C.O.R.N. Newsletter 2012-26

Dates Covered: 
August 14, 2012 - August 20, 2012
Editor: 
Rob Leeds

Weather Forecast: Slightly below normal temperatures and rainfall

Near to slight below normal temperatures and rainfall are forecast through the remainder of August. Any drought conditions will continue a slow improvement. Normal rainfall for the period is near 1.5 inches with normal highs near 80 and normal lows near 60. Rainfall is forecast to average 1-1.5 inches with the range being 0.5 to 2 inches with the state average of 1.25 inches for the rest of the month for Ohio.

Looking back at the January and February outlooks, the NWS OHRFC called for a hot and dry start to summer ending a bit cooler and wetter than normal. This turns out to be almost exactly what is happening.
 

Late Season Insect Expectations

Late Season Insect Expectations

With the growing season coming to an end, there are a few insect pests that we should discuss, including which ones are still a concern and those of interest.  The main insect that growers should continue to monitor are bean leaf beetles on soybean, especially in fields that remain green into September.  The final adult generation will feed on pods and seeds, resulting in both fewer seeds as well as quality issues.    Beetles will tend to go to late maturing fields to feed prior to overwintering, and often cause more damage to seeds than expected.  See fact sheet http://ohioline.osu.edu/ent-fact/pdf/0023.pdf for information on pod feeding by bean leaf beetles.  This is probably a more widespread problem than realized.

Another pest to watch out for, albeit we do NOT expect it to be a concern, is the brown marmorated stink bug.  This is a potentially new crop pest in Ohio that so far has not caused many problems except for homeowners and renters in the fall.  However, we expect it to sooner or later begin feeding on soybeans in late summer.  Growers might want to monitor their fields, especially along field edges nearest wooded areas, for the presence of this new pest.  See fact sheet http://entomology.osu.edu/ag/images/Marmorated_Stink_Bug.pdf for more information.  Anyone finding the brown marmorated stink bug in their soybeans are asked to let us know about it by sending an email to hammond.5@osu.edu

As we predicted, this past summer was a “low” soybean aphid year (C.O.R.N. Newsletter 2012-08, April 10-16, 2012), with very few aphids being found.  If things hold true like in past years, we will begin to see some aphids on soybeans over the coming weeks.   However, these will NOT reach levels to cause concern, especially at the late growth stages that soybeans will be at.  But it will be these aphids that will produce the eggs that will later be found on buckthorn that will overwinter.  We would point out that trying to control any late occurring soybean aphids to prevent an overwintering population will NOT work; so do NOT apply insecticide sprays for these aphids.  We will monitor the buckthorn this coming fall, and more importantly, remind growers to keep a watch for aphids next summer.

Finally, Ohio is now experiencing cooler and wetter conditions, both of which appear to be causing twospotted spider mite populations on soybeans to diminish.  Before making any further treatments for mite control, definitely check to see if most mites are still alive.  We think you will find that most mite numbers have finally dropped.

Survey on Postemergence glyphosate management for control of giant ragweed, we need your input and Palmer amaranth arrives in Ohio

OSU weed scientists are collecting information on the management of postemergence glyphosate applications in no-till Roundup Ready soybeans, where giant ragweed is a primary weed target.  The survey found at the following link is brief (10 questions) and completely anonymous:  http://www.surveymonkey.com/s/SFRKY8W.   It asks for information on the rate, frequency and timing of POST glyphosate applications.  The information we collect from this survey will help us to determine the type of education we need to conduct to improve control of giant ragweed in soybeans.  Thanks in advance for your participation.

The dreaded Palmer amaranth arrives in Ohio

We have plenty of glyphosate-resistant weed populations in Ohio, and resistance currently is know to occur in four weed species here – marestail (horseweed), giant ragweed, common ragweed, and waterhemp.  However, our resistance problems have appeared to be overall less severe than in the southern United States, where the now widespread occurrence of Palmer amaranth has had a substantial impact on crop yields and profitability of cotton and soybean growers.  Palmer amaranth is in the pigweed (Amaranthus) family, and has been fairly accurately characterized as “pigweed on steroids”.  In addition to the glyphosate resistance, this weed’s rapid growth, large size, extended duration of emergence, prolific seed production, and general tolerance of many POST herbicides makes it a much more formidable weed to deal with than the pigweed species we have here in Ohio.  The populations of glyphosate-resistant waterhemp that can be found in western Ohio would be the closest we have to Palmer amaranth in terms of overall characteristics, but Palmer amaranth has overall more potential to reduce yield if not controlled.

We have at this point confirmed the presence of Palmer amaranth in one large field near Portsmouth, Ohio, and this population is resistant to both glyphosate and ALS inhibitors.  As far as we can tell, the source of this population may have been a CREP/wildlife type seeding, where the seed of the desirable species was apparently contaminated with Palmer amaranth seed.  There are several other suspect sites in Ohio, which we are in the process of investigating.  There are also new infestations of Palmer amaranth in Michigan and Indiana, and the source of these appears to be contaminated cottonseed shipped from the southern US for use as animal feed here in the Midwest.  Manure from these animal operations was spread on fields, and the Palmer amaranth then became established.  We will provide more information on this weed in the future, but there are some major steps that need to be taken right now to prevent additional new infestations.  The overall goal here is to avoid spreading manure on crop fields from animal operations where cottonseed was used as feed.  This manure is likely to contain Palmer amaranth and should not be spread on crop fields.  Where the manure comes from an animal operation other then your own, be sure to find out whether cottonseed was used as feed before agreeing to take any manure.  This is one of those rare occasions where we have enough information to hopefully prevent additional infestations of an extremely aggressive weed, and there could be serious long-term consequences for farm profitability for failing to do so.

Survival of Soybean Rhizobia Cells in Soil

Survival of Soybean Rhizobia Cells in Soil

The dry weather of 2012 has given cause for worry about many areas of crop production. On a recent trip to Ukraine, it became obvious that high soil temperatures and dry surface conditions there have greatly reduced rhizobia populations. This is a country where soybeans are only recently being established, first year soybeans even with inoculants applied are suffering from lack of nitrogen due to the lack of rhizobia development. While we in Ohio have a long relationship with soybean and rhizobia, conditions this year may lead to concerns for next year.

Soybean rhizobia bacterial cells survive best when they are in a moist soil environment and an ambient soil temperature of 40-80 degrees F.  The drought throughout the Ohio in 2012 has resulted in the top six inches of soil becoming extremely dry and very hot in many fields.  Either a very dry soil environment or a very hot soil environment causes the rapid death of rhizobia cells and the combination is lethal.  Therefore, we would expect a reduction in the population of residual soil rhizobia cells in many Midwestern soybean fields in 2012 due to those soil conditions.  Although many cells will survive the extreme environmental conditions, those cells will have evolved into survival mode and will have lost much of their potential to provide nitrogen to soybean plants in 2013. That means the surviving rhizobia population will likely be less productive next year than in previous years. That reduced productivity should translate into increased yield responses to inoculating soybeans and other legume seeds in the spring of 2013. 

Wheat Performance Results for 15-Inch Row Spacing Available Online

Performance results for wheat grown in 15-inch row spacing are available online at: http://oardc.osu.edu/wheattrials/Ohio_Wide_Row_Wheat_Summary_2012.pdf

The varieties selected for evaluation in 2012 were in the top half of the 2011 Ohio Wheat Performance Test.  In 2012, the varieties averaged 106 bushels/acre with a range of 98 to 112 bushels/acre across both locations.  Table 1 gives results for the Crawford and Wayne County locations.  Table 2 gives two-year summary results for the Crawford County location.  For each variety, yield at 13.5% moisture, test weight, percent moisture, spring stand, lodging, height, and heading date are given.  Heading date was the average calendar day of the year on which 50% of the heads were completely emerged (i.e., Day 136 = May 15).   Seeding rate was 25 seeds per foot of row for all varieties. 

It should be noted that this is a stand-alone test and comparisons should not be made with the results published at 7.5-inch row spacing in the Ohio Wheat Performance Test.  This information provides wheat performance information for growers who are interested in growing soft winter wheat in 15-inch row spacing to utilize precision planting implements or Modify Relay Intercrop (MRI) soybeans with wheat.  In a MRI system, soybeans are planted between wheat rows when wheat is headed (Feekes 10 growth stage).  For more information about wheat row spacing and MRI see this C.O.R.N. newsletter article from last year:  http://corn.osu.edu/newsletters/2011/2011-27/wheat-variety-yield-in-15-inch-rows.

 

Aspergillus Ear Rot and Aflatoxins

Most of our corn this year has experienced extremely hot, dry conditions and as a result grain development has been severely hampered. In addition, such drought-like conditions have had several producers concerned about Aspergillus ear rot and aflatoxin contamination of grain. Although I have not yet received reports of Aspergillus ear rot and aflatoxin in Ohio, these concerns are understandable and justified. Normally, aflatoxin contamination of corn is not a major issue in Ohio, but the dry conditions experienced across the state could lead to such a problem this year. Drought-stressed corn is more susceptible to infection by Aspergillus flavus, an ear rot fungus that produces a very potent group of carcinogenic (cancer-causing) toxins called aflatoxins. However, the fungus can infect grain and produce aflatoxin under a wide range of conditions: temperature between 54 and 108F; kernel moisture between 15-25% and relative humidity above 80%. But it should be noted that although Aspergillus ear rot is a good indicator of potential aflatoxin contamination, there are no guarantees that: 1) moldy ears will be contaminated with aflatoxins; 2) ears without visual signs of fungal infection will be free of aflatoxins, and 3) the amount of Aspergillus ear rot will provide an accurate measure of the levels of aflatoxin contamination. In addition to weather conditions, the levels of ear rot development and toxin contamination depend of the strain of the fungus, with some members of the Aspergillus flavus group being capable of producing more or less toxins than others.       

Producers should start checking for Aspergillus ear rots by stripping back the husks and examining the ears of 80-100 plants sampled from across the entire field for a yellow-green or gray-green mold. Since not all ear rots are associated with mycotoxin contamination, it is important to properly identify ear rots before harvest in order to determine if mycotoxin will be a concern and to make adequate marketing and storage decisions. Aspergillus ear rot tends to be more severe in insect- or bird-damaged fields or sections of a field and is much easier to identify in the field than in harvested grain. Samples from suspect fields should be sent to an approved laboratory for testing to determine whether aflatoxins are present and whether they exceed thresholds established by the U.S. Food and Drug Administration. More information on aflatoxin testing and FDA thresholds are available at:

http://www.rma.usda.gov/fields/il_rso/2012/aflatoxin.pdf

http://www.fda.gov/Food/GuidanceComplianceRegulatoryInformation/GuidanceDocuments/ChemicalContaminantsandPesticides/ucm077969.htm#afla

More Yields from Your Fields Agriculture Field Day- August 28

Because fertilizer used in crop production has been identified as one of the sources of nutrients transported to Ohio lakes and rivers via sedimentation, runoff and tile discharge, a new crop nutrient management approach, the 4R Nutrient Stewardship Program, will be shared via innovative approaches to crop nutrient placement with equipment demonstrations and displays from John Deere, Krause, Case IH, Great Plains Equipment and Hiniker Equipment.  Also, there will be conservation tillage and strip till demonstrations (weather permitting); precision ag technology and drainage water management.   The field day will be held at the Ron Schroeder farm located at 7042 Crestline Rd., Crestline, Ohio on August 28, 2012 from 2-5 PM.  The program is sponsored by OSU Extension, The Crawford Soil & Water Conservation District, Sunrise Cooperative Crestline and the Sandusky River Watershed Coalition.

 

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About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.