The Ottawa free trader. [volume] (Ottawa, Ill.) 1843-1916, 1883-02-10
The COrn-RoOt Worm.

Prof 5. A. FORBES, State ehtomologIs, OF
Illinois, sends Us the following description
and life history Of the cOrn-root worm,
Di0brotjca loagic0rajs Say, which has in
jsome cases reduced yields OF cornfeius IL
that State from IS to IS per cent, but the
damage Is rarely over ) to 20 per cent:
The corn.root worm, in the form in
which it affects the roots OF corn, is slen-
der white grub, not thicker than PIN,
from one-fonrth to three Fights Of an inch
10 length, with a small brown head, and
six very short legs. 1t commences its at
tack in May or June, usually at some dis
lance from the stalk, toward which it eats
It's way 6e meath the epidermis, killing the
root as fast as it proceeds. Late IN July or
early in August it transforms in the
ground near the base of the hill, changing
into white pupa, about fifteen hundret1s
of an inch long and two.thlrds that width,
looking somewhat like an adult beetle, but
with the wings and wing covers rudimen-
tary, and with the legs closely drawn up
against the body. A few days later 1t
emerges as perfect insect, about one,fifth
OF an inch in length, varying in color from
pale greenish brown to bright grass-green
and usually without spots or markings of
any kind. The beetle climbs up the stalk,
living on fallen pollen and upon the silk
at the tip of the ear until the latter dies,
when a few Of the beetles creep down be-
tween the husks, and iced upon the corn
ITSELF while others resort for food to the
pollen of such weeds in the field as are at
that time in blossom. In September and
nNtN bnr h.n u 4
upon or about the roots of the corn, aud
most Of the beetles soon after disappear
from the field They may ordinarily be
found upon tho lateblooming plants, feed.
ing as usual upon the pollen of the flowers
and also to some extent upon moulds and
other tungi, and upon decaying vegetation.
There can be no further doubt that the in.
sect is single. brooded, that 1t by bernates in
the egg as a rule. AMI that this does not
hatch until after the ground has been
p.oTed and planted to corn IN the spring,
probably in May and June
Although the adult beetles, when MI
merOus, do some harm by ealing the silk
before the kernels are fertilized by the pol.
len, anu also destroy occasionally a few
kernels IN the tip Of the ear, yet the prInci
pal injury is done by the larva in its attack
upon the roots. Although the roots pene.
trated by the lafva die and decay. thrifty
corn will throw Out new ones to replace
those lost The hold Of the stalk upon the
ground is often 80 weakened that slight
wind Is sufficient to PROSTATE the corn.
Under these circumstances 1t will often
throw out new roots from the joints above
the ground, thus rallying to certain ex.
tent against serious injury Az The resnlts
of numerous observations, 1t is seen that
little or no mischief Is done eIcep, In fields
that have been in corn during the year or
two preceding, and frequent change of
crops is therefore complete preventive
Beyond this, the life history of the insect
gives US little hope of fighting it effectual-
~ except at too great expense, as the eggs
and worms are scattered and hidden IN the
ground, and the perfect beetle Is widely
dispersed throughout the field"