ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

Bark and engraver beetles infesting thinning and logging residue are only a few
of a series of insect species that successively inhabit and feed on slash and other
forest residue until the wood has disintegrated completely (Adams 1915; Savely
1939). Thomas (1955) lists a series of four groups of arthropods that successively
infest red and white pine logging slash: 1) bark beetles, 2) borers and weevils of
the fami 1 ies Cerambycidae, Buprestidae, Pythidae, and Curcul ionidae, 3) parasites ,
4) predators entirely dependent for food on the presence of insects in the first two
groups,
In addition to bark and engraver beetles, thinning and logging slash predisposes
forests to other types of forest insects (fig. 10). In Montana, Fell in and Schmidt
(1 966) observed a very close re1 ationship between residues created by thinning young
lodgepole pine stands and infestations of a needl e-eating weevil, Magdal is gentil is
Leconte. Although they were apparently neither feeding on or breeding in the residue,
weevils were attracted to the thinned stands and fed on current year needles of crop
trees, often resulting in a loss of 75 to 100 percent of the foliage.
Fel lin (1973)
found that time of thinning was significant in determining whether these crop trees
would be infested; when residues were not created before late July to mid-August,
Magdal i s infestations did not develop. In 1974, Magdal i s populations were attracted
to lodgepole pine thinning slash throughout 700 acres ln the Moose Creek drainage of
the Lewis and Clark National Forest in west-central Montana. There was heavy defolia-
tion of the 1974 growth in most areas; in some stands 100 percent of the new growth
was destroyed (Hamel and McGregor 1974).
Figure 10. --AZthough fire, wCndthrow, and other natumZ factors create
substantiaZ amounts of residue, predisposfng forests to insects,
man--through his own management actions--atso creates vast amounts
of forest residue though 2ogg-i-ng dash, precommciat thinnings,
etc., predieposing forests to a wide vadety of insect species.
-f-
In red pine stands in Ontario, Ma dalis perforatus causes damage to young trees
as a result of adult feeding, but popu ation increases are usually related to pruning
operations or mortality in young stands and not to thinning in older stands (Martin
1965).
In the Southeast, other species of weevils are influenced by forest residues,
including stumps, also depending on when timber is harvested. In east Texas, Thatcher
(1960) determined a relationship between the season in which pines were cut and
emergence of the pi tch-eating weevil , Pachyl obius picivorus (~ermar) . Later, Speers