The significant aphid
infestation reported in a field near Mediapolis caused quite a stir, but it
appears that it was a single odd occurrence. Other fields in the area also had
some soybean aphids, but only a few per plant and only a few plants with aphids
per field. There have been other scattered reports of aphids across the state,
but most have been at extremely low numbers and in just a few spots in the
fields. Some of the aphid reports have turned out to be thrips,
which are common in soybeans, but usually not an economic problem.
Some are asking about including an insecticide with the Roundup
application just in case the aphids or bean leaf beetles become a problem
later. Now is not a good time for spraying for bean leaf beetles since we are
between generations. Spraying for aphids when very few aphids are present may
not only be a waste of money but might actually make the aphid problem worse by
killing off the beneficials that are keeping the
aphid population in check. The working economic threshold for aphids is 250 per
Several soybean fields in the area have showed some injury problems
from flumioxazin (Valor, Gangster). In a few cases
the fields had to be replanted. Some of the injured soybeans were showing
symptoms similar to dicamba injury (cupped leaves).
For more information see the following article by Bob Hartzler:
Soybean Damping Off
Some of the damping off of soybeans that is now occurring in the area
may be due to Phytophthora rather than Pythium. If the soybeans are replanted, variety selection
is important if the damping off is being caused by Phytophthora.
Many Phytophthora resistant varieties use the
"Rps1K" gene, which is not effective on several new races. If this is
what is present in the affected variety, the replanted variety should contain
the Rps-6 gene instead. See X.B.'s recent article for
more information: http://www.ipm.iastate.edu/ipm/icm/2004/6-21-2004/phytop.html.
How Late Can Nitrogen Be Applied to Corn?
The wet weather has
delayed the N application in some corn fields and has resulted in nitrogen
losses in other fields where the soil has been saturated. Corn can benefit to N
applications even as late as tasseling if the soil is
deficient. If no nitrogen has been applied or the corn is
showing N deficiency symptoms, about 60-80 lb/A could be dribbled between the
rows. Lower amounts might be sufficient if N has already been applied
and corn is somewhat pale in color but not severely deficient. The July 2, 2001
ICM Newsletter has more information at http://www.ipm.iastate.edu/ipm/icm/2001/7-2-2001/nottoolate.html
EVENTS IN THE NEAR FUTURE TO GET ON YOUR CALENDAR
24 NE Iowa Spring Field Day, Nashua Lunch and Static Displays 12:00
1:30PM ; and wagon tours from 1:30 4:30 PM.
June 28 Pasture Walk - Benton County 6:00 p.m. Don Newton farm, corner of 18th Ave. Dr and 75th St. Dr. north of
Blairstown. Discussion will focus on typical Iowa creek pasture concerns; weed control, improving
stands, rotational grazing options. Free meal at .
June 29 Soybean Rust Update, Johnson County Extension Office, Iowa City 9:00
a.m. to noon This morning meeting will be a multi-state distance education program that
will bring together the most knowledgeable people on the subject in the United
States to provide insights on the status of the disease, most likely scenarios
for it to move to North America, distinguishing between soybean rust and other
leaf diseases, and the process that is in place to monitor for the disease and
confirm its presence when it arrives. This meeting will NOT train CCAs to be first detectors. The fee is $10 for non-CCAs and $35 for CCAs attending
for credit. Please send me an e-mail note by June 28 if you plan to attend.
July 6 Pasture Walk - - IowaCounty Amana Farms, pasture on the north
edge of the visitors center, meet at the visitor center/RV park in Amana.
Tall fescue is an increasing pasture problem in eastern Iowa. This pasture walk will focus on identifying
tall fescue, managing fescue pastures and animals grazing fescue, featuring Dan
Morrical, ISU Extension Sheep/Forage Specialist.
July 8 First Detector Training For Asian Soybean Rust - Montgomery Hall, JohnsonCounty Fairgrounds
This program is for Certified Crop
Advisors and Certified Professional Agronomists to train them to become
"first detectors" to learn how to identify soybean rust. There is no
pre-registration for this meeting. The fee is $20 (made out to ISU). CCA
credits are available.