July 7, 2005
Soybean aphids are now being
found in EC Iowa in some soybean fields, especially in the northern part of the
area. A few fields have been sprayed, but aphid numbers have been very low so
far in most fields where they have been found. Aphid reproduction is greatest
during dry, cool weather, so the current weather may increase aphid numbers in
areas that have missed the rains. Brian Lang has monitored aphid numbers during
the last four years in NE Iowa. Although the numbers are higher this year than
last, they are still much lower than they were in 2003. You can see his counts
in the last ICM Newsletter at http://www.ipm.iastate.edu/ipm/icm/2005/6-27/aphids.html.
The economic threshold is considered to be 250 aphids per plant. For more
information on soybean aphids see http://www.ent.iastate.edu/soybeanaphid/.
Asian Soybean Rust
The first observation of
soybean rust in soybeans planted this year was made recently in southern Alabama and Florida. In both cases the rust was found in sentinel plots. Despite
extensive scouting for the disease, there have been no reports further north.
Brown spot can now be found in many soybean fields in SE Iowa. Like soybean
rust it also first shows up on the lowest leaves. You need to look for pustules
with a 15X or 20X magnifier in order to differentiate between brown spot and
soybean rust. Pocket magnifiers can be found at the same 2 sources given above
for sweep nets. If you think you see a pustule, make sure it is not a piece of
dirt. It is not likely that we will see soybean rust in Iowa until it is
confirmed further north in the U.S. To see the latest visit http://sbrusa.net/.
FOR YOUR CALENDAR
July 8, Ag Professional
Tour, NE ISU Research Farm, Nashua.
Program runs 9:30 to Noon. We will discuss "hot" topics at the time, including the latest developments of soybean aphid, rust, more results from the alfalfa S fertilization trials, herbicides trials, and any other observations and experiences from the group. A $10 registration fee will be charged at the door, $25 for CCA credits (2.5 CCA credits available). Pre-registration is not required.
July 12, Grazing Field Day, Andrew Jackson Demonstration Farm, Andrew.
Starts at 6:30. Discuss stockers and cow-calf; new forage seedings for pasture, and grazing corn. Directions: N of Andrew in Jackson County on Hwy 62 to County Rd Y-61.
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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