Trees, Fruits and Flowers of Minnesota, 1916: Embracing the Transactions of the Minnesota State Horticultural Society,Volume 44, from December 1, 1915, to December 1, 1916, Including the Twelve Numbers of "The Minnesota Horticulturist" for 1916
History
Trees, Fruits and Flowers of Minnesota, 1916: Embracing the Transactions of the Minnesota State Horticultural Society,Volume 44, from December 1, 1915, to December 1, 1916, Including the Twelve Numbers of "The Minnesota Horticulturist" for 1916
The curculio passes the winter in the adult stage under accumulations
of partly decayed leaves, among the closely-packed dried grass of
sod-covered orchards, and probably wherever suitable protection from the
winter may be found. Its depredations are usually worse near woods, so
it probably finds here very suitable places for wintering.
In the spring, when the fruit buds are unfolding, the beetles begin to
emerge from their winter quarters and feed to some extent on the
blossoms and tender leaves of the fruit trees. Mating soon begins, and
by the time the fruit is well set the beetles make this fruit the chief
object of their attention. The circular punctures in the skin are
feeding punctures, while the crescent-shaped ones are egg-laying
punctures. A single egg is deposited in a puncture, although several may
be placed in a single fruit. From one to eight eggs may be deposited
daily by an individual female, which may be continued for several
months. The great majority of the eggs, however, are deposited by the
end of eight weeks. These eggs hatch in from three to seven days, being
influenced greatly by the weather.
The egg hatches into a larva, or "worm," which bores into the fruit. It
becomes full-grown in from twelve to twenty days and bores out of the
fruit. It enters the soil, burrows to a depth of one-half to two inches,
and forms an earthern cell in which to pupate. In three or four weeks it
emerges as a full grown beetle and attacks the ungathered fruit and the
foliage. On the approach of cold weather the beetle seeks a protected
place in which to pass the winter.
The character of the injury is very nearly alike in all fruits. In the
plum the fruit often falls to the ground before mature. In seasons of
short crops very little fruit may remain to ripen. The punctures cause
the fruit to become mis-shaped and to exude masses of gum. The ripe
fruit becomes "wormy." The late varieties may be seriously injured by
the new generation of adults. In the apple the injury to the fruit is
about the same as in the plum, except that the infested fruit is not so
likely to fall to the ground and that the egg rarely hatches into the
grub there. The fruit becomes knotted and pitted. The late varieties may
also be injured by the new generation of adults. In the peach, cherry
and other stone fruits, the injury closely resembles that of the plum.
Although the plum curculio has some natural enemies that tend to reduce
its numbers somewhat, yet they are not important enough to be considered
as effective means of control. Some of these natural enemies are
parasites of various kinds, birds, chickens and the like.
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