Des Moines, Iowa
January 30, 2002
Entomologists across the Corn
Belt recorded a significant increase in European corn borer
(ECB) populations from 2000 to 2001, with second-generation
borers being especially numerous. What 2002 will bring is any
entomologist's guess, though history would indicate a year of
high ECB populations is on the horizon.
"European corn borer is a very unpredictable insect," says Kevin
Steffey, extension entomologist at the University of Illinois.
"In 2001, we saw a significant increase in second-generation ECB
throughout some areas of the state, particularly northern
Illinois. Apparently environmental factors such as the weather,
the relative lack of natural control measures and the quality of
the corn crop came together to enhance mating and egg laying."
In Minnesota, results of the annual Department of Agriculture
fall survey show a marked increase in the over-wintering number
of both biotypes of ECB common to the area - univoltine and
second-generation bivoltine. University of Minnesota
Entomologist Ken Ostlie reports that numbers appear to be
growing since the peak years of 1995 and 1996, and researchers
there are waiting to see if the high adoption rate of Bt corn
among the state's growers has any impact on the cyclical nature
of the insects. The state has seen an unprecedented number of
low-infestation years.
Typically, ECB populations fluctuate in a cycle that may range
from four to seven years. Populations peak and subsequently take
a significant drop. This cyclical pattern has been observed and
documented by entomologists since the 1940s. In fact, Steffey
reports data documenting these observations will be posted on
the University of Illinois' web site this spring.
Researchers at Pioneer Hi-Bred International, Inc., have been
tracking harvest-time ECB infestation levels on a national basis
since 1997. Their observations also reflect an increase in
infestation levels in 2001, particularly in Illinois, Iowa,
Nebraska, eastern areas of the Dakotas and in southern
Minnesota.
A map of 2001 infestation levels on a county-by-county basis
indicates corn borer pressure was not only widespread, but the
populations levels were much higher, many 70 percent or more, in
most of the counties in 2001 vs. 2000. The same map from 2000
shows ECB pressure over much of the same geography, but the
majority of the infestation levels were at 30 percent or below.
Preparing for 2002
In 1998 and 1999, populations were very low, but the numbers
have increased in 2000 and 2001, indicating a possible upswing
in the ECB cycle. A similar cycle began with high numbers in
1990 and 1991, and then low levels building to highs in 1995
through 1997, depending on geography.
"1997 was our last year of high corn borer populations in
Illinois and across the Corn Belt," Steffey explains. "Odds are
really good that in 2002 numbers of at least first generation
ECB will be higher than 2001 primarily because numbers were high
going into the winter." Winter weather likely has to be
extremely cold or warm to have any significant impact on
overwintering corn borers. The most important factors that
affect ECB in the spring are spring weather conditions and the
presence or absence of parasitoids and pathogens. Ostlie also
reports that the current length of the span between corn borer
peaks in Minnesota is unprecendented.
As human nature kicks in and growers seek a simple answer to the
question of what to do to avoid losses from ECB in 2002, the
guessing game begins again.
"There is no simple answer," echo the experts.
Growers can take their chances and do nothing. They can plan to
scout fields and be prepared to treat if borers reach economic
levels, or they can plant ECB-resistant hybrids. The experts
recommend using ECB-resistant hybrids to manage the risk of
potential yield losses.
"Growers know their level of risk," says Murt McLeod,
entomologist and agronomy research manager for Pioneer in
Windfall, Ind. "They also know their fields and which ones will
be planted early and those that are more prone to corn borer
infestation. I typically recommend growers use resistant hybrids
on a portion of their acres, particularly on the high-yielding
acres."
For example, McLeod explains that an 8 percent yield benefit
where the yield potential is 200 bushel/acre delivers a greater
overall return than that same 8 percent on a 130-bushel-per-acre
field.
"Every grower has a different need for risk management and using
ECB-resistant hybrids is like purchasing an insurance policy,"
Ostlie says. "Every bushel is important, but some growers can
tolerate less fluctuation in yield and need to invest more in
insurance. I definitely think now is a good time for growers to
evaluate their corn borer risk management."
Pioneer Hi-Bred International, Inc., a subsidiary of DuPont, is
the world's leading source of customized solutions for farmers,
livestock producers, and grain and oilseed processors. With
headquarters in Des Moines, Iowa, Pioneer provides advanced
plant genetics, crop protection solutions and quality crop
systems to customers in nearly 70 countries. During 2002, DuPont
is celebrating its 200th year of scientific achievement and
innovation - providing products and services that improve the
lives of people everywhere. Based in Wilmington, Del., DuPont
delivers science-based solutions for markets that make a
difference in people's lives in food and nutrition, health care,
apparel, home and construction, electronics and transportation.
|