Vol. 20, No. 3, April 21, 2005

In this Issue
Recently planted fields at risk for insect damage later
Soybean aphid eggs hatch in central Michigan
Soybean aphids and virus transmission
General information on soybean rust
Cool weather and corn emergence
Loss of N from Urea
Weed management in wheat
Effectiveness of burndown herbicides for winter annual and perennial weed control in corn and soybeans
Weed control in non-GMO soybean
Spring has sprung and weeds are emerging in sugar beet fields: Start scouting!
New options for weed control in soybean
2005 Review of weed management options for dry edible beans
Regional reports
Major weather changes in progress

Next issue: May 5

Christina DiFonzo, Entomology

Congratulations to those of you who are done planting! But don’t let all that hard work go to waste – remember that certain insect problems are more common in early-planted, first emerging fields. Since many of these insects overwinter in Michigan, we could see some atypical cases of damage. Remember, the longer seed sits in the ground, the greater the period for insect feeding.

European corn borer: Larvae overwinter in crop residue. Adults start to emerge in May. Females are attracted to the earliest emerging (tallest) corn for egg laying. Scout early-planted fields for ECB first.

Flea hopper: Overwinter as adults. May carry and transmit the Stewarts wilt pathogen important in seed and sweet corn production.

Grubs: Grubs continue to be a problem across Michigan. Fields may have one or more species, most commonly Japanese beetle, European chafer and Phyllophaga (May/June beetle larvae). Chafer and Japanese beetle grubs generally stop feeding in mid- to late May, pupate and emerge as adult beetles. But fields planted in April are still at risk for root feeding.

Slugs: Slugs can be a greater problem in early-planted fields with heavy residue, especially fields that emerge slowly under cool, wet conditions (providing a greater time for slug damage). Ron Hammond at Ohio State (Dr. Slug) recently warned about slug problems this spring in the April 19 edition of the C.O.R.N newsletter at: http://corn.osu.edu/index.php?setissueID=79. The article also has a picture of slug eggs.

Grubs: Ditto my comments from the corn section. There are few options to protect soybeans planted into a grubby field. Cruiser seed treatment may be effective, but Syngenta lacks good research data at this point, so grubs are currently not on the label under beans.

Slugs: Can be a greater problem in early-planted fields with heavy residue that emerge slowly under cool, wet conditions (providing a greater time for slug damage). However, dry conditions do not favor slugs.

Christina DiFonzo, Entomology

Soybean aphid eggs hatched in my backyard buckthorn nursery on April 12. As a reminder, for the last few years in the fall, I placed potted buckthorn shrubs into a large aphid-infested cage used by Dr. Wang, the MSU soybean breeder. Aphids mated and laid eggs on the shrubs. In November, I moved the pots to my backyard for the winter. Hatch seems to coincide nicely with bud break. And because the infestation is generated in a cage, I know that the critters are really soybean aphids.

For comparison, here are the hatching dates from previous years on the same shrubs, at the same location: 2003, April 21. 2004, April 17.

Aphid hatch was also reported within the last few weeks in Illinois, Indiana, Ohio and Ontario.

Christina DiFonzo, Entomology

Below is an excerpt from a recent Vegetable CAT Alert article Viruses on vegetables likely to be a problem this year by Mary Hausbeck in the Plant Pathology Department.

“Whenever the numbers of soybean aphids have been high, viruses on vegetables have been a problem. If the numbers of soybean aphids increase this season, I am concerned that viruses, including cucumber mosaic virus, watermelon mosaic virus 2, zucchini yellows virus and others, may infect cucumbers, melons, pumpkins, zucchini, squash, peppers, tomatoes and even other vegetables. If resistant varieties are available, they could provide a measure of protection that would be important if soybean aphid numbers are high this year.”

Some additional comments from Chris: In the laboratory, soybean aphid transmits cucumber mosaic to zucchini with high efficiency. I have also had SBA transmit zucchini yellows. As far as field crops, SBA transmitted bean common mosaics in my laboratory; this virus can infect dry edible beans. In the literature, and in research labs, SBA has transmitted many other viruses, including soybean mosaic, alfalfa mosaic and potato virus Y.

Many common plant viruses in Michigan crops are in the potyvirus group. Viruses in this group are spread by aphids. Aphids must taste a plant (probe it) to determine if it is a host. In the process of tasting plants in the landscape, aphids accidentally pick up, move and transmit plant viruses. Potyviruses are transmitted in what is called a “non-persistent” manner. Virus particles contaminate the aphid’s mouthpart as it probes, then the particles are introduced into the next plant that it tastes. This form of transmission is essentially like that of human blood borne diseases spread by dirty hypodermic needles – except the aphid mouthpart replaces the syringe.

Nonpersistent viruses are picked up by aphids in a matter of seconds or minutes, and transmitted to a new plant in the same short time period. Because the transmission depends on short feeding probes, potyviruses infecting a given crop are transmitted primarily by aphids, which do not colonize that crop, and are simply visiting, tasting and rejecting that plant.

For example, in the early 1990s, small grain aphids from wheat fields were implicated in much of the potato virus Y spread in the Minnesota potato crop. Grain aphids didn’t like potato, so they kept probing in the landscape until they found an acceptable host, transmitting PVY in the process. Similarly, the increase in virus infection in Michigan vine crops in 2001 and 2003 tracked nicely with flights of soybean aphid. Soybean aphid does not like or live on zucchini or cucumbers, but we know from trapping data that millions of soybean aphids were landing in vine crop fields.

Because transmission is fast, and the vectors are often visitors, insecticides (foliar sprays and seed treatments) are usually not effective in preventing or reducing potyvirus transmission. The aphid is simply not exposed to the insecticide for a long enough period to kill it, or to disrupt transmission that occurs in a matter of minutes. Instead, the keys to reducing potyvirus infection are to:

§      Reduce virus source by planting clean seed or transplants;
§      Plant resistant hybrids if available;
§      Reduce aphid landing rate using reflective mulches, cover and border crops, etc.

Pat Hart
Plant Pathology

Ohio State University has a web site with links to just about every site anyone would need to keep them informed about the movement of soybean rust in the United States, predictions for movements, and a current list of available fungicides (http://www.oardc.ohio-state.edu/ohiofieldcropdisease).

The web site along with the following list for general information will provide most growers and Extension agents with the information they need to keep informed about soybean rust in the United States.

Also, daily updates on the movement of SBR can be found at http://www.sbrusa.net/. Forecasts for the movement of SBR can be found at http://www.ces.ncsu.edu/depts/pp/soybeanrust/.

A good site for soybean rust information is at www.ncpdn.org, which has links to other soybean rust sites of interest. If you go to this site, use the links on the left side of the page to go to first detectors, and then follow the link to Michigan. This site has two recent power point presentations on soybean rust, including one on fungicide use.

Another good source of information on soybean rust is: http://www.plantmanagementnetwork.org/infocenter/topic/soybeanrust/.

Farm Radio Network is a good resource for rapidly emerging events.

Growers should not change planting practices or varieties this year.

Early stages of rust are difficult to identify and distinguish from other soybean leaf diseases. Growers should rely on a person who has received training in the identification of SBR.

Wait for official confirmation of SBR from MSU Extension before applying any fungicides for SBR control. Applying fungicides too early could mean the difference between one and two applications. Other resources would be Ohio State University, Purdue University and the University of Illinois. They should be able to give Michigan an idea of how fast rust is moving north.

Most states are recommending a strobiluron (Headline, Quadris), a Triazole (ie Folicur, Domark, Bumper, Laredo, Propimax, Tilt) or a premix (Quilt, Stratego) for the first application. A strictly preventative spray such as a strobiluron applied by itself must be applied before the rust exceeds 2% of the leaf area in the lower canopy. Earlier is better, but not before rust in imminent. Too early, and the fungicide will not provide enough protection for later growth stages, possibly resulting in a need for a second fungicide spray. If rust exceeds 2% leaf area infection in the lower canopy, then apply either a triazole or a premix. Don’t let the rust move into the mid- and upper canopies before applying a control. Timing of the first fungicide application is critical to good control. More information on fungicides available for rust control can be found at: http://www.ca.uky.edu/agcollege/plantpathology/PPAExten/SoybeanRust.htm.

Soybean rust will not survive the Michigan or Midwest winters, it moves up from the south every year.

Be sure to know how to qualify for crop insurance payments.

Don’t panic, keep informed, and use official web sites and MSU Extension notifications for making your decisions, especially this first year when we don’t know what to expect from this disease.

Scouting
§      Especially critical for both the first and possible second fungicide applications.
§      Longevity of fungicide protection depends on many factors – weather, coverage, fungicide properties and plant age. It is probably in the range of 14 to 21 days for the strobilurons and triazoles.

General information 
§      Fungicide droplet size should be in the range of 200 to 250 microns.
§      Use a minimum of 20-25 gal of water per acre, and 5 gal for air application. Use double jet fans or two flat fans directed both forward and backward. In Brazil, the double jets provide better coverage than the cone fans.
§      Most rust infections occur during growth stages R3 to R5 in Brazil. We need to keep in mind that Brazil grows mostly determinant soybeans and in Michigan we grow mostly indeterminates.
§      Determinate type soybeans complete their vegetative growth prior to flowering and the main stem ends in a rather large terminal raceme (group of flowers along the stem). Indeterminate growth-type varieties continue to increase in height for several weeks after beginning to flower. Presently, all commercial soybeans grown in northern latitudes (MG 00 through IV) have an indeterminate growth habit, while those in the more southern groups V to VIII have a determinate habit.
§      After growth stage 6, rust should not affect yield. However, if SBR were to show up midway into GS 6, i.e. the beans have about 50 percent moisture, a fungicide might be needed if one was not applied within the past 15 days. This will depend a lot on the weather.
§      Sentinel plots are small plots of early planted and early maturing soybeans. Often soybean rust will show up in these plots first. Sentinel plots can also be early planted soybean fields with normal maturing soybeans, but which are scouted regularly. There will be 30 sentinel plots in Michigan. The purpose of the plots is to provide sites where intensive scouting for rust can be carried out and will also provide one source of data for the national map showing movement of the disease (www.sbrusa.net). The locations of the 30 plots were identified by MSU, MDA and the Michigan Soybean Promotion Committee. MSU Extension’s Mike Staton has already been in touch with many of you to assist in locating cooperators for many of these plots. MSUE will cover the scouting of 20 plots and MDA will do the rest. Each plot is 50 X 50 feet in size, and scouting will be carried out within the plots following a specific protocol. Plots will initially be scouted once a week and then every three to four days once forecasts and movement of the rust in states south of Michigan suggests that the infection may occur in the near future.

Cool weather and corn emergence

Kurt Thelen
Crop & Soil Sciences

The relatively dry and warm weather experienced in April has enabled many corn growers to get an early jump on corn planting. However, current forecasts are predicting a return to cooler and perhaps wetter conditions for the remainder of the month and into early May with daily highs in the mid-60s or less. How will this cool spell affect corn emergence?

For corn to emerge it takes the accumulation of approximately 100 GDD. To calculate daily GDD accumulation, average the daily high and low temperature and subtract 50. For example, if the daily high is 64 degrees and the nightly low 40 degrees, the daily GDD accumulation is [(64 + 40)/2] – 50 = 2 GDD.

As this example indicates, corn germination and emergence will be very slow until temperatures warm up. Barring any major change in the forecast, the early-planted corn may take more than three weeks to emerge. This type of slow corn emergence scenario is not new to Michigan growers. Modern corn genetics and seed treatments help corn withstand tough early season conditions and seem to help the crop get through the vulnerable pre-emergence period.

So, when is the best date to plant corn in Michigan? Of course, the answer varies from year to year, based on weather and field conditions. However, some generalizations can be made regarding date of planting that can be used for guidance.

Figure 1 shows a response curve based on net returns generated from a corn date-of-planting study conducted at MSU. Although the curve will shift from year-to-year depending on weather conditions, the shape of the curve is very typical for Michigan conditions, and it illustrates three important points regarding corn date of planting.

1)    There is a yield penalty for planting corn too early or too late.
2)    There is a relatively short “optimum” time period to plant corn.
3)    At some point in the planting season, it pays to shift from a full season hybrid to a short season hybrid.

Regarding point one, most varieties of corn will not germinate if soil temperature is below 50 degrees. As stated above, emergence and growth of young corn seedlings is temperature dependent and slows down considerably with cool temperatures. Planting too early increases the vulnerability of corn by slowing down the germination process and lengthening the vulnerable pre-emergence period. Additionally, very early-planted corn has a greater likelihood of being exposed to frost and cold temperature damage after emergence. Conversely, planting corn too late results in yield loss by limiting the amount of seasonal GDD’s available to produce yield and may result in higher grain drying costs in the fall.

Point number two, the relatively short optimum planting period, characterizes the dilemma facing corn growers. For much of Michigan, this optimum period is usually sometime around May 1. Because the optimum planting time period is short, most growers must plant some corn before or after the optimum planting date. In most years it is usually advantageous to err on the early side as opposed to the late side of the optimum planting date for the following reasons: on average the weather for the pollination period of early-planted corn is more favorable than the weather conditions for pollination of late planted corn; early-planted corn can take advantage of the longer day lengths for grain fill; early-planted corn is slightly shorter than late planted corn which can reduce lodging problems; and, early-planted corn will be dryer at harvest than late planted corn, thereby reducing grain drying costs. This leads us to point number three regarding switching from a full-season to a short season hybrid.

Because of our northern latitude, Michigan corn growers have a shorter growing season to work with than our southern neighbors. Therefore, we need to be especially cognizant of the relative maturity rating of corn. Research has shown that at some point in the later part of the planting season, it pays to shift from a late maturing, full season hybrid to an early maturing, short season hybrid. The basis for the cost effectiveness of switching to a short season hybrid is primarily in the ability to harvest dryer grain. Again, the optimum time to pull the trigger on the switch to a short season hybrid will vary from year-to-year depending on weather conditions, but it is generally around the third week of May for much of Michigan.

Loss of N from Urea

Darryl Warncke
Crop & Soil Sciences

I have received many inquiries about loss of nitrogen from surface-applied urea on wheat. Urea is broken down and converted to the ammonium (NH₄) form of nitrogen by the enzyme urease, which is fairly ubiquitous. During this process, the nitrogen goes through the stage where volatile ammonia (NH₃) can be lost into the air if there is not enough moisture to hold it in the ammonium form. Optimally there would be enough precipitation (0.25 inch or more) within a couple days after application to move the nitrogen into the soil where the ammonium will be attached to soil particles.

The key factors that influence volatile N loss from surface-applied urea are the surface soil temperature, soil pH, soil texture and soil moisture. If the soil surface is so dry that the urea does not readily dissolve, this will minimize loss. However, if there is sufficient moisture to dissolve the urea, but not enough to move it into the soil, then there is great potential for volatile N loss. In a study done a number of years ago in Illinois on a silt loam soil, pH 6.5, over a 10-day period about 10% of the N was lost from urea at 60°F and about 17% was lost at 75°F. In a similar study over a 10-day period about 25% N lost occurred at pH 6.5, whereas about 18% occurred at pH 6.0 and about 12% occurred at 5.5. At pH 7.0 the loss was near 35%. Volatile N losses also tend to be less on clayey soils than on sandy soils because of the higher cation exchange capacity to hold ammonium. These were constant temperature studies. Cooler temperatures at night will slow the loss. Most of the loss tends to occur during the first 10 to 14 days. After that the rate of loss levels off.

Predicting the amount of volatile N loss from surface applied urea is difficult. For urea that was applied more than two weeks ago (and no rain occurred) volatile N loss will most likely be at least 10 percent and could be as high as 25 percent. For those still waiting to apply urea, wait until the chance of measurable rain is good. Volatile N loss is primarily a problem from urea and does not occur from most other nitrogen materials. Urea-ammonium nitrate (28 % solution nitrogen) does contain 50% urea so loss can occur. Another option is to apply ammonium sulfate or mix ammonium sulfate with urea to reduce the potential for loss. Addition of urease inhibitors to the urea can effectively reduce the rate of urea break down for up to four weeks and thereby reduce the potential for volatile N loss.

At this point farmers have two options, apply an additional 25 pounds of N per acre (about $9 per acre plus time and spreading cost) or wait and see how the wheat looks in two to three weeks before deciding whether or not to apply additional N. With the dry soil conditions root growth has been somewhat limited and the wheat has not been able to effectively utilize N present in the soil. Some significant precipitation will improve this situation. A check of the nitrogen status of the wheat leaf tissue or an evaluation of the general greenness of the leaves in two to three weeks can be used as an indicator. Another approach is to spread an additional 25 pounds of N per acre now on a small portion of the field and then compare the applied and non-applied areas in two to three weeks. If there is a limited difference in growth and greenness between the general field area and added N area then applying additional nitrogen will likely not be beneficial. If there is a major difference in growth and greenness between the two areas, then applying additional nitrogen will likely be beneficial.

Weed management in wheat

Jim Kells and Kathrin Schirmacher
Crop & Soil Science

Each spring there are questions about the risks associated with 2,4-D or MCPA application to wheat past Feeke's Stage 6. Wheat tolerance of 2,4-D is highest between Feeke's stages 3 and 6 and is lowest in Feeke's Stages 9 and 10. Between stages 6 and 9, sensitivity to 2,4-D gradually increases as wheat growth stage advances. Thus, the risk of injury increases as wheat growth stage advances between stages 6 and 9. Severe injury is highly probable when 2,4-D is applied at Feeke's stages 9 and 10.

MSU recommends that application of 2,4-D to wheat be made after wheat has reached Feeke's stage 3 but prior to Feeke's stage 6. If growers choose to apply 2,4-D at later stages, they need to understand the associated risk. This risk can be minimized by applying the amine form of 2,4-D or reducing the rate of a 2,4-D ester. A much better alternative on wheat past Feeke's stage 6 is to use another herbicide with a wider application window that is effective on the weeds present in the field.

1)    Do not apply more than 20 lbs of nitrogen per acre in the form of 28% N when using a surfactant with herbicide.
2)    Do not apply more than 40 lbs of nitrogen per acre in the form of 28% N when no surfactant is used.
3)    Avoid high-temperature, high-humidity days. Late afternoon applications carry less risk of leaf burn.

Effectiveness of burndown herbicides for winter annual and perennial weed control in corn and soybeans

Jim Kells and Kathrin Schirmacher
Crop & Soil Science

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.

In some cases, it may be desirable to control these weeds several days prior to planting. With high weed density, excessive plant material can also interfere with seed placement and may slow planting. Also consider that the low soil moisture conditions we are currently experiencing may reduce herbicide activity on weeds. Table 1G and Table 2C (both in the 2005 Weed Control Guide for Field Crops E-434) list rates and effectiveness ratings for burndown herbicides in no-till corn and soybeans, respectively.

Weed control in non-GMO soybean

Christy Sprague
Crop & Soil Sciences

Even with the substantial number of Roundup Ready soybean acres in the state this year, there are several producers that will be growing non-GMO soybeans. Since some of these producers haven’t planted non-Roundup Ready soybeans for several years, there are a few pointers that should be remembered for effective weed control in conventional (non-GMO) soybeans.

1. It is important to start clean! As with all weed control strategies, starting with a weed-free seedbed is essential. This can either be done with tillage or an effective preplant burndown herbicide treatment. In no-till soybeans using an effective burndown treatment is particularly important since typical postemergence soybean herbicides will not adequately control typical no-till weeds. For adequate control of several of these no-till weeds, 2,4-D, glyphosate or a combination of the two should be used in the burndown treatment. When including 2,4-D ester in the burndown treatment, this application should be made at least one week prior to soybean planting.

2. Producers of non-GMO soybeans should also consider using a preplant or preemergence herbicide with residual activity as a foundation program for hard to control weeds such as common lambsquarters, common ragweed, giant ragweed and eastern black nightshade. Relying on a total POST program for control of these weeds can be difficult. Control of these weeds has also been difficult in Roundup Ready soybeans programs so it is important to control these species with a two-pass herbicide program. By waiting to control these weed with a total POST program many times these weeds can become too large, may be affected by the environment (hardened off by hot-day weather), or may just not be effectively controlled. Getting a start on controlling these weeds early in the season will insure greater overall success for your weed control program. Also using a two-pass program with a preplant or preemergence herbicide application limits the use of “rescue” herbicide treatments late in the season that can further stress soybean growth on previously injured soybeans.

3. Make timely POST applications. Many producers have been accustomed to controlling large weeds by increasing the rate of glyphosate in Roundup Ready soybean. Unlike glyphosate many of the POST herbicides used in non-GMO herbicides are not very effective on large weeds. It wasn’t too long ago when the application window for POST applications in soybean was between two and four-inch tall weeds. So, remember, when using a non-glyphosate based program herbicides need to be applied before weeds exceed four inches tall for adequate control. Applying a preplant or preemergence herbicide will also help extend this window by providing some early season control of these weeds.

4. Are herbicide resistant weeds a problem on your farm? There are several populations of ALS-resistant and triazine-resistant weeds around Michigan. If herbicide resistance has been a problem on your farm in the past, take this into account when planning your weed control strategy in conventional soybeans. For example, if you have ALS-resistant common lambsquarters relying on a POST program of Harmony GT or Raptor would not control this weed. However, there are several soil-applied herbicides that can effectively control common lambsquarters season-long. To determine the effectiveness of herbicides on common lambsquarters and several other weeds, consult the MSU Weed Control Guide for Field Crops (E-434).

For weed control in non-GMO soybean, I strongly recommend a two-pass program that consists of a preplant or preemergence residual herbicide followed by a postemergence program. Using a two-pass program with a residual herbicide may add to the overall cost of your weed management program but this program will result in overall more consistent control of several weed species.

Spring has sprung and weeds are emerging in sugar beet fields: Start scouting!

Christy Sprague
Crop & Soil Sciences

Similar to last season, early warm weather has brought on the emergence of several weed seedlings in planted sugar beet fields. Starting now, timely herbicide applications will be critical for effective weed control programs, particularly for growers who will be using micro-rates. Micro-rate herbicide applications can be a cost-effective strategy for weed control in sugar beets, but again timing is everything. The first micro-rate application should take place when weeds are less than 1/8-inch tall (cotyledon stage). If weeds get larger than ¼-inch, micro-rate applications are less effective and standard herbicide rates should be used.

Due to the dry conditions over the last couple of weeks, weed emergence may be ahead of sugar beet emergence in several fields. When scouting these fields, growers may be tempted to use glyphosate to control emerged weeds. I would strongly caution against this practice, particularly if the sugar beets have been in the ground over five days. Even though it appears that there aren’t any emerged sugar beets in the field, we have accumulated several growing degree days (GDD) and sugar beet seedlings may just be cracking through the soil surface. In the past, there have been instances of 50 to 80 percent stand reduction from glyphosate applications where it appeared that sugar beets hadn’t emerged yet. Where in fact these seedlings were just pushing through the soil surface and came into contact with glyphosate. If there is any question, it is safer to apply a micro-rate herbicide application to control the existing weed seedlings. Below are the general guidelines for timing micro-rate herbicide application using GDD.

For the remainder of the micro-rate applications, MSU research has shown applying micro-rates on a 225 GDD schedule has shown the most consistent weed control across species while reducing the potential for sugar beet injury. However, in fields with sandy or darker soils (high organic matter) and high weed pressures, it is suggested to check fields at 150 GDD and time applications for 175 GDD. For growers who want to adjust the timing of micro-rates relative to weed emergence, it may be possible to lengthen the spray interval early in the season (April) to 275 GDD when common lambsquarters is the predominant weed. In May this interval should be shortened to 225 GDD until pigweeds (redroot pigweed and Powell amaranth) start to emerge, then micro-rate applications should be made every 175 to 200 GDD.

GDD Formula = (High Temp + Low Temp)/2 - 34°F.

New options for weed control in soybean

Christy Sprague
Crop & Soil Sciences

Sequence 5.25EW is a new premix being marketed by Syngenta that is a combination of s-metolachlor (Dual Magnum) and the full-loaded K⁺ formulation of glyphosate (Touchdown Total). Sequence can be applied preplant and preemergence in conventional soybean and postemergence in Roundup Ready soybean. This premix is designed to control existing weeds and provide residual control of grasses and some small-seeded broadleaf weeds, including pigweeds and nightshade. Do not apply Sequence to emerged soybean unless soybean is designated Roundup Ready. Postemergence applications of Sequence in Roundup Ready soybean can be applied from soybean cracking up through the third trifoliate.

Under certain conditions, postemergence applications may cause soybean leaf crinkling or necrotic leaf spots. These symptoms are cosmetic and should not affect soybean yield. The postemergence use rates of Sequence range from 2.5 to 3.5 pts/A. A typical postemergence use rate of 2.5 pts/A contains 0.94 lb ai/A of s-metolachlor (0.98 pt/A of Dual Magnum) and 0.70 lb ae/A of glyphosate (21 fl oz/A of Touchdown Total). As with all glyphosate products, ammonium sulfate (AMS) should be added to improve the consistency of weed control. Postemergence applications should not exceed 3.5 pts/A in a single application or per season. If Sequence is applied preplant or preemergence, do not apply another s-metolachlor or metolachlor containing product postemergence to soybean.

Synchrony XP (mp) 28.4XP is a new premix formulation of chlorimuron (Classic) and thifensulfuron (Harmony GT) that can be applied preplant, preemergence or postemergence. Synchrony XP is an extruded paste formulation being marketed by DuPont that contains the same ratio of chlorimuron and thifensulfuron as Synchrony STS, but has a lower percentage of active ingredients so a higher rate of Synchrony XP is needed to equal the same amount of active ingredient in Synchrony STS.

Synchrony XP is being positioned as a replacement for Canopy XL burndown and preemergence applications in soybean. Synchrony XP is labeled at rates of chlorimuron comparable to Canopy XL. The use rates of Synchrony XP are 1 oz/A if the soil pH is between 7.1 and 7.6 and 1.25 to 3.0 oz/A if the composite soil pH is 7.0 or less. These applications should only be made to medium- and fine-textured soils with 1.5 to 4% O.M. and pH 7.6 or less. To compare Synchrony XP to Canopy XL, 1.1 oz/A of Synchrony XP would contain the same amount of chlorimuron as 2.5 oz/A of Canopy XL and 1.5 oz/A of Synchrony XP would contain the same amount of chlorimuron as 3.5 oz/A of Canopy XL.

Similar to Canopy XL, the benefits of the chlorimuron in preplant applications of Synchrony XP include residual control of several annual broadleaf weeds including pigweeds, common ragweed and velvetleaf. Additionally, chlorimuron aids in the burndown of a number of broadleaf weeds, particularly when combined with 2,4-D ester and/or glyphosate. To obtain maximum burndown activity, the addition of 1% v/v of crop oil concentrate is required and again the addition of 1 pt/A of 2,4-D ester is recommended (remember with 2,4-D ester a minimum of 7 days is needed between application and soybean planting). Unfortunately, since Synchrony XP contains two ALS-inhibiting herbicides, it won’t control of ALS-resistant marestail (horseweed), lambsquarters, pigweed or ragweed species. Additionally, eastern black nightshade will also not be controlled with Synchrony XP.

2005 Review of weed management options for dry edible beans

Christy Sprague
Crop & Soil Sciences

At the 2005 Bean and Beet Symposium, I presented a review of the different herbicide options currently available for weed control in dry edible beans. To help fill in the holes for those of you who were frantically taking notes and thought you may have missed something, this article is a summary of that presentation. In this article the estimations of herbicide costs were calculated from an average of three 2004 in-season herbicide price lists. For additional information on weed control in dry beans please consult the MSU Weed Control Guide for Field Crops (E-434).

Review of soil-applied herbicide options
Preplant incorporated ONLY

Treflan, pendimethalin (Prowl H₂O, Prowl, Pendimax) and Sonalan: Annual grass control is excellent with all three herbicides. Treflan and Sonalan provide better pigweed control than Prowl. Prowl and Sonalan provide better common lambsquarters control than Treflan. None of these herbicides will control eastern black nightshade or common ragweed. Eptam should be tank-mixed with each of these herbicides for additional annual grass and broadleaf weed control. The application rate of Treflan HFP is 1 pt/A (~$3.25/A); Prowl H₂O is 1.6 pt/A (~$5.75/A); Sonalan is 2 pt/A (~$6.00/A).

Eptam: Eptam provides excellent control of several annual grasses and good control of common lambsquarters. Eptam also will suppress common ragweed, wild mustard and nightshade species. Thus tank-mixing Eptam with Treflan, Prowl or Sonalan will improve control of these weeds. Eptam is applied at 1.25 qt/A (~$10.00/A). It is important to weigh these costs against the weed control benefits. If the Section 18 is granted for Reflex in the 2005 season, this would be a postemergence option for control of common ragweed and nightshade.

Pursuit Plus: Pursuit Plus provides fair control of common cocklebur, jimsonweed and smartweed and good-to-excellent control of several broadleaf and annual grass weeds. Common ragweed is not controlled. Pursuit Plus is typically applied at 20 fl oz/A (~$7.00/A). On heavy soils with more than 2% O.M. this rate can be increased to 30 fl oz/A.

Crop injury can occur from applications of Pursuit Plus. Precautions that need to be taken to avoid crop injury include: do not apply on sands or loamy sand soils do not apply if cold or cold to wet conditions are predicted one week after planting and remember that dry bean varieties can vary in their sensitivity to Pursuit, so keep this in mind when trying a new dry bean variety. Rotation restrictions are also critical with Pursuit Plus. These restrictions include 40 months and a bioassay for sugar beets, cucumbers and tomatoes; 18 months for oats; and 26 months for potatoes.

Alachlor (IntRRo, Micro-Tech): Alachlor provides excellent control of several annual grasses and good control of pigweed and eastern black nightshade. Alachlor should be incorporated in the top two inches of soil to minimize dry bean injury. Do not use alachlor on sands or sandy loam soils or injury can occur. Alachlor can be tank-mixed with Eptam, Prowl, Sonalan or Treflan for common lambsquarters control. Postemergence applications of a broadleaf herbicide may be needed for additional broadleaf weed control. IntRRo is typically applied at 2 qt/A (~$9.25/A).

Preemergence or Preplant Incorporated

Dual Magnum and Outlook: A preplant incorporated application of either Dual Magnum or Outlook minimizes crop injury compared with preemergence applications. Navy and black beans are more sensitive to Outlook than Dual Magnum. Dual Magnum and Outlook both provide good control of pigweed and excellent control of annual grass weeds. However, Outlook provides better pigweed and eastern black nightshade control compared with Dual Magnum. Dual Magnum and Outlook can be tank-mixed with Eptam, Prowl, Sonalan or Treflan for common lambsquarters control. Postemergence applications of a broadleaf herbicide may be needed for additional broadleaf weed control. The typical use rate for Dual Magnum is 1.33 pt/A (~$16.50/A) and Outlook is 14 fl oz/A (~$14.75/A).

Pursuit: Pursuit may be applied preemergence or preplant incorporated. Pursuit 70DG at 0.72 oz/A (~$7.65/A) can be tank-mixed with other soil-applied herbicides for additional broadleaf weed control and to control annual grasses. Remember, Pursuit will not control common ragweed. Similar to Pursuit Plus, crop injury can occur and precautions need to be taken to avoid injury. These precautions include: do not apply on sands or loamy sand soils, do not apply if cold or cold to wet conditions are predicted one week after planting, and dry bean varieties vary in their sensitivity to Pursuit applications. Rotation restrictions are critical with Pursuit. These restrictions include 40 months and a bioassay for sugar beets, cucumbers and tomatoes; 18 months for oats; and 26 months for potatoes.

Preemergence ONLY

Sandea: Sandea provides excellent control of pigweeds and wild mustard and good control of common ragweed and velvetleaf. Sandea is an ALS-inhibiting herbicide; so it will not control ALS-resistant weeds, such as ALS-resistant common ragweed. Sandea can be tank-mixed with Dual Magnum or Outlook for grass control. Application rates of Sandea range from 0.5 oz/A (~$18.00/A) to 0.67 oz/A. The lower use rate should be used on sandier soils. Dry bean varieties appear to vary in their sensitivity to Sandea. Kidney, pinto and great northern beans appear to be more sensitive to Sandea than other dry bean classes. The rotation restriction for Sandea to sugar beets is 21 months.

When looking at these different options there are a few things to consider when using these herbicides alone or in combination. One of the first things to consider is, “What are the weeds that need to be controlled?” These weeds will typically be ones that escape control from soil-applied herbicides and may include common ragweed, common lambsquarters and eastern black nightshade. Selection of an herbicide or combination of one or more of these herbicides will be dependent on the weed complex in the field (Table 1). When making these weed control decisions, it is important to consider certain guidelines, such as rotation restrictions, herbicide use rates, adjuvant selection, application timings and tank-mixtures with other herbicides.

Rotational restrictions: All postemergence broadleaf herbicides with the exception of Basagran, have rotational crop restrictions. Some of these restrictions may influence your herbicide selection, depending on your cropping system. For example, the rotation restriction for Reflex is 10 months for corn and 18 months for alfalfa, sugar beets, potatoes, cucumbers, canola and tomatoes. The rotation restriction for Raptor is 18 months for sugar beets (extended to 26 months if pH is less than 6.2) and canola. Pursuit’s rotation restriction is 40 months and a bioassay for sugar beets, canola, cucumbers and tomatoes.

Use rates: The use rate for Raptor is 4 fl oz/A (~$15.75/A) in edible legumes. For Reflex the use rate is 1 pt/A (~$12.00/A) and this can only be used once in a two-year period. Common ragweed less than 4-leaf will be controlled half pt/A of Reflex. Pursuit 70DG is generally used at 0.72 oz/A (~$7.65/A) and Basagran rates range from 8 fl oz to 2 pt/A (1.25 pt/A ~$12.00/A) depending on weed species, size, and herbicide tank-mixture.

Grass control: Raptor alone provides fair control of foxtails. Foxtail control is good when Raptor is tank-mixed with Basagran at 8 fl oz/A + NIS + 28%N (or AMS – ammonium sulfate). Barnyardgrass and crabgrass control are only fair. Assure II, Select, Arrow, and Poast can be tank-mixed with Basagran, Reflex, or Basagran + Reflex for grass control. However, do not tank-mix Assure II, Select, Arrow or Poast with Raptor or Pursuit, because grass control will be compromised.

Adjuvant selection: Basagran alone should be applied with 1 qt/A of a crop oil concentrate (COC). Reflex should be applied with a non-ionic surfactant (NIS) at 0.25 to 0.5% v/v or a COC at 0.5 to 1.0% v/v. Include COC when tank-mixing Basagran + Reflex. Raptor or Pursuit alone should be applied with 0.25% v/v of NIS. To increase control, 28% N at 2.5 gal/100 gal of spray solution or 12-15 lb/100 gal of spray solution of AMS can be added to Raptor + Basagran or Pursuit + Basagran applications. The addition of at least 8 fl oz of Basagran to Raptor or Pursuit will “safen” these applications. To control common cocklebur, jimsonweed or provide good control of common lambsquarters, increase the rate of Basagran to 16 fl oz when tank-mixed with Raptor and use COC + 28% N or AMS. Do not add 28% N or AMS when tank-mixing Raptor and Reflex.

Application timing: Raptor, Reflex, Basagran, or Pursuit should only be applied after dry beans have one fully expanded trifoliate. Do not apply these herbicides once dry beans start to bloom.

Rain-free periods: The rain-free period is one hour for Assure II, Select, Poast, Pursuit, Raptor and Reflex, and eight hours for Basagran.

Regional reports

2 – Southwest

Bruce MacKellar

Weather
What started out as a friendly soil moisture and surface water situation this spring has rapidly turned into one of the driest late March to mid-April periods on record over much of southwest Michigan. Rainfall totals have been running as much as three inches behind normal in some areas so far this year. The last significant rainfall in St. Joseph County occurred on March 19, at a half inch of precipitation. Soils changed rapidly from being saturated and at least partially frozen towards mid-March to being parched by April 20. Widely scattered thundershowers on April 19 and 20 missed most of the region, providing rainfall further to the east. The dry conditions have allowed producers to be on a record pace for completing tillage operations. While it has been dusty when fieldwork is taking place, cover crops on the majority of fields in St. Joseph County have really helped keep wind erosion down to a minimum this spring.

Commodity reports
Van Buren/Berrien ANR Educator Mike Staton reports that wheat is progressing well in those two counties. Recent warm temperatures have spurred growth well ahead of normal with most fields in the Feekes Stage 5 growth stage the earliest planted fields approaching Feekes stage 6. Most stands look good with shallow rooting being noted in some of the sandier fields.

Alfalfa plants have been responding well to the warm weather with many area fields approaching six to seven inches in height. It appears as if last spring/summer’s saturating rains took somewhat of a toll on stands in lower areas of fields. Flooding induced stand loss can be found in fields with “topography” where water stood for significant periods. However, these areas are usually quite small and should not cause much yield loss overall. Mike Staton reported that an alfalfa seeding with three different planting dates ranging from late August to mid-September showed marked differences in winter survival rates. This shows once again that delaying planting into September can cause reduced stands in alfalfa seedings. In fields scouted in Van Buren, Cass and St. Joseph counties on April 20, there were no signs of alfalfa weevil at this time. With cooler temperatures predicted for the next 10 days, the development of the crop and the weevil may be slowed down substantially.

Growers have been busy planting corn in many areas. Some corn probably went in as early as April 15. The majority of the crop that has been planted went in within the last few days. Some areas may be as much as 20 percent planted with commercial corn at this point. With soil temperature highs in the mid-60s recently, some corn may be approaching spike soon if there was adequate moisture for germination. Cold temperatures in the forecast will slow down growth and development, and most likely planting, in the region. Tillage occurred early enough this year to keep a lot of winter annuals from obtaining much growth. This should be a positive factor in reducing the potential for black cutworm larval damage in corn this year.

Seed corn planting is scheduled to begin shortly after May 1.

Many producers took advantage of the warm soil temperatures and dry moisture conditions to plant at least some of their soybeans early. I would peg the percentage of soybeans planted at five to ten percent. This number is probably highest in St. Joseph County. With colder weather in the forecast, the beans are better off under the soil surface.

Potato planting is well underway in St. Joseph and surrounding counties.

3 – West Central

Fred Springborn

Weather
April has started out very warm, mild and dry. A generally welcomed half-inch of rain fell on Tuesday night/Wednesday morning. Low soil temperature have climbed above 50°F at the Montcalm Research Farm, but the question is, “Will they stay that high?” Air temperatures have been in the low 60s F to the mid 70s F for afternoon highs.

Commodity reports
Oat planting is nearly complete. Wheat has broken dormancy and is greening up nicely. Some areas of fields did experience some winter kill but these areas are generally small.

Alfalfa has also broken dormancy. New seedings are being planted, and limited winter damage has been observed so far.

Sugar beet planting is rapidly progressing and is near complete.

Several corn planters have been in the field. Approximately 5 to 10 percent of the crop is planted.

4 – Central

Paul Gross

Weather
The region received about one half inch of rain Tuesday night and Wednesday (April 19-20). Temperatures reached the low 80s on Wednesday. The rain was welcomed to relieve dry topsoil conditions and will aid the slow growth of wheat and alfalfa this spring. Soil temperatures mid-morning on Wednesday were 54°. We expect that to go down as cooler weather is predicted over the next several days.

Commodity reports
This regional reporter has been cleaning the egg off his face after reporting in the last issue that there was little or no evidence of winter injury in the wheat and alfalfa crops. As temperatures warmed up and the crops broke dormancy it was very evident that we experienced moderate to severe winterkill in alfalfa and winter wheat. Many of the worst fields have been worked up and or replanted. Farmers that need large quantities of forage for livestock need to make the appropriate plans to cover those needs with corn silage or alternative crops.

The oats and new alfalfa seeding are planted with some beginning to emerge.

Corn is about 25 percent planted. Some farmers are nearly finished planting corn. Some farmers have done most of the tillage and are waiting to plant. There are a few fields of soybeans that have been planted.

Sugar beets are all planted and micro rate herbicide applications will begin soon.

5 – Thumb

Mark Seamon

Weather
Summer-like conditions of temperatures in the 80s and low humidity have really dried out many fields. Some areas have surface soil that is getting very dry. Two- to three-tenths of an inch of rain fell through most of the area on Wednesday morning (April 20). This was a welcome change to limited precipitation in the past few weeks.

Commodity reports
Alfalfa plants are showing nice new growth in many areas.

Farmers with early planting opportunities have most (95%) sugar beets planted. Planting conditions have been good in most areas. Some growers were concerned with dryness of soil around the seed at planting. Emergence is pretty good with variability caused by dry soil that has delayed germination.

Winter injury is showing up in many wheat fields. Patches of dead wheat can be found by quick glance while other dead plants are scattered throughout the field. Dry surface soil has limited the availability of nitrogen to most wheat. Root growth is limited in many fields, even where top growth looks good.

Early planting of about 10 percent soybeans has been done at this point. Since many growers are using treated seed, they have more confidence in early planting.

Major weather changes in progress

Jeff Andresen
Agricultural Meteorology
Geography

Following four weeks of record-level dry and warm weather since the last week in March, major changes in jet stream flow across North America are underway. This weather will lead to much cooler conditions for the upcoming week and possibly longer. The strong upper air ridging pattern that has been entrenched across the Great Lakes region is currently weakening and on its way eastward into the North Atlantic. In its place, a troughing pattern will develop, allowing a series of cold, Canadian-origin air masses into the eastern United States.

In the short term, high pressure will lead to sunny and dry conditions statewide on Thursday (April 21), with daytime temperatures reaching the upper 50s to low 60s. Friday through Sunday, a gradually intensifying area of low pressure will move from the Ohio Valley northward into southern Ontario, bringing widespread precipitation, wind and colder temperatures. The precipitation will begin in southern sections of the state late Friday as rain, but as northeasterly winds increase and colder air over Ontario moves into Michigan, will mix with or change to snow by Saturday morning. Saturday and Sunday are both likely to be unusually cold and wintry, with occasional snow or snow and rain mix (mainly in southeastern sections) and daytime temperatures remaining in the 30s in most sections. Nighttime temperatures will range from the low 20s far north to the low 30s far south.

While this weather system will definitely bring at least a temporary end to spring fieldwork and planting operations, it will also likely end topsoil dryness in areas missed by Wednesday=s rain event. Precipitation totals over the next three to four days will likely approach or exceed one inch in some spots across the southeastern Lower Peninsula, decreasing to around 0.25 inch or less in far northwestern sections of the state. Early next week, look for cool, mostly cloudy and blustery conditions to continue with the chance for scattered, mainly afternoon and early evening showers each day. Temperatures will moderate slightly after the weekend but still remain below normal with daytime highs Monday through Wednesday ranging from the upper 40s north to the upper 50s south and low temperatures falling back to the 30s. Look for mean two-inch bare soil temperatures to fall back at least 5-10 degrees F from recent levels by the middle of next week. Early morning frost or freezing temperatures will be likely over much of the state during the next several days. We are approaching the normal date of last spring freeze in a few higher elevation lakeshore spots in southern Lower Michigan, while most of the state experiences its last freezing temperatures in the first couple of weeks of May.

Further ahead, the upper air troughing pattern mentioned above is expected to dominate weather patterns across central and eastern sections of North America for much of the next one to two weeks, leading to a prolonged period of below normal temperatures in Michigan. The latest NOAA Climate Prediction Center 6-10 Day and 8-14 day outlooks (for April 26-30 and April 28 through May 4) both call for a below normal temperatures state- and region-wide. With most weather systems remaining south of Michigan, precipitation totals during both periods are forecast to remain at below normal levels. It is also worth noting that forecaster confidence in this outlook is much greater than normal for the season due to strong agreement among the various forecast tools.