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June 2009 Archives

Losses in Wheat due to Flooding and Waterlogging

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Northwest Minnesota continues to be plagued by excess precipitation. Consequently many field or lower lying portions of fields are repeatedly flooding or are - at a minimum - completely waterlogged. Flooding and water logging causes a rapid depletion of oxygen in the root zone. In turn, this oxygen deficiency affects several physiological processes such as the uptake of water, the uptake and transport of nutrients, and the root/shoot hormone relations.

Wheat can probably handle 3 to 4 days of flooding and/or water logged soils before grain yield is impacted negatively as long as some of the leaves are above water. Higher temperatures will hasten the depletion of oxygen and increase the risk of damage to the crop. Acute nitrogen deficiencies are most commonly observed with the crop yellowing quickly. The waterlogged soils not only impair nitrogen uptake, denitrification and leaching further exuberate the problem. Extended periods of water logging reduce leaf elongation, kernel number, and ultimately grain yield.

Yield losses than have been reported in the literature range between 20 to 50% when soils were water logged in excess of 10 days. One study in winter wheat reported a yield loss of about 2% for each day soils were waterlogged. Several study, however, have also noted differences in water-logging tolerance among wheat varieties.

One of the characteristics that were observed of varieties that handled water logging better than other varieties was the ability of varieties to initiate adventitious roots of the first node (Photo 1). I have observed this trait in some of our spring wheat varieties but neither I nor any of the breeding program in the region have dedicated screening or evaluation nursery for this trait.

09 Adventitious wheat roots.JPG
Photo 1. Adventitious roots on the first node of a wheat stem visible after three days of flooding near Crookston in 2002.

Soybean Rust: What will this year bring?

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by Phillip Glogoza, Extension Educator - Crops

Soybean rust was found in 392 counties in the United States in 2008. This is the highest number of counties reporting the disease since it was first discovered in the continental U.S. in 2004. Soybean growers in Alabama were encouraged to use fungicides on at risk beans in late August, many neighboring states reported mostly low infection levels throughout the month of September as the crop matured.

Alfalfa Weevil: Coming on Strong in West Central MN

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by Doug Holen, Extension Educator - Crops, Fergus Falls
and Phillip Glogoza, Extension Educator - Crops, Moorhead

Just a quick note to report a significant outbreak of alfalfa weevil in WC MN. It escalated over the weekend with a lot of spraying starting on Monday. We have fields in all stages with 1st crop still standing, cut alfalfa in windrow for some time, and 16" of 2nd crop regrowth. All fields have been hit hard. All alfalfa growers in west central MN should be checking for possible infestations.


By Dr. Charla Hollingsworth, Plant Pathologist, U of Minnesota Extension
and Dr. Sam Markell, Plant Pathologist, NDSU Extension Service

This past week, the fungus that causes rust on sunflower, Puccinia helianthi, was identified on wild and volunteer sunflowers in Minnesota and North Dakota. The rust fungus is known as a "macrocyclic" pathogen because it produces five successive types of spores during its lifecycle. While all five types of spores are produced on sunflower, only one type is responsible for causing rust epidemics.

Wireworms in Small Grains

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by Dr. Ian MacRae, Extension Entomologist

I've received reports of wireworms in small grains this season - not surprising this year given that wireworm tend to be more active in cooler conditions. There are several species of wireworms in the Red River Valley and although they're usually neither a frequent nor wide-spread problem in the RRV, when they do occur, damage can be quite significant even leading to a total field loss.

Controlling Canada thistle with Milestone

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By Carlyle Holen, IPM Specialist, U of Minnesota Extension

What is the optimum time to treat Canada thistle (Figure 1) in non-cropland with Milestone? Based on field trials at Ada in 2007 the window for application is pretty wide and perhaps a better way to frame the question might be: What is the least effective time to treat Canada thistle? In the Ada trials, applications were made at two week intervals from June 1 to August 23 (Table 1). We found new shoots are initiated on a nearly continuous basis during the growing season with a large 'flush' of new rosettes in the spring and in late summer /early fall after older plants have finished dispersing seed. During the spring 'flush' new stems are rapidly added by the extensive root system and a single plant may have dozens of individual, interconnected stems. Figure 2 shows the increase in Canada thistle stem number, from June 1 to August 23 from untreated plots. In the two week period from June 1 to June 15 there was a 44% increase in stem number and from June 15 to June 29 the increase was 18%. The speed of shoot emergence is driven initially by soil temperature and continues at a fairly rapid pace until plants begin to flower. With a continuous emergence of new Canada thistle shoots you will find stems that are blooming next to ones that are just emerging. When staging plants make your assessment on the most advanced plants in the patches.

By Phillip Glogoza, Extension Educator - Crops

The cool temperatures have delayed alfalfa weevil population development in the region. In west central MN, first cut got underway two weeks ago. As we move northwest, first cut may just be beginning for some. In some cases, cutting alfalfa may have removed significant eggs laid in stems, while in other sites young larvae are feeding in the growing terminals, whether it is regrowth or uncut alfalfa.

Causes of Seedling Stand Losses in Spring Wheat


Seedling stand loss is defined as the percentage of viable seed that fails to become a healthy plant. In order to understand the causes of stand loss we need to also define seedling vigor. Seedling vigor is defined as those seed properties that determine the potential for rapid, uniform emergence and development of normal seedlings under a wide range of conditions. Causes of seedling stand losses can be categorized in three broad categories - intrinsic attributes, biotic stresses, and abiotic stresses.

Both seed size and grain protein content have been shown to improve seedling vigor in spring and winter wheat seed lots of the same cultivars that have higher seed weight and/or grain protein content will have more seedling vigor. Some of the research, however, suggested that there was no need to remove the smaller seed fraction from a seedlot as long as the seedlot had commercially cleaned as there often wasn't a yield difference at the end of the season despite differences in seedling vigor. Some of the same research, however, did shown that were significant differences in seedling vigor among spring wheat cultivars and the authors of the studies suggested that breeders use it as a selection criterion in their breeding programs.

A cold stress test in addition to the standard germination test is a method to test seedling vigor of a breeding line, variety or seedlot. Corn breeders routinely use this test as a selection criterion in their breeding programs. I am not aware of any spring wheat breeding programs that use the cold stress tests in their breeding program. This can probably be explained by the fact that corn is more often seeded in - for corn - cold soils resulting in protracted germination and seedling emergence.

The physiological age of the seed is also an important parameter that influences seedling vigor. A standard germination test is used to determine the percentage viable seed under ideal conditions. There is also the 'accelerated aging test' to discern seedlots with poor seed vigor and excellent seed vigor. This test is routinely conducted in soybeans and corn but again seldom used in wheat. This too can probably be explained by the fact that corn and soybeans are more often seeded for their species in cool soils, resulting in protracted germination and seeding emergence.

Biotic stresses that cause stand losses include whole host of fugal diseases. Saturated and/or cold soils can aggravate the incidence and severity of a number of fungal seeding diseases including Pythium damping off.

Abiotic stresses that cause stand losses are water, temperature, and/or distance to the soil surface. Excess moisture (anytime the soil water content is above field capacity) depletes the soil of oxygen and germinating seed will quickly die in these anaerobic conditions. High temperatures in excess of 90F can induce a dormancy that will prevent germination. This dormancy is not broken until temperatures drop below 50F. Seeding too deep will prevent to coleoptile to reach the surface, and consequently, the first leaf will not get above ground. The seedling will ultimately die although an etiolated and crinkled up first leaf can often be found just below the soil surface. Crusting of the soil can give a similar result. Seeding too shallow or in a seedbed that is very cloddy poses the risk of poor seed to soil contact. In either case, the seed can not in imbibe enough water for germination to start. This seed will stay viable until a rain improves seed to soil contact and adds water into the upper soil layer. A big risk, however, is that the seed will start to imbibe water but that wind and/or warmth desiccate the seed again. This almost always means the death of the germ.

Judging from some of the fields I have surveyed, the shallow seeding and the anaerobic conditions have contributed equally to the uneven emergence we see in many fields. A clue whether shallow seeding contributed to a delay in emergence is to dig up the seedling and measure the distance from the crown to the tip of the coleoptile. You also count the number of leaves of these seedlings and compare this to the better parts of the field. Given the fact that it takes about 180 GDD for each leaf to appear, you can use the difference in development to reconstruct whether the seed lay in dry dirt; the number of days needed to accumulate difference in GDD should be equal to the number of days between seeding and the first rain received after seeding.

Continuous Corn in Minnesota: How do we do it?


In 2008 University of Minnesota Extension launched an on farm research project evaluating continuous corn production under a series of different tillage systems on six farms across Minnesota. For the sake of brevity this article will only address one site in Southeastern Minnesota that is located near Faribault.

The tillage systems studied include a conventional moldboard plow system, a chisel plow system representing a traditional conservation tillage, and strip till as a higher residue conservation tillage system.

Now is The Time to Evaluate Stands


The challenging spring in Northwest Minnesota has forced many to seed their wheat and barley under less than ideal conditions and into poor seedbeds. Now is the time to evaluate how well your seeding operation went and what the attained stands are. This is important as the decision about inputs further into the season will depend on the yield potential that is left.

Glyphosate-resistant biotypes of giant and common ragweed and common waterhemp have been confirmed in Minnesota and are listed on the International Survey of Resistant Weeds web site at: Both species appear to be resistant to approximately four-times the labeled use rate of glyphosate (4X).

In the short time frame presented to us during the growing season, separating glyphosate nonperformance due to resistant weed biotypes from other factors is an inexact and qualitative process but a quick response could help reduce the spread of glyphosate resistant weeds and set-up long-term management plans.

Temperatures Affect Glyphosate Activity

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Temperatures over the last month have fluctuated greatly. Cold temperatures two weeks ago caused a reduction in glyphosate activity. Individual plants of lambsquarters and annual smartweed species where not completely controlled at a research location while other plants and other species were completely controlled. Cold weather in early June of 2008 also caused a reduction in glyphosate activity. The cold weather last week and early this week will likely cause glyphosate applications to be less effective until warmer temperatures persist.

Soybean Planting Date and Delayed Planting

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We are into the fourth year of a soybean date planting trial at Crookston investigating how two different relative maturity soybean varieties respond to planting date. Results for 2006 - 2008 show maximum soybean yield when planting in the May 1 - 15th window of opportunity. Previous planting date trials from the University of Minnesota also show an optimum planting window of May 10 - 20 to achieve maximum yield (Table 1).

The control of perennial noxious weeds can often be troublesome for farmers, CRP landowners, county and township road/weed department officials, and other land managers. Thanks to modern technology and a better understanding of biological control methods, land and roadside managers have new and effective tools to control such problem weeds. This plot tour and educational programplans to address these topics.

Orange Wheat Blossom Midge: Vigilance is in order

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Orange wheat blossom midge (Figure 1) as a wheat pest has been off the front page as a major production problem in NW MN for many years. Populations in the region have been small enough that significant outbreaks and associated yield losses have been of small concern. However, we learned in the mid-90’s that given the right circumstances, this insect can increase its population rapidly and cause major yield losses in a very short time frame.

Volunteer Corn Management in Corn and Soybean

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Large populations of volunteer corn are being reported in some fields in Minnesota this year. What impact the volunteer corn will have on this year’s crop yield and the viable management options available will depend upon in which crop the volunteer corn is present. Making the assumptions that the majority of the volunteer corn present is glyphosate resistant and that glyphosate resistant crops were planted in the field this year, your only management option in corn at this time is cultivation. In soybean you have the herbicide options of the ACCase inhibiting herbicides such as: Select Max (clethodim), Fusilade DX (fluazifop-P), Fusion (fluazifop-P & fenoxaprop) and Assure II (quizalofop); note Poast Plus (sethoxydim) is not as active as the other herbicides on volunteer corn. The ACCase inhibiting herbicides are generally targeted on 12- to 24-inch tall volunteer corn. The ALS herbicide, Raptor can also effectively control smaller (2 to 8 inch) volunteer corn.

Blending of Wheat Varieties - II

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In a previous article that appeared in Prairie Grains Magazine and the Farm & Ranch Guide blog, I discussed the merits of blending different varieties of spring wheat. The harsh winter and spring have added another dimension to this discussion that demands some attention.

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