Christy Sprague...Glyphosate-resistant weeds continue to be of growing concern for growers, particularly since several different glyphosate-resistant weeds have been identified in the states surrounding Michigan. Weeds that often escape control in Roundup Ready fields include horseweed (marestail), common ragweed, giant ragweed, and common lambsquarters. While not all weeds that escape control are resistant, it is important to identify the cause of the lack of control.

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Christy Sprague...Late-season rains and later than normal canopy closure have led to several weedy soybean fields. These weeds can lead to difficulties with harvest if stems or leaves are still green. Frost usually helps desiccate these weeds, however if soybeans are ready to be harvested before weeds have dried down, there are a few herbicide options that growers can use as harvest aids to help desiccate or dry down “green” stem and leaf tissue.

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By Wesley Everman...The development of stacked trait technology and the increased interest in herbicide tolerant corn has led to an increase in postemergence herbicide applications for weed control. Postemergence programs without a residual herbicide applied at planting have their place, and can provide excellent season long weed control. However, important considerations that should be made include timing, herbicide resistance, and management strategies.

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By Christy Sprague... Postemergence herbicide applications for weed control in Roundup Ready soybean are quickly approaching. There are several things that should be considered to maximize weed control with glyphosate from these applications in Roundup Ready soybean. Following these guidelines can help reduce the risk of glyphosate failures, as well as reduce the chances of lower soybean yields due to weed competition.

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By Christy Sprague... We are now coming into our second year of using Roundup Ready sugarbeets in Michigan. For most of us, the use of glyphosate (Roundup) in Roundup Ready sugarbeets has made weed control simpler and more consistent. However, as with any changes in production practices there is still a learning curve to using this technology.

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By Christy Sprague... Driving around the state, I have noticed several no-till fields that still have carpets of winter annual and some newly emerged early summer annual weeds, like common lambsquarters and giant ragweed. With the wet conditions keeping many growers out of the field, soybean planting is occurring at a slower pace and once conditions are favorable many growers may opt to plant first and apply a burndown later.

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By Christy Sprague... Flexstar GT is a new herbicide premixture recently registered by Syngenta. This premixture contains the active ingredients fomesafen (Flexstar) and glyphosate. Because of the unique modes of action of each of these active ingredients, Flexstar GT is being marketed to control weeds that are resistant to or may be harder to control with glyphosate alone.

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By Christy Sprague... Before you schedule your vacation this summer, make sure to get the 2008 MSU Weed Tour marked on your calendar. The 2008 MSU Weed Tour will be held on Wednesday, July 1 at the Michigan State University Crop and Soil Sciences Teaching and Research Field Lab.

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By Christy Sprague and Wesley Everman... The 2009 Weed Control Guide for Field Crops, MSU Extension Bulletin E-434 is now available online at http://www.msuweeds.com/publications/2009_weed_guide/.

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By Wesley Everman... There are two important corrections to the print version of the 2009 Weed Control Guide for Field Crops in the corn section. Please take a minute to turn to these pages and make the corrections listed below.

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By Wesley Everman and Christy Sprague... Over the last five seasons, we have conducted field trials that have examined the economics of commercial weed control programs in corn and soybeans currently marketed to Michigan growers.

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Diane Brown-Rytlewski...High market prices for both corn and soybeans this year are once again tempting growers to consider applying fungicides in the absence of disease. Whether or not a yield increase will result continues to be a topic of many lunch counter discussions, and among plant pathologists.

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Christy Sprague...Early season weed competition may be one of the biggest contributors to unseen yield losses in soybean. Appropriately timing postemergence herbicide applications is critical to preserving crop yields. Several studies have shown that delaying postemergence weed control strategies can substantially reduce crop yield. This has become more of a concern with the large number of glyphosate-resistant crop acres that rely on postemergence applications of glyphosate for weed control.

[Read the rest of this article...]

Christy Sprague...Postemergence herbicide applications for weed control in soybean are quickly approaching. There are several things that should be considered to maximize weed control with glyphosate from these applications in Roundup Ready soybean. Following these guidelines can help reduce the risk of glyphosate failures, as well as reduce the chances of lower soybean yields due to weed competition.

[Read the rest of this article...]

Christy Sprague...As we are on the front edge of the fungicide applications for Rhizoctonia management in sugar beets, many of these applications often coincide with herbicide applications for weed control. While tank-mixing these two pest management practices could save extra trips across the field, there are some risks associated with tank-mixing certain herbicide programs with fungicides.

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Wes Everman...Winter annual weeds can be problematic and reduce forage quality and yield in alfalfa during the spring of the year. The best method for weed management is good stand establishment and to control weeds in the fall or spring with herbicide applications to dormant alfalfa. Several herbicides are labeled for control of grass weeds, broadleaf weeds, or both when applied to dormant alfalfa.

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Wes Everman...As discussed in a previous Field CAT Alert article, preemergence herbicides should be applied as soon after planting as possible because delayed application increases the risk of poor herbicide performance, especially for grass control. Delayed preemergence applications were covered in detail, but what if you are able to make your preemergence application and the weather is cold, or extremely wet or dry after planting?

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Christy Sprague...Driving around the state, I have noticed several no-till fields that still have carpets of winter annual and some newly emerged early summer annual weeds, like common lambsquarters and giant ragweed. With soybean planting in full swing, it is extremely important that these weeds be controlled prior to soybean emergence. Ideally, these weeds should have been controlled prior to planting, but because many of these fields have already been planted it is important to control these weeds prior to soybean emergence.

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Christy Sprague...This year almost 50 percent of Michigan’s sugarbeet acres are planted to Roundup Ready sugarbeets. While the timing of glyphosate (Roundup, etc.) may not be as critical for weed control as some of the strategies that we currently use i.e., micro-rates and standard splits, there is still 50 percent of the acres that are planted with conventional sugarbeets. Timely herbicide applications over these acres are critical for adequate weed control.

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Wes Everman...Although many people have rotated corn to soybeans or other crops this year, if you are planting corn following corn there are several weed management issues to consider. Herbicide inputs are a greater concern in a continuous corn system when compared to growing corn in rotation with another crop. This is due primarily to increased crop residue levels as well as weed escapes from the previous year.

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Wes Everman...Preemergence herbicides should be applied as soon after planting as possible because delayed application increases the risk of poor herbicide performance, especially for grass control. However, there can be challenges for herbicide application following planting, such as high winds and rainfall. Therefore, it is likely there will be situations where corn has emerged before preemergence herbicides have been applied.

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Christy Sprague...The use of postemergence (POST) glyphosate in Roundup Ready soybeans has been the primary weed control program used by many Michigan soybean growers. While this system has seemed to simplify weed management, relying on total postemergence herbicide programs can be difficult to manage if not properly implemented. The flexibility in application timing that glyphosate offers may make it easier to control larger weeds, however the benefits of early-season weed control to protect crop yield can be lost if applications are not made in a timely manner.

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Christy Sprague...Of all the crops grown in Michigan, winter wheat has typically been the crop that has not been intensively managed. However with higher wheat prices, growers are looking at more intensive management to maximize yield. Where weeds are present, herbicide applications to control both winter and summer annuals is one management practice that may improve yield at the end of the season.

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Christy Sprague...After a long wait, Michigan sugar beet growers will be growing Roundup Ready sugar beets for the first time this year. For most of us, the use of glyphosate (Roundup) in Roundup Ready sugar beets should make weed control simpler and more consistent. However, as with any change in production practices there will be a learning curve to using this technology.

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Joe Armstrong and Christy Sprague...No-till soybean production in Michigan relies almost exclusively on glyphosate for preplant and postemergence weed control. While glyphosate continues to provide excellent control of most weeds, timely applications before planting and after soybean emergence are necessary to ensure the best growing conditions for your soybean crop. The following recommendations are based on MSU research funded by the Michigan Soybean Promotion Committee (MSPC).

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Christy Sprague and Wesley Everman...The 2008 Weed Control Guide for Field Crops, Extension Bulletin E-434 is now available online at http://www.msuweeds.com/publications/2008_weed_guide/. It is also available in print at the MSU Extension Bulletin office by calling (517)353-6740 or your county Extension office.

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David Hillger and Jim Kells...Typically, management of annual weeds in wheat stubble is not difficult, however timeliness is critical. These weeds must be managed soon in order to prevent seed production. Several effective options are available for management of annual weeds in wheat stubble. However, these practices must be implemented before seed production to avoid significant additions of seeds to the weed seed bank. After wheat harvest, weeds take advantage of available resources, especially newfound sunlight, and will grow rapidly with adequate soil moisture.

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Christy Sprague...Over the last week common pokeweed plants have become more apparent in several Michigan fields. While common pokeweed is generally not a problem that most Michigan farmers think about, this weed has become increasingly prevalent throughout most of the state. In fact, in some cases common pokeweed infestations have reached populations that could interfere with crop yields.

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Christy Sprague...Early season weed competition may be one of the biggest contributors to unseen yield losses in soybean. Appropriately timing postemergence herbicide applications is critical to preserving crop yields. Several studies have shown that delaying postemergence weed control strategies can substantially reduce crop yield. This has become more of a concern with the large number of glyphosate-resistant crop acres that rely on postemergence applications of glyphosate for weed control.

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David Hillger...For several years, MSU has demonstrated the importance of timely herbicide applications to prevent the loss of yield in corn. We have shown that it is necessary to control weeds before they reach 4 inches of growth to prevent measurable yield reduction. Two-pass herbicide applications (preemergence followed by postemergence or two postemergence) or timely single postemergence applications with residual control, are most effective at preserving yield and maximizing gross margin.

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Christy Sprague...Crop rotation and replant restrictions for herbicides are extremely important to follow prior to planting. One of the desired characteristics of an herbicide can often be residual activity for weed control. However, this characteristic can also cause some headaches if the rotation restrictions are not followed. Herbicides need sufficient time to dissipate or breakdown prior to planting crops that are more susceptible to that herbicide.

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David Hillger and Jim Kells...There can be many challenges for herbicide application following planting, such as high winds and rainfall. Therefore, it is likely there will be situations where corn has emerged before preemergence herbicides have been applied. In fields with emerged corn and no herbicide applied, growers have two primary options: to use an herbicide program typically applied before emergence; or switch to a total postemergence strategy. There are several possible herbicide programs with each strategy.

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Christy Sprague...Recent rains and warm temperatures have contributed to good sugar beet emergence in many areas of the state. However, along with the sugar beets has come excellent emergence of several weeds. Growers who are planning to use micro-rate herbicide applications for weed control, should have made their first micro-rate application for many of the beets planted on or before April 21 in most areas of the state. Rain and wet conditions have caused many of these applications to be delayed.

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Steven Gower...Glyphosate-resistant horseweed (Conyza canadensis) has been confirmed in a Christmas tree plantation in Mason County, Michigan. This detection represents the 16th state in the United States with glyphosate-resistant horseweed (Heap 2006). Also known as marestail, horseweed is a troublesome weed in no-till field crops, fruit crops, tree plantations and nurseries throughout Michigan.

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Christy Sprague...In the following article in this issue of the Field Crop CAT Alert, Steve Gower with MSU Diagnostic Services reports the first confirmation of glyphosate-resistant horseweed (or marestail) in Michigan. Steve has been actively screening weed samples for glyphosate-resistance over the last five years. We have been extremely lucky in Michigan, because of all of the samples that Steve had tested over the years none had been confirmed glyphosate-resistant until now.

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Christy Sprague...Giant ragweed is an early germinating, summer annual weed species that is commonly found throughout the southern two tiers of Michigan counties and throughout many areas of the Midwest.  Surveys conducted in several Michigan counties this year ranked giant ragweed one of the most problematic and common weed escapes in both corn and soybean fields.  Giant ragweed possesses several characteristics that contribute to its ranking.

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David Hillger and Jim Kells...Growers have the option of using tillage and/or herbicides to remove a forage stand. If they choose to use herbicides, the ideal time to kill an established legume stands is in the fall. When removing a clover cover crop or an old alfalfa sod, the most effective and consistent approach to killing these forages is similar. The field should be mowed in late August or very early September in central and Lower Michigan or mid-August in northern Michigan.

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Steven Gower and Wendy Osman...Earlier this season in St. Joseph County, a farmer found out the hard way that yews (Taxus spp.) are extremely toxic to cattle. A few overgrown bushes were removed from a landscape one afternoon and pulled into a pasture area. The intention was to burn them once all were removed and dried. The next morning, all 10 cattle in the pasture were dead. Plant material submitted to the lab was identified as Japanese yew (Taxus cuspidata).

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Jim Kells and Kathrin Schirmacher...Annual weed densities are very high in wheat stubble this year. These weeds must be managed soon in order to prevent seed production. Several effective options are available for management of annual weeds in wheat stubble. However, these practices must be implemented before seed production to avoid significant additions of seeds to the weed seed bank.

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Christy Sprague...Later planted and replanted crops have put us in the situation where postemergence herbicide applications will be made to several different crops during the same time period. Because of the vast number of acres that need to be sprayed with different types of products, caution needs to be taken to avoid spray tank contamination.

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Christy Sprague and Jim Kells...Early season weed competition may be one of the biggest contributors to unseen yield losses in corn and soybean. Appropriately timing postemergence herbicide applications is critical to preserving crop yields. Several studies have shown that delaying postemergence weed control strategies can substantially reduce crop yield.

[Read the rest of this article...]

Jim Kells, Kathrin Schirmacher and David Hillger...There are several herbicide options for postemergence weed control in corn. The best choice for any given field depends on the specific situation. Three of the critical factors to consider when selecting a postemergence herbicide in corn are:

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Kathrin Schirmacher, Dave Hillger and Jim Kells...There have been several questions about the possibility of failed preemergence herbicide applications and the likelihood of annual grass weed escapes, particularly more difficult to control weeds such as large crabgrass. Emerged large crabgrass is difficult to control in conventional systems with smooth crabgrass being even harder to control.

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Christy Sprague...Soil-applied herbicides remain an important part of weed control programs in corn and to a much lesser extent in soybeans. Because of the dry soil conditions that we experienced in April and the first couple of weeks of May, soil-applied herbicides were applied under conditions where there was little or no rainfall for incorporation leaving many of these herbicides on the soil surface.

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Christy Sprague...As the end of May quickly approaches dry beans will soon be planted throughout most of the state. One pest that can lead to major yield reductions, quality problems and issues with harvest are weeds. To help stay ahead of these pests, below is a summary of what weed control options are available in dry edible beans with approximate herbicide costs.

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David Hillger, Kathrin Schirmacher and Jim Kells...There are over 280 products (commercial and ready-to-use) with glyphosate currently registered for use in Michigan. One of the main differences among the many available products is the surfactant component of the formulated products; some may need additional surfactant while others do not (See Table 10, p. 132 in the 2006 Weed Control Guide for Field Crops, E-434 for a listing of the commercial products used in agriculture).

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Christy Sprague...There are over 30 different glyphosate products that growers in Michigan can choose from for weed control in glyphosate-tolerant (Roundup Ready) crops. With all of these choices, it is important to keep in mind that not all glyphosate formulations are created equal. Knowing your glyphosate product is essential to achieving optimum weed control.

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Steve Gower...Horseweed (Conyza canadensis), also known as marestail, is an annual weed that has developed resistance to a number of popular herbicides over the past few years. Currently, glyphosate-resistant horseweed has been confirmed in at least thirteen states in the Eastern U.S. with ALS resistance reported in Ohio, Indiana, and Michigan. (See Photo)

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Christy Sprague...Timely burndown herbicide applications in no-till fields are extremely important in protecting soybean yield. Within the next two weeks soybean planting will be in full-force. As several no-till drills start planting fields, remember the importance of a timely burndown application. The tendency for a number of growers, particularly those planting Roundup Ready soybean, will be to plant into a weedy mess and not worry about applying their burndown herbicide until later or to wait until most of the summer annual weeds have emerged before making their first postemergence glyphosate application.

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Jim Kells, Kathrin Schirmacher and David Hillger...There can be many challenges for herbicide application following planting such as high winds and rainfall. Therefore, it is likely there will be situations where corn has emerged before preemergence herbicides have been applied.

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Jim Kells, David Hillger and Christy Sprague...Dandelion continues to be a serious problem in Michigan, mainly in no-tillage fields. Regular soil disturbance is effective at preventing the establishment of dandelion plants; however herbicide options are available to suppress dandelion in corn, soybean and alfalfa.

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Christina DiFonzo...There is a tremendous amount of low-growing weeds this spring. These weeds may be attractive to certain insects, especially cutworm, that lay eggs in weedy corn. Thus, timely weed control is critical to reduce infestation.

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Christy Sprague...The use of postemergence (POST) glyphosate in Roundup Ready soybeans has been the primary weed control program used by many Michigan soybean growers. While this system has seemed to simplify weed management, relying on total postemergence herbicide programs can be difficult to manage if not properly implemented. The flexibility in application timing that glyphosate offers may make it easier to control larger weeds, however the benefits of early-season weed control to protect crop yield can be lost if applications are not made in a timely manner.

[Read the rest of this article...]

Jim Kells, David Hillger and Kathrin Schirmacher...Once wheat has passed Feeke’s Stage 6, the risk of herbicide injury from 2,4-D, MCPA, Banvel/Clarity, or Curtail increases and application of these herbicides is not recommended. In this situation, the remaining herbicide options for broadleaf weed control are Harmony Extra, Harmony GT, Express, Buctril, Stinger and Starane. Harmony Extra, Harmony GT, Affinity BroadSpec and Express can be applied to wheat until the flag leaf is visible (before Feeke's Stage 8).

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Jim Kells and Kathrin Schirmacher...There are currently a large number of winter annual and perennial weeds present in no-till corn and soybean fields. It is important to control these weeds prior to crop emergence. These weeds may become very competitive if not controlled.

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Christy Sprague...Recent rains and warm weather coupled with some of the earliest planted sugar beets in Michigan history has started the clock for postemergence weed control. Along with sugar beet emergence, weeds like common lambsquarters and velvetleaf have started to emerge in sugar beet fields. Starting now, timely postemergence herbicide applications will be critical for effective weed control programs, particularly for growers who will be using micro-rates.

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Christy Sprague, James Kells and Kathrin Schirmacher...Over the last two seasons we have conducted field trials that have examined the economics of commercial weed control programs in corn and soybeans that are currently being marketed to Michigan growers.

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