June 1, 2004
WET WEATHER WOESAlthough we have escaped much of the torrential rains of NE Iowa, the continued rainy weather is also having an impact in EC Iowa. Some concerns:
Flooding, ponding, and saturated soils can result in
significant losses of soil nitrogen through the processes of
and leaching of nitrate N. Significant loss of soil N will cause
deficiencies and possible additional yield loss. Research in
wetter regions of the cornbelt has demonstrated that in May and June, 4 to
of soil nitrate can be lost each day a soil is saturated.
Some may be needing to change their weed control strategies in corn. Marksman and higher rates of Banvel and Clarity (greater than 8 oz/A) should not be applied if corn is greater than 8 inches tall. For a review of maximum corn sizes and weed sizes for various corn herbicides, see the May 31, 2004 ICM Newsletter at http://www.ipm.iastate.edu/ipm/icm/2004/5-31-2004/weedsinlatecorn.html.
There are still a number of soybean fields to be planted in the area. On average, soybeans planted in early June in central and southern Iowa have yielded about 10% less than those planted in early May. The yield potential does drop more rapidly after early June. Stick with an adapted full season variety through June. A good source of information on soybeans is "Soybean Replant Decisions" (Pm-1851) at http://www.extension.iastate.edu/Publications/PM1851.pdf.
Stalk borer migration from
grassy areas to adjacent corn plants begins at about 1,300 Growing Degree
(GDD) Base 41. As of the end of the day on May 31, the GDD Base 41
about 1250 in Cedar Rapids and 1300 in Davenport. One way to manage the
borers is to spray an insecticide along field edges and waterways during
migration. See pages 81 - 82 of the May 29, 2000 ICM Newsletter or http://www.ipm.iastate.edu/ipm/icm/2000/5-29-2000/stalkincorn.html
for scouting and management details. A tracking of GDD in the
to Dubuque area is at http://www.extension.iastate.edu/Pages/eccrops/stalkborer.html.
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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