Cross Section of Blue Stain Fungus Invading Tree Bole
This loblolly pine, Pinus taeda, was killed by southern pine
beetle. Or was it? Even though SPB received the blame for the death of
this tree, it alone is only partially responsible. An associate of the
SPB, Ophiostoma minus, a fungal microorganism better known as "blue
stain", occupies an important role in the life and death of bark beetles
and their hosts. During colonization, female beetles tunnel throughout
the phloem tissue of the tree where they lay their eggs. As carriers of
O. minus, the beetles induce thousands of low dosage fungal inoculations
over a large portion of the tree bole allowing the fungus to become well
established throughout the phloem before invading the sapwood (xylem).
Sapwood occlusion by O. minus contributes to the quick death of
SPB-attacked trees which is critical to SPB since the colonized sections
of the tree must die for the beetles to successfully reproduce.
