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Trenk, Fred B. (Fred Benjamin), 1900- / Forest planting handbook

Causes of failure in plantations,   pp. 14-16 PDF (814.7 KB)

Page 15

fifth year, the root system of most trees is sufficiently large to with-
stand some damage from grubs, without the tree dying.
  Rabbit injury, porcupine injury, and in some cases deer injury, oc-
cur in northern counties. During some winters, especially when snow-
fall is light, the losses are more noticeable.
White Pine Weevil
Pissodes strobi
  There are frequent outlireaks of the white pine weevil, one of the
worst insect enemies of white pine in Wisconsin.* While this insect
    A portion of a tip of a white pine with the exit holes of the white
  pine weevil. An adult weevil is on the twig.
does not usually kill the trees outright, by killing the terminal shoot
of the main stem, it causes the trees to grow badly forked and
crooked and may, under some conditions, render them valueless for
  The weevils are reddish-brown, snout beetles about a quarter of an
inch long with white markings on the wings. They pass the winter in
the litter beneath the trees. In the spring they emerge and gather
on the terminal shoots of the pine, generally on the trunk leader in
preference to those of the branches. Here, near the tip, they feed on
the bark and the female beetles soon cut tiny holes in it, placing their
eggs in these chambers hollowed out of the inner bark.- These eggs
hatch into larvae which bore downward through the leader and by
August have completed their feeding and are ready to pupate in these
tunnels. The adult weevils soon emerge and cut their way out of the
tunnels through the sides of the branches by making round holes
through the walls. Later they hibernate, there being only one genera-
tion each year.
  This insect can be prevented from doing serious injury under forest
conditions. Trees growing in a dense stand are less subject to weevil-
ing than those in open stands and also in dense stands the stimulation
of straight growth is so strong that practically all weevil injury is out-
grown. White pines growing under shade of hardwoods are not usu-
The author is indebted to E. 1 Chambers. State Entomologixt, for information
presented here on white Dine weevil and white pine blister rust.

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