C.O.R.N. Newsletter 2010-38

Dates Covered: 
November 9, 2010 - November 23, 2010
Editor: 
Greg LaBarge

Resist the Temptation to Apply 2,4-D to Emerged Wheat in Fall

In our research, the combination of tribenuron and dicamba has been one of the most effective treatments for control of dandelions.  It may be possible to use a combination of dicamba and tribenuron/thifensulfuron premix instead, but thifensulfuron has little activity on dandelion.  Using the premix results in a lower rate of tribenuron, which can reduce dandelion control.  While the mixtures listed above provide broad-spectrum control, control of ALS-resistant marestail is one of the probable weaknesses.  The low rates of dicamba or metribuzin that are labeled for use in these mixtures are not likely to be consistently effective for control of ALS-resistant marestail, although the 4 oz/a rate of dicamba may control very small marestail plants. Huskie may therefore be one of the most effective fall-applied options for control of emerged ALS-resistant marestail populations, and it evidently provides some residual activity also.

We receive many questions about the safety of 2,4-D applications, alone or in combination with other herbicides, to emerged wheat in the fall.  We recommend avoiding this use of 2,4-D based on the following:

  • we have observed yield reduction from use of 2,4-D on emerged wheat in the fall in three of the four studies we have conducted on this topic.  We applied 2,4-D alone in one of these three studies, and a premix of 2,4-D and dicamba in the other two studies.  The yield loss from 2,4-D treatments ranged from 11 to 20% compared with a range of other treatments, which included dicamba applied alone or in combination with Express, Harmony Extra, Starane, and Stinger. 

  • Fall application of a mixture of Peak and 2,4-D was recommended by a manufacturer and used several years ago in northwest Ohio and southern Michigan.  This treatment cause considerable injury and yield loss in some wheat fields.

  • Labels for 2,4-D products, including premixes of dicamba and 2,4-D (Brash, Weedmaster, etc), either do not recommend application in the fall, or indicate that the user must be willing to accept the risk of crop injury (manufacturer has no liability).

The labels for the 2,4-D/dicamba premix products state that application in the fall should occur after wheat has started to tiller, and some growers using 2,4-D in the fall have told us that they do wait until after tillering to apply.  The stage of the wheat plant may have some influence on the potential for injury from fall-applied 2,4-D, but we do not have research-based information with which to make an informed recommendation.  What’s interesting about this is that 2,4-D is usually extremely safe on wheat when applied in the spring. We have been unable to cause yield loss in spring when applied before the early boot stage (note – some 2,4-D labels specify that application must occur before jointing).

The risk of an 11 to 20% yield loss is enough for us to recommend avoiding use of 2,4-D in the fall, but it might be helpful to apply some simple “weed science” economics.  First, wheat is currently worth a lot - $7 per bushel or so, which makes an average Ohio wheat yield (60 bu/A) worth $420.  We’ll assume an average of 15% yield loss where 2,4-D is used in the fall, which is a loss of 9 bu/A or $63/A.  Assuming you are lucky enough to get 90 bu/A wheat, this loss jumps to about 13 bu/A or $94.  The difference in cost between 2,4-D (0.5 lb/A) and either tribenuron + dicamba (0.4 oz + 4 oz) or Huskie (13.5 oz) is about $9/A.  There is essentially no difference in cost between using 2,4-D (1 pt) and either dicamba (4 oz) or metribuzin (2 oz) in a mixture with tribenuron.  To summarize, using 2,4-D instead of dicamba means trying to save somewhere between nothing and $9/A, at the risk of losing about $60 to $90 per acre in income at current wheat prices. 

Restructured and Updated OSU Weed Management Website

Summary and Status of Western Bean Cutworm in OhioWBCW Larvae

Summary and Status of Western Bean Cutworm in Ohio

2010 WBCW Map

Our best management tactic remains monitoring for adults and scouting corn fields for eggs and larvae.  While transgenic varieties with Cry1F (Herculex brand) are effective against western bean cutworm, this product does not provide 100% control like European corn borer.  Furthermore, since we have not seen economic damage in Ohio, producers may not recover the input cost of the Bt trait at least until economic damage is reported.  For a complete updated map of the 2010 season, as well as maps from previous years, please go to our website: http://entomology.osu.edu/ag/.

Soybean Aphid UpdateSoybean Aphid Update

Soybean Aphid Update

What we are saying is that we expect Ohio to continue its two year cycle of very few if any aphids being found followed by low to moderate to even high populations somewhere in the state.  However, it is impossible to predict which regions of Ohio, if any, will experience outbreak conditions.  There are many factors that will determine this, including environmental weather conditions (temperatures, rainfall, etc.) to the presence and effectiveness of biological control agents such as predators, parasitoid, and pathogens. 

At this time, growers should just be aware that scouting for aphids will probably be more important next summer during July and early August.   There is nothing to suggest that any additional measures should be taken, including the use of seed treatments specifically for aphid control.   Economic levels of aphids occur in mid-summer in Ohio, and seed treatments will not offer economic benefit in terms of early summer populations, nor greatly impact their numbers later in the summer.  

One activity that growers should consider is skip-row planting which would be of benefit in narrow row soybeans if spraying does become required for soybean aphid, but would also be of benefit for herbicide and if needed, fungicide spraying.  See the following web site and fact sheet for information on skip-row planting http://entomology.osu.edu/ag/images/skip_row.pdf

New Transgenic Corn Product, Optimum Intrasect

Until that time comes, hopefully within a year or so, they have obtained EPA approval and released to the market an intermediate product called Optimum Intrasect which contains two gene proteins, Cry1F and Cry1Ab, for corn borer control (rootworm control is not part of Optimum Intrasect).   Pioneer has obtained EPA approval for the reduction of the refuge for Optimum Intrasect to a 5% block or strip, similar to that of SmartStax, the Monsanto product.  Thus, growers planting Optimum Intrasect can plant a much smaller refuge compared with earlier products.

Request for Help Evaluating the Wheat Head Scab Prediction SystemRequest for Help Evaluating the Wheat Head Scab Prediction System

Request for Help Evaluating the Wheat Head Scab Prediction System

The web-based prediction tools (http://www.wheatscab.psu.edu/riskTool_2010.html)provide daily estimates of disease risk for 25 states east of the Rocky Mountains. This multi-state effort requires considerable resources to maintain, and scientists involved in the project would like to gather some input to justify continued investment of time, computing resources and funds needed to sustain the effort.

If you have used these tools during the 2010 growing season, we would like to hear from you. Please take a few minutes to complete this on-line survey that will help us evaluate, improve, and maintain the system.

The link to the survey is: http://www.hostedsurvey.com/takesurvey.asp?c=2010Us121326

Soybean Diseases in the News

Not a problem in 2010 in the US.  What a difference a year can make.  During 2009 losses were recorded in Mississippi, but in 2010 soybean rust was found in October at very low levels, too late to cause damage.  Basically, soybean rust was frozen out last year as the kudzu (an additional host and overwintering host) was killed back last year through much of south.  The cycle will now repeat itself, how hard a winter will it be in the southern US, how much kudzu will survive and how of it has rust infections will all play a role in assessing next year’s epidemic.  The Southern Kudzu Scouters of Extension specialists are to be thanked for their efforts:  The team at Univ. of Florida at Quincy led by Dr. Jim Marois; Super Kudzu man at University Alabama, Dr. Ed Sikora (I think needs to wear a bullet proof vest based on some of his picture); the traveling team in Mississippi State University led by Dr. Tom Allen;  Louisiana State University Group led by Dr. Clayton Hollier; and finally Dr. Tom Isakeit who really searches year round as the southern tip of Texas starts some late soybeans in November and December.  We greatly appreciate all their efforts, it gives me time to focus on problems that are already in Ohio.  Visit the website to see the final map of the season:  http://sbr.ipmpipe.org/cgi-bin/sbr/public.cgi.  Surveys will hopefully start up again in April 2011.

Fungicide Resistance to Frogeye Leaf Spot

At this point one field in Tennessee has a population of Cercospora sojina which is insensitive (resistant) to strobulurin fungicides.  Headline and Quadris are the two that have been used most often in this particular field.  Basically, this field has had several years in a row of soybeans, which were highly susceptible to frogeye leaf spot.  It took several sprays, but this year the fungicide had very little effect.  The long-term and sole use of the strobulurin fungicides to control this fungal disease was an accident waiting to happen, combined with continuous soybean and the same susceptible variety is the basic recipe for developing fungicide resistance.  This is a good reminder for everyone:  don’t plant the same variety in the same field in back-to-back years if there has been a foliar disease (any disease really).  We now know that the fungus that causes frogeye leaf spot can overwinter in the northern states and so that inoculum that builds up on a susceptible variety will be there ready to infect the next crop.  Combine this with a fungicide that is prone to high selection pressure on the pathogen population and this event is not surprising.  Lesson:  rotate crops, if you have a disease outbreak or have to spray for disease on a field crop – plant something else the following year.  For frogeye leaf spot it is now more important than ever to plant varieties with the Rcs3 gene.

Seed Treatments

There are some products on the list this year and we’ve updated the seed treatment list on the website. Seed treatments are essential for Ohio fields that are poorly drained, have been in continuous soybean production and have experienced replanting.  Fields where Phytophthora stem rot is prevalent, really need the high rate (0.64 fl. oz/cwt) Apron XL (mefenoxam) or 1.5 fl oz/cwt of metalaxyl (Allegiance, MetaStar and several other generics).  There are more and more fields where the P. sojae populations are quite diverse and the Rps genes are no longer effective (includes Rps1c and Rps1k).  In a two year study in Ohio, all resistance packages benefited from the seed treatment (ApronXL at 0.64 fl. oz/cwt) at least one year of the study and highly susceptible varieties benefited both years of the study. http://www.oardc.ohio-state.edu/ohiofieldcropdisease/corn/seed%20treatments%202011.pdf

2010 Ohio Corn Performance Test: An Overview

Environmental conditions varied greatly across Ohio during the 2010 growing season, especially with regard to the amount and distribution of precipitation. Yields were highest at the S. Charleston and Washington CH test sites in the SW region (averaging above 242 bu/A) and lowest at Hoytville in NW Ohio and Beloit in NE Ohio (averaging less than 148 bu/A). At most test sites, rainfall from planting through the mid to late vegetative stages of corn development was above normal. Excessively wet soils in May and June limited early season root development and resulted in shallow root systems. Saturated soil conditions contributed to reduced emergence of some hybrids.  Dry weather conditions combined with above average temperatures persisted from the late vegetative stages through maturity at most sites. Water deficits were especially severe at the Hoytville test site. Test results from Greenville in the SC/WC region and Wooster in the NC/NE region test locations are not reported because of weather related damage.  At Greenville, heavy rains shortly after planting, in combination with late season water stress, resulted in erratic stands that led to highly variable yields.  At Wooster, strong winds associated with a tornado on Sept. 16, destroyed and flattened much of the corn test. At other test sites, water stress was limited by timely rains and adequate soil moisture. In contrast to 2009, high temperatures during grain fill accelerated crop maturation and resulted in much lower than normal grain moisture at harvest. Despite the varying degrees of stress present at most sites, stalk lodging was negligible – averaging no more than 5% at any location. Extensive foliar disease (primarily gray leaf spot and northern corn leaf blight) was evident late in the season at several locations but impact on crop performance appeared to be limited.

Grain yields in the Southwest and West Central region (the S. Charleston and Washington C.H.  locations), averaged across hybrid entries in the early and late trials, were 243 bu/A. Yields in the Northwest region (Van Wert, Hoytville, and Upper Sandusky locations) averaged across hybrid entries in the early and late trials, were nearly 185 bu/A. Yields in the North Central and Northeast region (the Bucyrus and Beloit locations) averaged across hybrid entries in the early and late trials, were 180 bu/A. In addition hybrid yields at Coshocton averaged 212 bu/A.

Tables 1 and 2 provide an overview of 2010 hybrid performance in the early maturity and full season hybrid trials by region. Averages for grain yield and other measures of agronomic performance are indicated for each region. In addition, the range in test sites averages is shown in parentheses. . Complete results are available online at: http://www.ag.ohio-state.edu/~perf/ and http://www.oardc.ohio-state.edu/corntrials/.

Table 1.   A regional overview of the early maturity 2010 Ohio Corn Performance Test.

 

Region

 

Entries

Grain Yield

(Bu/A)

Moisture

(%)

Lodging

(%)

Emergence

(%)

Final Stand

(plants/A)

Test Wt.

(lbs/bu)

SW/WC

72

239

(212-260)

16.6

(14.1-19.7)

0

(0-1)

96

(87-99)

33700

(28400-38900)

59.7

(56.6-63.3)

NW

88

181

(162-204)

16.8

(14.7-19.5)

2

(0-21)

88

(75-97)

30700

(24200-36600)

59.5

(57.1-62.5)

NE/NC

78

181

(163-203)

18.4

(15.3-21.5)

2

(0-13)

92

(79-98)

32400

(25200-38300)

58.0

(55.3-61.3)

 

 

Table 2.  A regional overview of the full season 2010 Ohio Corn Performance Test.

 

Region

 

Entries

Grain Yield

(Bu/A)

Moisture

(%)

Lodging

(%)

Emergence

(%)

Final Stand

(plants/A)

Test Wt.

(lbs/bu)

SW/WC

96

246

(211-265)

18.0

(15.4-20.9)

0

(0-3)

97

(87-100)

34100

(27500-38700)

58.7

(55.6-62.0)

NW

92

191

(168-213)

18.3

(16.5-21.6)

5

(0-28)

89

(74-96)

30600

(23200-35200)

59.0

(55.2-62.8)

NE/NC

65

181

(159-215)

20.4

(16.6-24.9)

2

(0-18)

93

(79-99)

33100

(26900-37800)

57.5

(54.3-61.6)

As you peruse this year’s corn test results, it’s important to keep the following in mind. Confidence in test results increases with the number of years and the number of locations in which the hybrid was tested. Data from a single test site should be avoided, especially if the site was characterized by abnormal growing conditions. Look for consistency in a hybrid's performance across a range of environmental conditions. Grain moisture percentage at harvest can provide a basis for comparing hybrid maturity, especially when grain moisture levels average above 20% at a test site. Since drydown was so rapid this year, using grain moisture as an indicator of relative maturity may be of somewhat limited value this year compared to past years (especially 2009). Similarly, the exceptionally low level of stalk lodging this year provides a limited basis for making comparisons of stalk quality among hybrids. Yield, standability, test weight, and other comparisons should be made between hybrids of similar maturity to determine those best adapted to your farm. Results of the crop performance trials for previous years are also available online at: http://www.ag.ohio-state.edu/~perf/archive.htm

 

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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.