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What to look for
Research indicates the potential for insect problems in conservation tillage systems is
about the same as any other system.
Pests found to have a greater potential to cause damage in conservation tillage systems
are black cutworms, slugs, stalk borers, and wireworms.
Cutworm moths lay their eggs in the crop residues. Slugs (which are mollusks, not insects)
survive and develop under residue-covered soils, which are usually cooler and wetter. Stalk
borer and wireworm increases are usually related to certain types of weeds or cover crops.
Most of these pests are almost always found in corn production but seldom
exceed economic thresholds for soybeans. Bean leaf beetles, grasshoppers, seedcom
maggots, and occassionally white grubs are most likely to require treatment in soybeans.
Biotech example:
Bt corn carries a gene which offers protection against European Corn
Borer. The gene was isolated from a bacterium (known as Bacillus thuringiensis or Bt-
a natural insecticide). A biotech method allows the gene to be placed into the corn
which is then bred to create a special hybrid. The gene allows the new line of corn plants to
produce a protein that protects the plants from certain insects.
A balance?
Despite greater potential for certain insect pest problems, conservation tillage seems
to have avoided the worst of the potential offenders. One reason may be its ability to
attract beneficial insects.
In general, reducing the disturbance of residue in the top few inches of soil favors
the survival and development of ants, ground beetles, rove beetles, and spiders
which often feed on insects.
Weed pressures and cover crops play a role in this balance. Weeds can attract
black cutworms, billbugs, hop vine borers, and stalk borers. Corn planted into cover
crops or pastures may experience greater problems with armyworms, webworms,
white grubs, and wireworms. An early kill of weeds or cover crops may help the
seedbed avoid some of these insect problems.
At the same time, slight increases in weed presence, at least during portions of
the season, can attract parasitic wasps that feed on the nectar or pollen from flowering
weeds and also serve as a worthy predator for insects.
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Management considerations
Whether pests have a significant impact on a crop production system depends on
several factors including weather, planting dates, tillage system, and crop rotation, so
timely field scouting and accurate field record keeping are essential in identifying
the correct pest management decisions.
Combining the strategies for IPM (page 15) with
an understanding of changes in insect populations will help to manage insects successfully.
Table 9 (next page) lists expected population
changes for some of the most commonly found pests in conservation tillage systems.
Self-contained "boxes" of insecticide can now be mounted on planter units for precision
application and safe handling.
Bioengineered crops
Bioengineered crops offer another line of defense against potentially damaging
pests. For example, Bt corn has genetic resistance to the European corn borer (see
sidebar). As part of an IPM strategy, use of these types of crops should be balanced
with other successful techniques.
Additional tips
Combine IPM strategies with the following tips to ensure insect pests pose no more
threat for conservation tillage than systems that plow under the crop residue:
 Understand the relationship
between crop rotation and
insect biology.
Properly select and place soil
insecticides.
Use insecticide seed treatment
when recommended.
Control weeds effectively
Understand and accurately
identify insects, both
beneficial and harmful.
Understand current economic
thresholds and treatment
guidelines.
Make timely insecticide
applications when necessary
Ensure labor is available for
field scouting.
Use insect- and herbicide-
resistant crops in rotation with
other pest management
strategies.
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