|When new spots first become visible,
they may have only fight-green or yellow-crowned. trees (fig. 2) and not
display other stages of foliage fade. This is particularly true in late
spring and early summer. But by midsummer the typical expanding SPB spot
has dead or dying pines in various stages of discoloration (fig. 1). The
different foliage colors trace the beetle's spread through the forest. After
8-12 weeks, beetle-killed trees at the spot's origin drop their needles.
Next to these bare
|trees are red-crowned ones, most
of them no longer containing beetles. Then come yellow-crowned pines that
have been more recently killed. Newly attacked trees on the margin of the
spot will have green crowns, and from the air you will not be able to distinguish
these from unattacked trees.