ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

WOOD BORERS
Mitchell and Martin (In Press) suggest that prescribed burning to reduce fuel
loads of residues serves two functions: 1) it not only consumes the residues, but
also 2) attracts wood borers to the larger partially burned or unburned logs.
Borers will initiate decomposition by loosening the bark, creating holes in the wood
and introducing wood-destroying fungi. Evans (1 971 ) suggests that the role of
Melano hila wood borers should be considered in any prescribed burn program, not
h e
of their usefulness in residue deterioration but also because of their
contribution to fire-induced increases in species diversity. Dahl (1971) found no
relation between the mortality of Monochamus wood borers and the height of lodgepole
pine slash above the ground in prescribed fires of low and moderate intensity,
a1 though at the ground level Monochamus mortality was increased.
OTHER INSECT SPECIES
Several species of weevils, some cone and seed insects and some other insect
species that spend a portion of their 1 ife cycle in the forest floor, are also
involved in the interactions of residue and fire management.
Earlier 1 mentioned that the killing of pine seedlings by two weevils, the
pales weevil and pitcheating weevil, is influenced by the time of year during which
timber is harvested. Fox and Hill (1975) studied the effects of prescribed burning
in standing and cutover areas on the behavior of these two weevil species and found
that: 1) the pales weevil showed a positive preference for cutover areas, but
residues and debris burned after logging were a deterrent for this species; and
2) both burned and cutover areas were attractive to the pitcheating weevil. These
differences in the relative attractiveness of burned and unburned areas can influence
the management of pine forest land, especially when prescribed fire is used in
preparing the site (Fox and Hill 1973).
Prescribed fire can aggravate damage to conifer seedlings by another species of
weevil. In British Columbia, the weevil, Steremnius carinatus Boh. recently began
burning of surface residue,
causing significant damage to seed1 ings. m e d
". . .often necessary to reduce brush competition for seedl ings, destroys the natural
vegetation and materials the weevils normally eat, and focuses the attention of the
weevils on newly plwtted seed1 ings" (Condrashoff 1969). "In some plantations,
weevils have killed Qr damaged over 40 percent of Douglas-fir seedlings planted on
recently logged and burned sites along the west coast of Vancouver Island (LeJeune
1962).
Logging and residue removal has been sh~wn to kill sugar pine cone beetles,
Con0 hthorus lambertianae Hopkins. In the laboratory, Bedard (1966), found high
+tes in these beetles exposed to temperatures greater thqn 47" C, indicating
that e
high tem eratures from direct sunlight could have the same effect.
Bedard (1966) noted hat when logging operations open up the tree canopy, and when
the residues have been removed, ideal conditions of radiation are establ ished far
high temperature mortality of this beetle. In seed production areas in the Lake
States, burning is reported to be effective in controlling the red pine cone beetle
(Miller 1978).