Northwest Iowa Crop Update Newsletter by Todd Vagts ISU Extension Crops Specialist Counties Served:  Carroll, Calhoun, Crawford, Ida, Monona, Pocahontas and Sac.
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Volume 2, Number 22

Northwest IA Crop Update, August 19, 2002
(Word Document)

In this issue 
Western Research Farm Field Day
Determine when to harvest corn for silage
Hail damage assessment on reproductive stage corn and soybean
Reduce harvest losses in lodged corn
Bean Leaf Beetle control

Introduction

The Iowa State University Western Research and Demonstration Farm will host its annual fall livestock and forage field day on Tuesday afternoon, August 27.  Degree day accumulation slowed last week, but should pick up slightly again this week accompanied by a chance for rain showers throughout the week.  Harvest of corn for silage should be beginning soon, pay attention to the milk line to determine when to harvest.  Storms last week banged up some area crops with hail, use the listed guides to help asses damage.  Continue to monitor Bean Leaf Beetle populations through this week.

Western Research and Demonstration Farm Livestock and Forage Field Day

Please plan to attend the Iowa State University Western Research and Demonstration Farm

Livestock and Forage Field Day on Tuesday, August 27, 2002 - Castana, Iowa, Time 1:00 – 5:00 p.m.

The afternoon sessions will highlight research at the farm addressing current and future livestock and forage issues.  Location:  The Livestock and forage Field Day will be held at the Western Research and Demonstration Farm, Located four miles east of Castana on county highway E34

Weather
It appears the weather pattern has shifted to a cooler and wetter pattern.  Cool nights and moderate day temperatures will persist through this week.  Rain showers are forecasted Tuesday through Friday of this week.

Growing Degree Day Accumulation and Crop Development
Corn development is at the R5 (Dent).   Corn development has slowed over the last week due to the cool nights and moderate day temperatures.    The forecasted temperature for the next seven days remains moderate.   The earliest planted corn should be fully dented (Figure 1) and harvest time for silage will be upon us soon.  Degree day accumulation has slowed and is slightly behind last year, but is still above the 12-yr average (Figure 2).  Northwest IA accumulated only 104 degree-days last week but is projected to collect a few more this week at 140 DD.

Corn Silage:  Harvesting corn for silage is on the minds of many producers.  Predicting when to begin harvest can be a challenging task.  Corn silage that is too wet will yield less, result in silo seepage and produce sour tasting silage resulting in lower intake by livestock.  If corn silage is too dry then yield is often reduced, heat damage and mold more easily develops in the silo because fermentation is inadequate, and the silage has lower protein and digestibility.  Harvest moisture also depends on the storage structure.

Table 1 lists the recommended harvest moisture for different storage facilities.  Detailed information on harvesting corn for silage can be accessed at the following web site: http://www.uwex.edu/ces/crops/uwforage/Silage.htm

The following in-season guidelines can be used to predict corn silage harvest date:

·        Note hybrid maturity and planting date of fields intended for silage.

·        Note silking date. Half milk of the kernels will typically occur about 42 to 47 days after silking.

·        Once kernel milkline begins to move, measure moisture of fields intended to be harvested for silage. Use 0.5% per day to predict date when field will be ready for the storage structure.

Source:  Predicting Corn Silage Harvest Dates; August 24, 2000  7(23):140-141.  Joe Lauer, University of Wisconsin Corn Agronomist.

Hail Damage to Reproductive Stage Corn and Soybean:  Recent storms dumped hail on some area corn and soybean fields.  Corn plants will most likely be less affected by defoliation at this calendar date than will be soybeans.  Use the following guides to help make field damage assessments.

Corn (National Corn Handbook)
http://www.extension.iastate.edu/Publications/NCH1.pdf

Soybean (Univ of Nebraska)
http://www.ianr.unl.edu/pubs/fieldcrops/g762.htm

Harvesting Storm Damaged Corn:  Early July wind storms flattened many west-central Iowa corn fields just prior to pollination.  Most fields recovered remarkably well by goose-necking and redevelopment of a brace root system.  Pollination and subsequent crop development has progressed without major problems, yet harvest of the goose-necked corn will be a challenge.  Rows will be difficult to follow, ears will be closer to the ground, harvest speed will be reduced and potential field losses may increase.  Depending on fall harvest conditions, stalk rots may develop, plants may fall back to the ground, and ear damage/loss may increase.  Therefore, timing of harvest, proper combine calibration, special header attachments and safety will be of up most importance.  For more detailed information on reducing harvest losses, go to the following web address:  http://www.extension.iastate.edu/carroll/crops/reducing-harvest-losses.htm

Pest Management
Bean Leaf Beetle (2^nd Generation) has begun or will be emerging soon in area soybean fields.  If 1^st generation population levels exceeded thresholds (for control of 2^nd generation) begin scouting and make treatments as necessary (1st generation threshold for 2nd generation treatment).  Consider defoliation potential of both Grasshopper and BLB when making control decisions.   Use the treatment thresholds from the table found in last week’s newsletter, at the following web address:  http://www.extension.iastate.edu/carroll/crops/vol_2_no_21.htm

(Word Document)