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Extension > Minnesota Crop News > July 2017

Monday, July 31, 2017

Pyrethroid resistant soybean aphids: What are your control options?


Bruce Potter (Extension IPM Specialist, U of MN), Robert Koch (Extension Entomologist, U of MN), Phil Glogoza (Extension Educator – Crops, U of MN), Ian MacRae (Extension Entomologist, U of MN), and Janet Knodel (Extension Entomologist, NDSU)

We are receiving an increasing number of reports of pyrethroid insecticide failures for soybean aphid management from northwest and central Minnesota, and northeastern North Dakota this year. However, many areas of Minnesota and North Dakota still have low, non-yield threatening aphid numbers and scouting should continue to determine when to apply insecticides.

In this article, we review the insecticide groups used for soybean aphid control (Table 1) and discuss the potential role of and challenges associated with insecticide mixtures.

Wednesday, July 26, 2017

Uncovering dicamba herbicide's wayward ways

by Jeff Gunsolus, Extension weed scientist


Leaf cupping symptoms of dicamba injury in soybean. Photo: Fritz Breitenbach
Dicamba injury to non-target soybeans has been widely reported in south central and southwest Minnesota. Symptoms range from cupping and strapping of newly emerged leaves to height reduction and injury to growing points. At low dicamba concentrations, symptoms were slow to emerge, showing up 14 to 21 days after exposure. The big unknown, of course, will be impact on soybean yield, which will require negotiations now to determine the most accurate in-field yield comparisons later.

Monday, July 24, 2017

Estimating Grain Small Grains Grain Yields

The USDA-NASS' July 1 yield forecasts for barley, oat, and spring wheat were 67, 71, and 61 bushels per acre, respectively.  This would mean a new state record for spring wheat, while the forecast for barley and oats are 10 and 7 bushels off the records set in 2015.

To estimate yield the USDA-NASS collects farmer's assessment of yield prospects throughout the growing season, i.e. the USDA-NASS asks producers to predict their final yield. At first glance, this may seem a bit unscientific and not very accurate. The statistical methods that are used to crunch the collected data and have it confess a forecast, however, are robust and because enough producers are surveyed, the forecasts have been proven predictive at the aggregate level.  This is, in a way, a testament that you each know you crop and operation pretty well. The completely methodology can be found here.

Luxury Uptake of Boron: How Much is Too Much?


By Dan Kaiser, Extension Soil Fertility Specialist

The ultimate goal of nutrient management is to ensure that the plant has enough nutrients to produce maximum potential yield. This involves monitoring soil nutrients and crop uptake, and often supplementing nutrients that the crop is lacking. But what happens when the plant takes up more than enough of a certain nutrient? That’s called luxury uptake. Though it isn’t usually a problem for crops, it can become an issue if a nutrient reaches toxic levels in a plant. In Minnesota, the main concern is with Boron in soybeans and other broadleaf plants.

Friday, July 21, 2017

Soybean aphid infestations and reports of failures of pyrethroid insecticides to control soybean aphid



Robert Koch (Extension Entomologist), Ian MacRae (Extension Entomologist), Bruce Potter (Extension IPM Specialist), and Phil Glogoza (Extension Educator – Crops)

By now you should be scouting your soybean fields for soybean aphid on a regular basis.  Soybean aphid can be found in most fields throughout the state and populations have reached economic threshold (250 aphids per plant) in some fields in northwest Minnesota and have require insecticide application to protect soybean yield.  In northwest Minnesota (especially around Norman County), applications of pyrethroid insecticides are failing to adequately control aphid populations in some, but not all, fields.  

Thursday, July 20, 2017

The Dicamba Dilemma: Facts and speculations

Used with permission by Aaron Hager, University of Illinois

dicamba-injury-soybean
Dicamba injury to soybeans in a southwestern Minnesota field. Photo: Stephan Melson
Dicamba injury to non-target crops has dominated Extension discussions this week. Non-tolerant soybeans are extremely sensitive to this chemical and damage has been reported in a number of fields throughout the state. The following article by Dr. Aaron Hager at the University of Illinois echoes observations we have been making in Minnesota and summarizes injury symptoms on soybean, possible routes of exposure, and potential yield effects. His article is reprinted in its entirety:

Wednesday, July 19, 2017

Herbicide Mode of Action and Crop Injury Symptoms at the University of Minnesota Field School for Ag Professionals

by Dave Nicolai, IAP Program Coordinator

This year at the Field School, participants will have two opportunities to learn, re-learn or fine-tune their skills in linking visual symptomology to the common herbicide modes of action commonly used in corn and soybean and gain in-depth knowledge of growth regulator herbicide movement and symptomology in soybean.

Weed management has changed dramatically in recent years. The large number of herbicide options—new products, old products with new names, new formulations of old products, premixes, and generics—can make weed control appear to be a difficult and confusing task. Knowing and understanding each herbicide’s mode of action is an important step in simplifying and selecting the proper herbicide for each crop, diagnosing herbicide injury, and designing a successful and durable weed management program for a farmer’s production system.

Tuesday, July 18, 2017

Lunch and Learn Webinar: Managing Ash Content in Hay

Krishona Martinson - University of Minnesota

On Wednesday, August 23, 2017 from 12:00 to 1:00 pm (central time), the University of Minnesota will host a free webinar titled “Managing Ash Content in Hay”. Dr. Marvin Hall, Professor of Forage Management from Penn State University, and Abby Neu, Extension Educator from the University of Minnesota Extension, will present the webinar.

Hay Rake Impacts Ash Content in Alfalfa Hay

Abby Neu, Craig Sheaffer, Scotty Wells and Krishona Martinson, University of Minnesota; Marvin Hall and Dan Kniffen, Pennsylvania State University; and Dan Undersander, University of Wisconsin.

Summary: Using a hay merger or sidebar rake to combine swaths resulted in less ash content compared to a wheel rake; however, rake-type rarely resulted in differences in forage nutritive value. In addition to wide swaths, cutting heights ≥2 inches, and flat mower knives, the use of a hay merger or sidebar rake can be added to the list of best management practices to reduce ash content in alfalfa hay.

Pre-harvest Management of Small Grains

To save time and money most of you prefer to straight cut your wheat, barley, rye or oats.  The allow for straight cutting the crop has be evenly ripe across the field and the straw and grain has to be dry enough that it will feed through the combine.

Waiting for a whole field to dry down poses a risk for the portion of the field that is already harvest ripe, including sprout damage, straw breakage and lodging. To even out dry-down and/or speed up dry-down you have two basic options. Swathing or windrowing, at one time, was the default operation that signaled the beginning of harvest.  A second preharvest option is an application of glyphosate at the hard dough stage.

Glyphosate is labeled as a harvest aid to control late emerged weeds that may interfere with harvest. The RoundUp PowerMax II  label doesn't define it as a desiccant. Research has shown that glyphosate applied with or without ammonium sulfate may hasten drydown of the wheat crop if conditions for drydown are adverse. With a preharvest interval of 7 days, a couple of days, at the most, may be gained. Previous Minnesota Crop News post provide details about swathing and preharvest glyphosate.





White Heads

Jochum Wiersma, Ian MacRae, and Madeleine Smith

Is not the reincarnation of the Detroit rock due the White Stripes but a phenomenon that often can be seen this time of year in wheat fields are they are starting to ripen.  The causes of these premature ripened heads are varied and a diagnostic key can be found here.

People of commented that especially the wheat stem maggot is more prevalent this year and my travels to the different field trials across the state confirm this. The seemingly high numbers of wheat stem maggot may be related to the mild winter conditions.  Several insect pests that overwinter in Minnesota have had comparatively high and early populations this year.

Incidence will generally be worse along field edges and taper off as you walk further into the field.

Friday, July 14, 2017

4 Steps to More Effective Tissue Sampling


Daniel Kaiser, Extension Soil Fertility Specialist

For over 50 years, the practice of plant tissue sampling has been used to determine the status of nutrients in crops. More recently, there has been a movement to use tissue sampling to determine “hidden deficiencies” in the crop. While tissue analysis represents just one tool in the toolbox for managing nutrients and should be viewed like a report card, it can provide useful information in diagnosing problems when done properly. Here are the 4 things you need to make the most out of tissue analysis.

Monday, July 10, 2017

Register now for 2017 Field School for Ag Professionals

By Dave Nicolai, IAP Program Coordinator

2017-field-school
View video to learn more about Field School.
Agronomy training available this summer at the University of Minnesota Extension's 2017 Field School for Ag Professionals

The 2017 Field School for Ag Professionals will be held on July 27 - 28 at the University of Minnesota Agriculture Experiment Station in St. Paul. Field School for Ag Professional which is the summer training opportunity that combines hand-on training and real-world field scenarios. The two-day program focuses on core principles in agronomy, entomology, weed and soil sciences on the first day to build a foundation for participants and builds on this foundation with timely, cutting-edge topics on the second day.

Field Studies: Setting up a Trial

Josh Coltrain, Kansas State University; Sara Berg, South Dakota State University; Lizabeth Stahl, University of Minnesota; John Thomas, University of Nebraska Lincoln

plot-comparison
Photo 1. Example of an on-farm trial.
Higher yields, greater efficiency, reduced environmental impact!  This may sound like a used-car dealership sales pitch, but it could represent the objectives that make an operation sustainable. Increasingly, farmers are generating on-farm research data that encompass a wide-range of practical topics.  However, setting up those experiments so that the data is statistically valid is not necessarily common knowledge.

Thursday, July 6, 2017

Short(er) Spring Wheat Crop = Lower Grain Yield?

Some of you have noticed and commented that the spring wheat crop is shorter when compared to the last few years and subsequently questioned its yield potential. A few weeks ago, Dr. Joel Ransom wrote a nice article in the Crop & Pest Report explaining why the spring wheat crop was shorter and whether its yield potential had already been reduced.  

The physiology of grain fill has been well researched and we have a good understanding how temperature and droughts tress affect grain fill and grain quality. Table 1 summarizes the results of one of the published studies that illustrates how daytime and nighttime temperatures affect the length of the grain fill period and ultimately yield. The bottom-line is that higher nighttime temperatures are more detrimental than the maximum daytime temperatures.

Just in the last two days has the grain fill suffered some heat-stress, as maximum temperatures had not yet reached above 85F in the two weeks prior while minimum temperatures were mostly in the fifties in the same period (Table 2). 

Therefore, I am optimistic about this year’s yield potential, despite the shorter than normal crop as the first weeks of grain fill have been favorable, allowing for a larger proportion of the grain being produced de novo rather than being recycled from the shorter canopy.

The only caveat in this optimism is that the crop didn't suffer any other stresses these past two weeks. Drought stress poses the greatest threat but the cooler temperatures also reduced the crop's daily water consumption considerably.


Table 1 - Effect of daytime and nighttime temperatures on the length of the grain fill period and the average kernel weight (after Altenbach et al, 2003)

Tday
(oF)
Tnight
(oF)
Length Grain Fill
(days)
Thousand Kernel Weight (grams)
75
63
40
50
99
63
30
40
99
82
18
20


Table 2 – The daily maximum and minimum temperatures at 3 NDAWN locations in NW Minnesota and the number of days the temperatures were outside the optimum range for grain fill for spring wheat.
Date
Humboldt
Ada
Campbell
Tmax
Tmin
Tmax
Tmin
Tmax
Tmin







6/22
75
51
80
51
80
55
6/23
63
53
68
49
67
50
6/24
55
43
60
44
65
43
6/25
65
39
68
42
70
44
6/26
74
40
76
39
73
40
6/27
79
43
79
49
73
47
6/28
67
57
67
59
76
58
6/29
77
48
76
57
72
57
6/30
70
51
71
54
74
53
7/1
71
48
75
50
79
49
7/2
74
44
74
44
77
52
7/3
79
51
82
51
82
52
7/4
91
62
93
60
93
61
7/5
86
53
89
62
95
67







# Days Tmax>85
2
-
2
-
2
-
# Days Tmin>60
-
1
-
2
-
2


Wednesday, July 5, 2017

Do's and Don'ts of Late Season N in Wheat

Daniel Kaiser and Jochum Wiersma




Looking to improve grain protein in spring and winter wheat? Foliar applications of N during the onset of kernel fill have shown to effectively increase grain protein, but there are a few do’s and don’ts to keep in mind when it’s time to apply.

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