Even in a Drought Late Season Soybean Diseases Can Still Show Up

The 2012 growing season has been one of great variability in terms of the weather and its impact on soybean diseases. Early stand issues were mainly caused by crusted soils due to driving rains or shallow planting into dry soil. Very few soybean disease related questions have been expressed......until now. Last Friday (8/3/12) I walked a field near the Arlington Ag Research Station. It was expressing classic Phytophthora root and stem rot (PRR) symptomology. Yesterday I also received similar questions out of the LaCrosse area. As you examine the symptomatic plants it is important that you differentiate PRR from stem canker as they can easily be confused.

Yesterday I also saw the first report of sudden death syndrome (SDS) from @FS_Mark. Weather conditions will likely limit the severity of SDS statewide however this pathogen was confirmed north of Eau Claire in 2010 so vigilance in those areas that have  received rainfall is important.  As always  make sure that the disease identification is correct for SDS, since foliar symptoms are similar to brown stem rot (BSR). In particular, make sure to examine the whole plant, including stems (looking for internal browning due to BSR) and roots (looking for a root rot and also a bluish hue that is the fungus of SDS). Do not just rely on the foliar symptoms to verify your diagnosis of either disease.


Lastly, in spite of the heat during flowering across the state, we will still see white mold somewhere in the state. This is not necessarily a surprise as we do find the disease each growing season. Based on our current observations and reports though, it appears that the disease intensity will be low, although variation to the soybean variety is be evident.

WI Soybean Yield Contest Entry Deadline Extended to 8/31/12

Drought conditions across Southern WI had dampened grower enthusiasm to enter the WI Soybean Yield Contest. Recent rainfalls, promising forecasts and rapid soybean recovery has again piqued grower interest. To facilitate this interest we are extending the entry due date to August 31st to enter the contest.  Below please find links for entry forms and rules. Good Luck!!!

2012 Wisconsin Soybean Yield Contest Rules

 2012 Wisconsin Soybean Yield Contest Entry Form

Getting Additional Forage This Fall

Dan Undersander and Shawn Conley

Some farmers need additional forage and want to plant a second crop following wheat or corn taken early for silage due to drought.  As of July 15, the best option is to wait until after August 1, and then consider planting oats with or without peas.

While corn may yield as well as any other crop, it is more expensive to plant and will need a frost to dry down the forage sufficiently for ensiling.  Sorghum-sudangrass, sudangrass and millet require 80 degree or higher temperatures for significant growth.  Hot as it may seem now, those temperatures are not likely to occur on a daily basis after Sept 1.  So little fall growth will occur and yield will be low.

Oats, planted the first week of August can be expected to produce 2.5 to 3 t/a dry matter in an average year.  Other small grains will generally produce about half as much since they do not put out a stem.  Adding 20 lb/a peas to the oats will increase palatability but will not affect yield. 

Coblentz, USDA Dairy Forage Research Center, found that a late-maturing forage cultivar (ForagePlus) produced maximum annual yields ranging from 2 to 3.5 t DM/a.  Because the forage cultivar matured slowly it was better able to respond to sometimes erratic late-summer precipitation. These types mature later and produce more tonnage of quality forage.  If seed of a forage type is not available, plant a late maturing oat variety.  After the first week of August use of a forage type oat will provide less advantage and grain-type cultivars often may be better management choices.

The fall planted oat is higher in forage quality than spring planted oats.  Research at the University of Wisconsin by Albrecht found that maturation of summer-sown (August) oats was delayed, resulting in 10 to 15% less neutral detergent fiber (NDF), 18% greater digestibility, and 250% more water soluble carbohydrate than spring-sown oat.

The recommendation would be to plant 1.5 to 2 bu oats/acre (with or without peas).  Soil test to determine if sufficient residual nitrogen remains for the oat crop following the drought-reduced corn crop.  If not, fertilize with 60 to 70 lb nitrogen per acre at planting.  It is also important to check for any herbicide plant back restrictions prior to planting the oat or oat/pea mixture.  Planting should occur during the first week of August as earlier planting will result in earlier maturation and reduced yield. Selection of a forage-type cultivar likely will result in superior yield and nutritive value for planting dates as late as the first week of August.

Figure 1. Concentrations of total digestible nutrients (TDN) from oat forages planted on August 1 and harvested on five dates throughout the fall at Marshfield, WI (Coblentz et al., 2012).

Deadline Approaching for Entering the 2012 Wisconsin Soybean Association Yield Contest

Drought conditions in the Southern part of WI coupled with record high temperatures statewide has dampened the excitement of last year’s yield contest where Joe Zenz from Lancaster topped the 2011 Non-Irrigated WI Soybean Yield contest at 92.8 bu a^-1 planting Asgrow 2403. Jason Weigel from S+W Farms LLC, Platteville placed second at 89.7 bu a^-1 with Dairyland DSR-2770/RR and last year’s winner Rick Devoe from RnK Devoe Farms, Monroe placed third at 87.4 bu per a^-1 with Pioneer 92Y51.  

If we do get into a rainfall pattern there is still significant yield to be gained so as a friendly reminder:

• The deadline to enter the 2012 WI Soybean Yield Contest is 8/1/12. 
• The objective of this contest is to encourage the development of new and innovative management practices and to show the importance of using sound cultural practices in WI soybean production. 
• The two major changes to the 2012 contest are that irrigated and dry-land entries are combined and two winners will be selected from each of four geographical districts in the state. 
• Districts are based on long term county soybean yield averages (Image 1 below). 
• For more information please see the contest brochure or review contest rules. Entry forms will be posted shortly on www.coolbean.info.

For more information related to this contest please contact Shawn Conley at spconley@wisc.edu.

Preliminary Wheat Yield Results - Janesville, WI

Preliminary winter wheat yields at our Janesville, WI variety trial site have been averaging 85 bu per acre. Test weights have all been above 60 pounds with moisture ranges of 12 to 13%. The highest plot yield noted so far has been 108 bu per acre.

Late-Season Weed Escapes in Wisconsin Corn and Soybean Fields

The potential increase of glyphosate-resistant weeds is a major threat to corn and soybean production across the Nation.  Integrated Weed Management tactics, including diversified herbicide use, are important components of management to delay the onset of glyphosate resistance.  Identifying geographies that may be most vulnerable to resistance development could help direct attention and pro-active resistance management tactics before wide-scale control failures occur.  To help with this, the University of Wisconsin-Madison Field Crops Weed Science Extension program is asking for your participation in a research study investigating the weed species diversity in Wisconsin Corn and Soybean fields due to reduced atrazine use and subsequent increased use of glyphosate. The purpose of this research is to identify areas in the state where there may be a shift to weeds that are more difficult to control with glyphosate, or where weeds that are resistant to glyphosate may first appear. 

This survey asks questions about target weed species and limited management history information relating to crop production fields. There are two levels of participation in this survey.  The first level simply includes filling out an on-line survey with information from ONLY ONE CROP PRODUCTION FIELD per survey form.  If you are willing to provide information about more than one field, please repeat the survey.  The second level of participation, if you would please participate further, is to allow weed science research staff from the University of Wisconsin-Madison to survey your crop fields for weed escapes in late-summer months. 

We expect the survey to take only 5 to 10 minutes of your time, and we don't anticipate any risks to you.  For fields we scout for weed escapes in the late summer, we will provide a detailed weed scouting report to participants.

You may ask questions about the research at any time by contacting Vince M. Davis at vmdavis@wisc.edu (608) 262-1392 or Ross Recker at rrecker@wisc.edu.  Your participation is completely voluntary.  By completing and electronically submitting this survey, you consent for participating in the first stage of the survey. If you would like to participate in the second stage, and allow UW weed science researcher to scout your production fields, please complete the last question of the survey by providing your contact information.

To complete the survey, please visit: http://www.zoomerang.com/Survey/WEB22FSESTMEKJ

We THANK YOU in advance!  

Vince M. Davis, Extension Weed Scientist and Ross Recker, Graduate Research Assistant

Early Season Water Deficit Stress on Southern WI Soybeans

I went to bed last night hoping this article would not have to be written, but that whopping 0.05 hundredths (or less) of rain we received across much of Southern WI last night forced the issue.  According to data from the 2012 Weather Summary for UW ARS - Arlington and Marshfield WI Locations (compiled by Dr. Joe Lauer) we are tracking over 4 inches behind the 30 year norm at Arlington (precipitation from April 1 to today). A similar trend was occurring at our Marshfield location until recent rainfalls brought us back to near 30 year norms. The implications of this water deficit on soybean are as follows.   

In soybean there are two growth periods for which soil moisture is critical for optimum growth and development: at planting and during the reproductive stages from bloom through pod fill.  The time period from stand establishment to bloom is not as critical.  Drought stress during this time period will often shorten internodes; however yield loss rarely occurs. Luckily most of the WI soybean crop is in the vegetative growth phases though bloom is beginning.  As stated above depleted soil moisture at planting can significantly impact the soybean crop. Therefore if this dry weather pattern continues growers should be very cautions about planting double cropping soybean into dry soil.

In Wisconsin the main reproductive growth in soybean occurs from early July to mid-September.  Soybean in this stage use about 1/4 to 1/3 inches of water per day.  Lack of sufficient water can cause flowers and young pods to abort reducing the number of seeds per plant (Image 1).  Also, soybean plants reduce the size of their leaf pore openings to reduce the loss of water vapor.  This also reduces the intake of carbon dioxide and the manufacturing of photosynthates which slows plant growth.  When normal soil moisture returns, normal growth is resumed.  This ability to reduce metabolic activity allows plants to tolerate dry spells without dying or harming their ability to resume growth when normal moisture returns.

Image 1. Pod abortion in soybean caused by drought stress.

 If a drought does develop and severely affects podset and seed fill, and if livestock feed is needed, soybeans can be harvested as a forage for ensiling.  Highest protein and yields are obtained from soybean harvested at the R6 to R7 growth stage.  Harvesting soybeans for forage between the R1 and R5 stage will result in very high quality silage, but dry matter yields will be reduced significantly.  Forage quality will be reduced from R5 soybean forward if a conditioning process is used during harvest.  Conditioning will cause significant seed shattering. 

 References:

Managing Drought-Stressed Soybeans in the Southeast.  North Carolina Cooperative Extension Service. 1999. 

Virginia Soybean Update. Virginia Agricultural Experiment Station. Volume 2, No. 4, July 1999.