Corn for silage
Predicting silage harvest dates
Past the point of return on soybean aphids
Soybean SDS
Castana Field Day
Crop update live

Introduction
The ten-day forecasted warm temperatures should continue rapid crop progress toward maturity.  Preparations for silage harvest should be on the top of the list.  Grain harvest will not be far behind.  Soybeans continue to harbor some pests, spider mites, SDS, bean leaf beetles and even some Bacterial Pustule (Humboldt and Webster counties) can be found in area fields.  Soybean aphids can also be found, but most fields are most likely far enough along in development that a return to treatment will most likely not be seen.  If you haven’t yet attended a Crop Update Live session, be sure to attend this week’s program.

Weather information
Growing Degree Day  West-central IA continues to rack up the degree days with last week’s 145 DD accumulation, 14% greater than normal for the week.  This week’s forecasted accumulation (138) will also be above normal.  Notice the number for 2004, this was the first week of the early fall warming trend that occurred last year into September.  Accumulation and predicted plant phenology stages are shown in Table 1 and Figure 1 and is forecasted through August 28.  More detailed degree-day accumulations by planting date can be obtained at this URL:  http://www.extension.iastate.edu/nwcrops/degree-days-2005.htm

Table 1.  Degree-Day Weekly Accumulation
	2005	2004	2003	14-Yr Ave
Aug 15-21	145	90	189	127
Forcasted Aug 22-28	138	142	174	131

Crop Management
Corn Development  Most corn in the area is denting with the milk line advancing down the kernel.  Corn harvest for silage will be occurring soon.  Information from a MN Extension newsletter (http://www.extension.umn.edu/cropenews/Regnews/SEAugust272004.pdf) suggests that corn requires 194 degree-days to advance from full dent to ½ milk line and 176 degree-days to advance from ½ milk line to black layer (physiological maturity). 

Corn

Silage:   Predicting when to begin harvest can be a challenging task.  Corn silage that is too wet will yield less, will have silo seepage and will 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 2. Kernel milk stage "trigger" to begin sampling for various silage structures.
Silo Structure	Moisture content for Ensiling	Kernel Milk Stage “trigger”
	%	%
Horizontal Bunker	70 – 65	80
Bag	70 to 60	80
Upright Concrete Stave	65 to 60	60
Upright Oxygen Limiting	60 to 50	40
*"trigger": kernel milk stage to begin checking silage moisture *Silage moisture decreases at an average rate of 0.5% per day during September

Table 2 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

Corn Silage Harvest typically occurs between ¼ to ½ milk line, which under normal conditions will occur from 42 to 47 days post pollination.  According to projections based on the “Projected Phenology Events” table, plan silage harvest to begin from August 26 to September 05 based on silking dates of July 15 – 25.

Projected Phenology Events From Silk Date
Silk Date	Dent	1/2 Milk	Black Layer
Days from silk	35-42	42-47	55-60
15-Jul	19-Aug	26-Aug	08-Sep
20-Jul	24-Aug	31-Aug	13-Sep
25-Jul	29-Aug	05-Sep	18-Sep

Pricing forage in the field?  Use this ISU Extension fact sheet found at this web URL:  http://www.extension.iastate.edu/agdm/crops/pdf/a1-65.pdf

Pest Management
Soybean Aphid  Most soybean fields are most likely past the point (R5.5 to R6) of return to an insecticide application.  In the past, aphid populations tend to decrease or entirely disappear near the end of August.

Sudden Death Syndrome in soybeans has been found in central and north-central Iowa.  Early planted fields are at highest risk for infection.  X.B. Yang (ISU Extension Pathologist) describes symptoms as scattered yellow spots between leaf veins. These spots eventually coalesce to form brown streaks between the veins (interveinal necrosis). Only the mid vein and major lateral veins remain green. Leaflets drop eventually.  Diseased plants have deteriorated taproots and lateral roots. The root cortex is light gray to brown, and the discoloration may extend up into the stem 2 inches above ground. Sometimes bluish fungal colonies can be seen on the root if soil moisture is high.  SDS can spread rapidly throughout a field, detection and positive I.D. is essential to protect soybean yield and profitability.  Once a field has been identified with infection of SDS, select SDS tolerant varieties in subsequent years.  No resistance to this disease is available in any soybean varieties. 

Crop Update Live
Join me in the “Crop Update Live” web meeting to be held on Friday morning at 7:30 am.  I will review and update crop and pest management information presented in this week’s newsletter.  Click on this link http://breeze.extension.iastate.edu/r84713623/  Friday morning to join the meting.  To view a recording of this or past meetings, browse to the Crop Update Live webpage

Fall Livestock and Crops Field Day
The Iowa State University Western Research and Demonstration Farm near Castana, IA will be hosting its annual fall livestock and crops field day on Thursday, August 25, from 1 – 3:30 pm.  Topics covered at the field day include:  Swine Welfare, Animal ID, Producers Role in Meat Quality, New Value Added Meat Cuts, What has happened with aphids and rust,  Solid Waste Settling March ’06 Compliance and Results of feeding Condensed Corn Distiller Soluables.  For more information contact the Monona County extension office at 712-423-2175