Controlling Corn Pests 05/24 12:28
Now that the corn crop is planted, growers need to be diligent about
scouting for insect pests.
By Daniel Davidson
OMAHA (DTN) -- The 2007 corn crop is in the ground for the most part and now
farmers need to focus on their disease- and pest-management programs.
As far as pests go, farmers at this point in the season need to be on the
look out for grubs, maggots, wireworms and cutworms. These insects, which
attack and feed on germinating seeds and young seedlings, cause minor damage
before emergence that doesn't necessarily cut yield significantly. Control is
achieved through rotation (there's less damage planting corn after soybeans
than after another cereal crop like wheat or corn), soil insecticides or
seed-treatment insecticides. Much of the corn seed planted today comes treated
with either Cruiser or Poncho seed insecticides, and soon farmers will no
longer have the option to buy untreated seed.
Black cutworms, however, pose a much more serious threat, especially right
after emergence. Growers should scout fields for black cutworm at least once
per week for three to four weeks after the crop emerges. Black cutworms migrate
back to the Corn Belt each spring and lay eggs; the larvae then feed on emerged
Peter Hill, an agronomist with Mycogen Seeds, said the best places to look
for the pest include "where plants have not emerged, plants that have been
clipped off and are lying beside their stump or plants that have died within
the row. Sometimes they may have been clipped below the soil surface."
Soil- or seed-applied insecticides will help control infestations, Hill
said. But he adds that corn hybrids containing the Herculex I Bt trait are an
Corn rootworm larvae are another significant pest. Rootworm larvae feed on
roots and can cause significant yield loss, particularly in dry and windy
Hill recommends that growers be diligent in checking for root feeding and
identify common signs of corn rootworm, including brown scars on the root
surface, tunnels within the roots and root pruning. Soil insecticides and
hybrids with the rootworm Bt trait provide acceptable levels of control.
Growers need to remember that the Western corn rootworm beetle variant has
adapted to rotational practices by laying eggs in soybean fields instead of
only cornfields, Hill said. And the Northern corn rootworm beetle lays eggs in
cornfields, but those eggs can lie dormant in a field for two or more yields so
crop rotations are no longer effective control methods.
The European corn borer used to be the number one insect pest in corn.
Because the corn borer is a mobile insect, rotations with soybeans had no
effect on control. However the broad adoption of Bt corn has reduced the corn
borer population and damage levels to the extent that the pest no longer has
much economic consequence. Still, to be safe, many growers plant Bt corn with
corn borer protection as a risk management tool.
Daniel Davidson can be reached at firstname.lastname@example.org.
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