—Lancaster Farming, Saturday, April 10,1971
20
Rootworm
Populations of the northern
corn rootworm continued to in
crease rapidly throughout the
Commonwealth in 1970 and can
be considered pests of economic
importance in practically all of
the corn producing areas of
■Pennsylvania.
Growing corn in the same
Held for three or more consecu
tive years permits rootworm
populations to reach injurious
levels
The presence of the small,
pale green beetles on the silks
in August, and later along fence
rcws and fields where asters,
golden rod, and other flowers
are present, is usually j our
first indication of an infestation
in the area
The northern corn rootwoim
damages corn in two ways (1)
The small, pale green beetles
chew off the silks in late July
and August, and if they arrive
during the early stages of silk
ing, they can seriously interfere
with pollination
(2) The larvae feed on the
roots, weakening the root sys
tem. Growing plants are often
blown down by wind, and a
cmved stalk or -gooseneck” re
sults when the plant attempts
to right itself Mature plants
with damaged roots usually
lodge or fall to the giound, mak
ing harvest difficult and result
ing in considerable gram being
left in the field
The beetles deposit the major
ity of their eggs during Septem
ber and October in the soil
around the corn roots The eggs
remain dormant during winter
and spring
Then duung the latter half of
June they hatch, and the small,
slender, white larvae work their
way through the soil until they
find corn roots to feed upon
Most of the larvae will die if
corn is not planted m the field
where the eggs are laid.
The larvae mature in July
■and pupate in the soil The
beetles start emerging during
.the third week of July and reach
a peak by mid-August. They
usually congregate on corn silks,
feeding on the silks and pollen
The beetles are rather active
■and readily fly or tumble off the
plants when disturbed They
readily fly out of the fields to
other sources of pollen Few
beetles are noticed in the fields
after September 1.
Rotating corn for one yeai 01
more with any other ciop pro
vides a very effective method of
control
Control on Silks
Chemical control measures
against the adult beetles are
not suggested unless there is an
average of five or more beetles
Help Us
Serve You
If your organization didn’t
make our farm calendar this
week, it’s not because we
don’t like you or your or
ganization.
We may have missed it in
the rush Or maybe you foi
got to tell us.
Either way, we’d like to
extend our farm community
service to you.
To get on the Farm Calen
dar, remind us by calling
394-3047 or 626-2191 o. by
writing to Lancastei Fa’ru
ing, 22 E. Main St, LF'tz,
Pa. 17543. And help ir .i"c
you better.
Can Be a Serious Problem for Corn Producers
Editoi's Note The northern corn rootworm was re
ported by many corn producers and others kiwwledgeable
about corn as more of a problem locally in 1970 than th
blight
Since more and more Southeastern Pennsylvania crop
land is being turned to continuous corn, we can probably
expect the rootworm problem to continue or be worse in
1971 This is.true because the rootworm needs corn to sur
vive in significant numbers and it generally needs corn in
the same location for three years or more to become a real
ly serious pest
So, except for the few fields where chemical control
measures were taken last year to reduce the rootworm
populations or where corn is being planted in a field that
did not have corn last year, we can expect the rootworm
this year will be a more serious pest than last year.
- These and other facts about the rootworm are explain
ed in the accompanying bulletin by Penn State Extension
Service. Further details on control measures can be ob
tained from the local Extension office or from local faim
supply firms.
per ear and onlj if less than 50 reach damaging numbers
pei cent of the plants have silk
ed
Foitunately, most of the corn
in the Commonwealth is pol
linated by the time the beetles
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Once the ears are pollinated,
ro damage will result if the
silks are cut off
If necessary, beetles can be
killed with a spray of one
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pound actual per acre of either and lodging? Will this be the
malathion, diazmon, or car- thir for corn m
baiyl e
Control in the Soil
The actual damage to the
plant by the larval feeding on
the roots will vary considerably
with moisture, fertility, variety,
etc.
Therefore, the number of
rootworm larvae per plant
necessary to initiate control
measures is uncertain.
Some rootworm loss figures
indicate a population of four to
five corn rootworm larvae per
plant is the minimum number
necessary before it pays to
initiate conti ol measures.
At the present time, there is
no satisfactory way to predict a
population for a particular field
You will have to rely on the
history of the field and jour
own judgment
Ask these questions of your
self Did you see a great num
ber of beetles in the field last
August’ Was there root damage
as evidenced by goosenecking
A
WESTAUS
j me ctaiu \
SIIACC UMt
IKE STAItS
If the answer is yes to more
than one of these questions, you
should consider using control
measures for corn rootworms.
If crop rotation is not feasible
for your particular program, an
insecticide applied to, the soil
either at planting time or about
mid-June should be considered.
NEED EXTRA SEED
FOR EXTRA Aft
ACRES
?
For top producing corn,
sorghum, FD-100 alfalfa—Call:
Mervin W. Deiter
R. D. #3
Lititz, Pa. 17543
Phone 626-7515
II
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