Spread of Western Corn Rootworm Variant
The western corn rootworm is the biggest insect concern in
corn for the 2007 planting season. The variant western corn rootworm is not controlled by crop rotation because the eggs were
laid in a soybean field that is going to be planted to corn the next
year. The variant eggs will then hatch and feed on the first year
corn roots.
 In 1986, the western corn rootworm larvae appeared in first
year cornfields in Ford County, Illinois. By 1996, this variant continued to spread into east central Illinois and northwest Indiana.
The colored map demonstrates the movement of the western
corn rootworm variant by year. The variant continues to move
north and west in Illinois. The counties in purple are new additions to the spread of the problem. The counties in gray need to
be scouted for the problem during the 2007 growing season.
The scouting method for the western corn rootworm is a good
idea for scouting in 2007 for the 2008 corn crop, but what if a
producer doesn’t know his pest levels for the 2007 corn crop? If
a producer is on the edge of the variant area or in the scouting
area, he can setup check strips in his fields. A producer can
choose to use a granular soil insecticide, High rate Poncho, or
YieldGard Rootworm protected hybrid across the entire field and
leave a strip through the field without insecticide control. The
producer could also choose not to use insecticide control on the
entire field, except for a check strip in the field that is a granular
soil insecticide, High rate Poncho, or a YieldGard Rootworm protected hybrid.
The western corn rootworm continues to adapt to control
methods. Crop rotation is no longer an effective method of control in portions of Illinois, Indiana, and Michigan. In Nebraska,
starting in the 1960’s, the western corn rootworm beetles were
sprayed before egg laying in continuous cornfields to prevent
larvae feeding on the roots of the next season’s corn crop. By the
mid 1990’s the western corn rootworm beetle were found to be
resistant to Penncap-M and Sevin
insecticide in Nebraska and the
control option was no longer
effective. This insect continues to
change. There is a growing need
to be concerned about insect
resistance. Remember to follow
all insect resistant management guidelines with YieldGard
Rootworm protected hybrids.
YieldGard Rootworm protection is the most effective tool
available for use against this
pest. If these IRM guidelines
are not followed, it could be
another date of new resistance
in the insect history book.
Sutter, G.R. 1999. Western Corn Rootworm. Handbook of corn
insects. Entomological Society of America, Lanham, MD. |
