies as indicated below . After the pioneer beetles successfully colonize a susceptible host tree, the beetles and the host tree produce chemicals that attract additional flying adult beetles.
Attacks spread up and down the trunk over the course of three to five days.
Small, light yellow to white pitch tubes usually form where the beetles enter the tree along the entire trunk length. These masses of pitch are about the shape and color of popcorn, and can be the same size or slightly smaller. Especially weak trees may not produce pitch tubes, but reddish boring dust in bark crevices or cobwebs at the base of the tree is evidence of infestation. During gallery construction, the adult beetles introduce a blue-stain fungus. Along with the girdling effect of gallery excavation, the fungus contributes to the death of the tree by eventually plugging the tree's water-conducting tissue.