ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

The large aerial spray programs against the eastern spruce budworm haye been
justified, in part, by the claim that not to take some kind of direct action would
be to risk the development of thousands of acres of dead spruce-fir forests that
when blown down could create a tangle, piled like criss-crossed matchsticks, that
would not only create a tremendous fire hazard but also would make fire-fighting
nearly impossible (Maine Forestry Dept. 1973). It has been said that "while such
destruction has occurred historically and nature would in time heal the wounds, the
risk in the present context of millions of Americans with all their needs and desires
is quite unacceptable" (Maine Forestry Dept. 1973).
Most of us are aware of the controversy generated by using DDT against the
Douglas-fir tussock moth in Oregon early in the 1970's. Not so we1 1 known are
claims that the residues created by that insect predisposed defoliated stands to
wildfire. Heavily-damaged stands were reported to be especial ly susceptible to
wildfire (USDA, FS 1975a), and increased fire risk and fire protection costs were
listed among the several disadvantages to not using direct control with DDT or other
chemicals (Ellefson 1974). In addition to 852 million board feet of merchantable
timber killed by the Douglas-fir tussock moth (with a loss value of $28.1 million),
an additional $30.8 mill ion in losses occurred In the form of damage to immature
trees, reduced growth, increased reforestation expense, and increased fire protection
costs (USDA, FS l975a). (.One might interpret these as economic losses only if they
actual ly reduced the a1 1 owabl e cut, ) Senator Robert Packwood (Oregon) was quoted as
saying, "had we used DDT last year, we would not have seen the awesome increase in
defoliation and environmental damage leading to increased fire damage in the affected
areas that we did" (Crisp 1974). And Oregon's State Forester, Ed Schroeder, estimated
that the "total economic impact on Oregon in terms of timber and growth lost, reha-
bilitation cost, increased fire protection cast, and diminished land value is $9.5
mil 1 ion. " He continued that "the esthetic and recreational appeal has been reduced,
because of these forest residues and Oregonians will face increased fire danger for
20 years" (Crisp 1974). Again, as with the mountain pine beetle, it remains to be
seen how serious the predisposition of Oregon forests to wildfires has been or will
be, as a result of the Douglas-fir tussock moth.
Other Insects
In his unpubl ished manuscript, Brunner (1 91 7) provides some interesting examples
of insects contributing to the predi sposi tion of trees to fire--1 ess dramatic perhaps
than the bark beet1 e and defol iator situations discussed above. He mentions several
species of insects that feed in the cambium at the base of trees killing the bark in
patches, In such cases, even light surface fires ignite and burn off the dead bark,
especially of the resinous conifers, leaving basal wounds, which are often mistaken
for fire wounds. He describes one situation where carpenter ants, Camponotus sp.,
often appropriate tunnels vacated by roundheaded wood borers, Pachyta sp., and " . . .
so honeycomb the bark with their mines as to provide a draft through it for a fire
which, on this account, is able to scorch the cambium underneath, even on trees with
very thick bark."