Of Drought and a Beetle
Frank Shortt
Infestation of Bark Beetle
Two thirds of all trees affected by the little bark beetle in Eldorado County have been on
government land. How can such a small beetle instigate so much devastation?
Drought not only causes our water table to shrink, but affects so many other areas of our
lives. Wild animals are decimated, the fish population has to seek other water sources
for reproduction runs, humans must ration drinking water, and our pine forests suffer
greatly because trees become more vulnerable to infestations of insects, namely the bark
beetle.
When pine trees lack water they become weak, thus inviting the bark beetle to live off
them. There have been well over half a million trees decimated in Eldorado County
alone due to the four year drought and the attack of the bark beetle. Governor Brown
declared a state of emergency in all the affected counties in 2015. This report covers only
Eldorado County.
Bark beetles reproduce in the inner bark (living and dead phloem and cambium
tissues)of trees. Many species, such as the mountain pine beetle (Dendroctonus
ponderosae) attack and kill live trees. Most, however, live in dead, weakened, or dying
hosts. Pine bark beetles (Ips sp. and Dendroctonus sp.) feed primarily on the inner bark
(phloem tissue). This has the same effect as girdling (peeling off the bark) of the tree.
Damage caused by their feeding acts as an internal tourniquet cutting off the flow of
nutrients from the leaves to the other parts of the tree. As the damage progresses, sugars
and other complex compounds cannot be translocated downward from the leaves to
non-photosynthetic areas of the tree. The beetle can also introduce a blue stain fungus
which grows into the wood (xylem). This fungus prevents water from being transported
upward to the leaves. Both of these factors contribute to the decline and death of
colonized trees. It is amazing how much destruction has taken place in the affected areas
in such a short time.
The question has arisen among residents of outlying areas of Eldorado County as to why
some properties suffered greatly while some properties were unaffected. Some oldtimers have contributed the saving of trees on some properties to two factors: 1. There
must have been underground springs on some properties, and 2. Properties that were
occupied had septic systems that allowed leeching of water to surrounding trees thus
giving them enough moisture to remain healthy. Both these theories are conjectural, but
as good an explanation as any provided by officials of the County.
Tree Service owners are so overloaded that they often do not have time for individual
property owner’s requests. Huge log loading machines can be seen in all forest
neighborhoods lifting tree debris and even large logs into chipping machines ridding the
forests of affected and downed trees. Logging trucks can be seen on a regular basis
traveling to and fro from sawmills to Eldorado forests. There should be no shortage of
pine lumber for many years to come. Miraculously, the cedar and redwood populations
have been spared this devastation. Stumps and large brush piles are all that remain of
some pine forests. Mother Nature has ways of thinning out the trees and underbrush
even if the U.S. Forest Service does not seem to have funds for this much needed service
in our over populated forests. Some residents who have properties adjacent to National
Forests say “sensible logging could be allowed to render this overdue benefit to our
forest lands.”
Many prayers have been uttered that we do not have a similar drought such as has been
experienced in the last four or five years. Drought not only affects Pine trees but also all
other flora and fauna in any given area.