Blue Sap?

RandyFulle randyfulle at
Thu Jan 29 23:01:06 EST 1998

Good Evening Larry,

A quick response for you.

>I know little boring beetles leave blue trails because of a fungus they
>carry around on their feet.
Most, but certainly not all, bark and wood inhabiting beetles are capable of
carrying fungi on the outer surfaces of their bodies. The classical senario (if
there is such a thing :)) for the 'true' blue stain (as seen in end cuts of
pines) is the fungi is carried into the tree by the beetle in a special
declavity in the underbody called the mycangia. This pouch contains many fungi
species, but a special relationship exists between many beetles and their
mycangial fungi. Such a special relationship exisits between the ambrosia
beetles and the blue stain fungus Ceratocystis minor. The fungus is actually
necessary for this beetle to colonize a host tree. The fungus blocks off water
transport routes, thus drying out the tree for sucessful colonization. The
young pupae of the beetle also feed on the fruinting bodies of the fungus and
when they emerge to fly off they carry the spores of this fungus with them in
their mycangia (sounds like a vicious cycle doesn't it).
Blue stain fungi are associated with many, many beetles. Especially those in
the bark beetle genera. Some need the fungus for sucessful attack and some are
inhibited by the mycangial fungi (i.e., Southern Pine Beetle).

A very interesting symbiosis to study.

Randy Fuller
Forest Pathologist/Entomologist

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