May 3, 2007

In this issue

§      Management of glyphosate-resistant horseweed (marestail)

§      Glyphosate-resistant horseweed confirmed in Michigan

§      Micro-rate herbicide applications need to be timely in sugar beets

§      Exercise patience in deciding when to resume field operations

§      Sulfur and nitrogen starter fertilizer in Michigan corn

§      Manganese deficiency in winter wheat

§      Management of Fusarium head blight (scab)

§      Regional reports

§      Weather news

 

Management of glyphosate-resistant horseweed (marestail)

Christy Sprague
Crop & Soil Sciences

Earlier in this week’s issue of the Field Crop CAT Alert, Steve Gower with MSU Diagnostic Services reported 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.

Glyphosate-resistant weeds are not new to the United States. Currently, there are seven different weed species that are resistant to glyphosate. In fact, the first weed was a horseweed (marestail) population that was confirmed glyphosate-resistant in 2000 in Delaware. Since this first discovery, glyphosate-resistant horseweed has been found in 15 states with Michigan now being added as number 16. Our diverse cropping systems, I believe has helped us slow down the development of glyphosate-resistant weeds. However, now that we have resistance, there are several steps we need to do to manage resistant weeds and to further reduce the spread of glyphosate-resistance.

Earlier in Steve’s article, you learned that the horseweed population that was confirmed glyphosate-resistant was from a Christmas tree plantation in Mason County, Michigan. Repeated use of glyphosate to control weeds in this plantation was the main cause in the development of resistance. Even though Mason County is not a large county for agronomic crops, if resistance can be found in this county it may be present in other counties in Michigan. Possible other areas where we may have glyphosate-resistant horseweed are counties where no-till crop production is high and glyphosate is used exclusively for weed control. While resistance may not yet be present, following the practice of continuous glyphosate use without other weed control strategies will most likely lead to the development of glyphosate-resistance. So, how do we slow down the development of glyphosate-resistant weeds?

Diversity is the key. Whether it is diversity in tillage, herbicide use or cropping systems, diversity is one of the main strategies to slowing down the development of glyphosate-resistant weeds. Here are six main strategies that should be followed to help reduce the development of glyphosate-resistant weeds.

§      Rotate glyphosate with herbicides that have different modes of action.

§      Apply a residual herbicide before glyphosate or tank-mix another herbicide with glyphosate.

§      If glyphosate is used as a burndown treatment and in-crop in the same year, tank-mix the burndown glyphosate treatment with an herbicide that has a different mode of action.

§      Scout for changes in weed populations

§      Use cultivation and other mechanical weed management practices, when appropriate.

§      Use recommended rate for the appropriate weed height.

Management of glyphosate-resistant horseweed

Many of the strategies that are used to reduce the development of glyphosate-resistance can also be used to manage glyphosate-resistant weeds. However, unlike other weeds, even if you follow the strategies to reduce the development of glyphosate-resistant weeds you may find glyphosate-resistant horseweed in your fields. The main reason for this is that horseweed seed is wind-blown and can blow in from other sources. In fact, a recent paper in Weed Science strongly suggests that horseweed seeds can enter the planetary boundary layer, where long-range transport is possible. In addition, we also have several horseweed populations in Michigan that are resistant to ALS-inhibitors. Since the only effective POST herbicides that can be used in soybeans are ALS-inhibitors and glyphosate, control of horseweed can be extremely difficult post-emergence in soybeans.

Key principles to horseweed management

§      To effectively manage horseweed, it is important to control horseweed prior to planting.

§      2,4-D ester should be included in the burndown application. (Remember, a minimum of 7 days is needed between the application of 1 pt/A of 2,4-D ester and soybean planting.)

§      Horseweed is most susceptible in the rosette stage (less than 2-inches in height).

§      Herbicides should be applied before plants are 4 to 6 inches in height.

§      Spring burndown applications with residuals will help prevent new emergence of horseweed.

For more information and specific herbicide recommendations there is a fact sheet on Controlling Horseweed on page 167 in E-434, 2007 Weed Control Guide for Field Crops. Also visit www.glyphosateweedscrops.org to view a regional bulletin on the biology and management of horseweed.

Glyphosate-resistant horseweed confirmed in Michigan

Steven Gower
MSU Diagnostic Services  

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.

For the past several years, MSU Diagnostic Services has been screening horseweed populations for glyphosate, ALS, triazine and PPO resistance utilizing greenhouse whole plant assays. ALS-resistant horseweed has been documented in 35 field crop locations and seven Christmas tree plantations spanning 14 Michigan counties. Triazine-resistant horseweed has been documented in two field crop locations, 12 Christmas tree plantations and 4 blueberry plantations spanning five Michigan counties.

While glyphosate resistance was suspected by the growers in some of these populations, herbicide resistance proved not to be the case until now. The initial greenhouse screen of this Mason County horseweed population yielded survivors of glyphosate at 1X and 4X the labeled rate (22 and 88 oz/A Roundup WeatherMAX 5.5L, respectively, plus AMS at 17 lbs/100 gallons). These plants were stunted and delayed in development, but were able to bolt and produce seed. Seed was collected from these survivors and subsequent dose response experiments were established with the original field population and greenhouse population.

Horseweed plants were treated with glyphosate at 0.01X, 0.1X, 0.25X, 1X, 4X, 10X and 100X the labeled rate (0.22, 2.2, 5.5, 22, 88, 220, and 2200 oz/A Roundup WeatherMAX 5.5L, respectively, plus AMS at 17 lbs/100 gallons) when rosettes were 2 to 3 inches in diameter. Visual weed control ratings and dry weights were taken 21 days after treatment.

While GR50 values have not yet been tabulated, these experiments consistently show the ability for this population to survive glyphosate at 1X, 4X and occasionally 10X the labeled rate. The attached picture shows representative plants for each treatment and population.

Testing for herbicide resistance

If herbicide resistance is suspected in any weed species, samples may be submitted to MSU Diagnostic Services for a resistance screen. In most circumstances, a whole plant pot assay established from seed will be the standard test for herbicide resistance confirmation. Mature, high quality seed or seedheads should be collected from suspicious plants in late summer or fall and submitted in a paper bag or envelope. Do not seal plants or seed in plastic!

Generally, fees associated with herbicide-resistant weed testing are $50 per sample per herbicide site of action (i.e. ACCase inhibitors, ALS inhibitors, Photosynthesis inhibitors). Each additional site of action is $20 per sample. However, costs associated with horseweed samples submitted by Michigan soybean producers are covered by check-off dollars through the Michigan Soybean Promotion Committee. Samples submitted from out-of-state producers are $75 per site of action and $30 for each additional site of action.

Please contact Steven Gower (517-432-9693, sgower@msu.edu) with any questions regarding resistance confirmation or sample collection. Samples can be mailed to:

Michigan State University

Diagnostic Services - Attn: Steven Gower

101 Center for Integrated Plant Systems

East Lansing, MI 48824-1311

Micro-rate herbicide applications need to be timely in sugar beets

Christy Sprague
Crop & Soil Sciences

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. Missed timings early in the season can cause major weed problems as the season progresses. So, what are some of the options that can be done to control these weeds if a micro-rate application timing is missed? Below are some general guidelines that should be considered in choosing alternative weed control strategies if a micro-rate application timing is missed before the weeds become too large and require hand labor.

Factors to consider

Know the size of the weeds in the field. Your decision on what to do next for weed control is primarily going to be based on weed and sugar beet size. Weed species like common lambsquarters and velvetleaf are going to be the primary driver weeds this time of year. Five different weed control strategies are listed in this article that are dependent on weed size. See these different options below for each weed size (Option A, 1/8 inch tall weeds; Option B, Option C, or Option D, 1/4 inch tall weeds; and Option E, 1/2 inch tall weeds).

Was a pre-emergence (PRE) herbicide used on this field? If a PRE herbicide was used, this could impact the susceptibility of the weeds, as well as the potential susceptibility of sugar beets to increased injury. This factor should be considered when deciding on what weed control strategy to use. With cool-wet conditions, both weeds and sugar beets will be more susceptible to POST herbicides, particularly if there was a PRE herbicide applied. Keep this in mind when applying higher Betamix rates or when switching to a standard split herbicide program. Also, if a PRE herbicide was banded, check to see if there are any weeds emerging in the band. If weed control is good in the band, cultivation may be all that is needed.

Options

Option A: Weeds are 1/8 inch tall.Even if the maximum number of GDDs has passed for your micro-rate application schedule (generally around 225 GDD34), and weeds are still less than an 1/8 inch (0.125 inch) tall, continue using a standard micro-rate herbicide program. This may be the case with some of the slower growing early summer annual weeds.

Option B: Weeds are 1/4 inch tall. One option when weeds exceed the maximum size for a standard micro-rate herbicide application is to increase the rate of Betamix to 12 fl oz/A or 16 fl oz/A in the micro-rate application. According to the label, the rate of Betamix at 16 fl oz/A should only be increased if the smallest beets in the field are in the 4-true leaf stage. Increasing the Betamix rate may help control slightly larger weeds. Applications can be made later in the day to help reduce sugar beet injury. Also use caution when using higher Betamix rates if sugar beets are in the early 2-leaf stage. Sugar beets are more sensitive to stresses at this stage of growth.

Option C: Weeds are 1/4 inch tall.Another option is to make the standard micro-rate herbicide application when conditions allow and then shorten time period before the next application. For example, if the second micro-rate application timing is delayed, you may want to decrease the amount of time between the second and the third application. Larger weeds that are injured may be more susceptible to the third micro-rate application and won’t have completely recovered. Remember, sugar beets will also be more susceptible and that could potentially lead to an increase in sugar beet injury or stunting, especially if conditions are cool and wet. According to research we conducted last year, we were able to achieve better common lambsquarters control with this strategy compared with simply increasing the Betamix rate. In our research, we shortened the interval to approximately 75 GDD, which was approximately 5 days between the applications early in the season.

Option D: Weeds are 1/4 inch tall.Yet another option when the micro-rate herbicide application timing has been missed, is to switch to a standard split low rate herbicide application. If you choose to switch to a standard split herbicide application, do not add MSO or surfactant to this application. Applications should also be made after 4:00 PM. to reduce sugar beet injury. If weed control is adequate after the standard split application, growers can switch back to a micro-rate herbicide program (start GDD accumulation after the standard split application) or continue with a another standard split rate later in the season. This strategy was also more effective than simply increasing the Betamix rate for common lambsquarters control.

Option E: Weeds are 1/2 inch tall.If weeds reach 1/2 inch tall, it is best to plan on a standard split rate herbicide program. Apply the first split rate when sugar beets are less than the 4-true leaf stage. Weeds that are not completely controlled by this application will be controlled by the second application. The second application should be made 7 to 14 days after the first application. In most cases this is generally between 350 and 400 GDD. Applications of standard split rates should be made after 4:00 PM to reduce sugar beet injury.

Exercise patience in deciding when to resume field operations

Kurt Thelen
Crop & Soil Sciences

The recent extended period of rainy weather has growers anxious to get back on the tractor and planting corn again. Relatively wet and cool weather in late April has delayed corn planting relative to the past few years. Fortunately, modern planting equipment allows for rapid planting once fields finally dry out. I heard a grower remark once that with current modern farm machinery, “the entire state of Michigan can be planted in about one week’s time.” The operative word is patience when deciding when to restart field operations. The potential yield loss from planting in fields that are too wet far outweighs the potential yield loss from delaying planting until field conditions are suitable.

Planting in wet conditions often results in sidewall compaction of the seed furrow. This causes poor seed to soil contact, which has several negative consequences including: reduced germination and poor stands; uneven emergence, which reduces yield due to plant-to-plant competition; and restricted root growth, which compromises the plant’s ability to withstand moisture stress later in the growing season. In addition, the limited rooting can result in phosphorus deficiency even though soil test phosphorus levels are adequate. This occurs because the plant uses all of the phosphorus that is immediately available within the seed furrow. The roots of these plants will appear thickened and gnarled – a visual sign of compaction. After a period of time, roots may break through compacted seed furrow sidewalls and into the soil profile. As this occurs, initial phosphorus deficiency may be overcome and the plant will begin growing normally again. However, sidewall smearing and compaction will likely set the crop back by a week or more as it struggles to overcome the less than optimum soil environment.

Corn hybrids have a limited ability to advance through growth stages faster when planted later than their optimum planting date. Research at Michigan State University has shown that late-planted corn will progress through vegetative and reproductive development stages slightly faster relative to the same hybrid when planted earlier. However, this assumes that the hybrid’s relative maturity is acceptable for your maturity zone. The MSU hosts a website featuring local data (http://enviroweather.msu.edu) that can be accessed to determine average growing degree day (GDD) accumulations for your part of the state. Work with your seed dealer to determine which hybrids can reasonably be expected to mature in your area.

Research has shown that under average Michigan conditions, it generally pays to switch to a short season hybrid in late May. The basis for the cost effectiveness of switching to a short season hybrid is primarily in the ability to harvest dryer grain in the fall. 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 to fourth week of May for much of Michigan. The website referenced above can be used to determine the average remaining GDD’s left in the growing season when determining what the relative maturity of your short season hybrid should be.

In summary, the take home message is to not resume planting if soil conditions are too wet. There is still adequate time in the growing season to establish a good crop.

Sulfur and nitrogen starter fertilizer in Michigan corn

Ron Gehl
Crop & Soil Sciences

The recent decreases in atmospheric S deposition, increases in corn yields, and relatively early corn planting dates have prompted grower and industry interest in the use of S-containing starter fertilizer sources for corn. Six S-starter study locations were evaluated in Michigan in 2005 and 2006, including two sites per year on MSU research farms and the remaining four on producer fields. Sites were located on coarse-textured soils with a minimum or no-till cropping system. Treatments consisted of iterations of starter fertilizer with and without S addition (as ammonium sulfate, ammonium thiosulfate, or gypsum) and were replicated three or four times (Table 1). Plant height, chlorophyll meter readings and plant tissue samples were collected at approximately V4, V6 and R1.

 

Table 1. Starter fertilizer treatments at study locations in 2005 and 2006.

Ingham, Montcalm,

Saginaw, Clinton

Clinton

Berrien

Monroe

Lapeer†

Tuscola

Study year(s)

2005, 2006

2005

2005, 2006

2005, 2006

2005

2006

- - - - - - - - - - - - - - - - - - - - - - - - - lbs/ac - - - - - - - - - - - - - - - - - - - - - - - - -

Control

-

-

-

-

-

25N

-

-

-

60N

25N

25N+25P

25N+25P

133N+46P

15N+52P

-

-

25N+5S

25N+5S

136N+46P+5S

15N+52P+5S

64N+5S

25N+5S

25N+10S

25N+10S

138N+46P+10S

15N+52P+9S

69N+10S

25N+10S

25N+20S

25N+20S

143N+46P+20S

15N+52P+16S

67N+20S

25N+20S

25N+25P+10S

-

-

-

-

-

10S

-

-

-

-

-

† Treatments were applied at sidedress rather than as starter.

 

Analysis of the relative leaf chlorophyll content at the research farm sites revealed differences in leaf chlorophyll (greenness) among treatments, particularly at the V6 stage or earlier. Though differences were evident, the only distinguishable trend was that the gypsum treatment (10S) typically had less relative chlorophyll than most other treatments, except the control. Significant differences in plant tissue N and S among treatments were also identified in 2005 and 2006. Where differences were noted, the consistent trend was that the percent of N was less for the control and 10S treatments, as could be expected with the ammonium-based sulfur source, and the percent of S was less for the treatments without S.

Correct interpretation of the yield response data to fertilizer treatment is critical to diagnosing actual crop response to starter fertilizer containing S. Data collected at the research farm sites in both 2005 and 2006 indicate that rather large differences in yield (22 bu/ac and 23 bu/ac at Ingham in 2005 and 2006, respectively) occurred as a result of fertilizer treatment (Table 2). However, the lowest yielding treatment at all sites where a treatment response occurred (Ingham 2005 and 2006, Montcalm 2006) was the control, which received 0 starter fertilizer. At the research farm sites in either year, there were no significant differences in yield among any of the treatments that included some form of starter fertilizer. There were no trends in the data indicating that there was a significant response to the addition of S in the starter fertilizer.

 

Table 2. Corn yield response to starter fertilizer treatments including sulfur, nitrogen, and/or phosphorus at research sites in 2005 and 2006.

 

2005

 

2006

Treatment

Ingham

Saginaw

 

Ingham

Montcalm

lb/ac

 - - - - - - - - - - - - - - - - - - bu/ac - - - - - - - - - - - - - - - - - -

Control

161b

189

 

140b

198b

25N

 178ab

191

 

160a

 207ab

25N+25P

 172ab

194

 

163a

 207ab

25N+5S

 174ab

193

 

158a

 208ab

25N+10S

 168ab

192

 

158a

211a

25N+20S

183a

189

 

158a

 208ab

25N+25P+10S

 176ab

188

 

159a

 208ab

10S

 165ab

189

 

142b

 200ab

LSD0.05

 21

NS

 

15

 12

 

Yield data collected at the on-farm sites indicated that a significant difference in yield resulting from S addition to starter fertilizer treatment was evident at 3 of 7 sites across both years (Tables 3 and 4), and at only 3 of 11 sites when the 25N and 25N+xS treatments at the research farm sites were included in the analysis. The only site that showed a positive response to S addition relative to the N-only starter was Monroe in 2005, where the 25N+20S treatment yielded greater than the 25N-only treatment (189 bu/ac vs. 174 bu/ac). The other two significant site years (Berrien 2005 and 2006) showed a yield decrease for 25N+20S compared with the 25N+5S. This decrease was likely a function of seedling damage stemming from placement of the starter fertilizer with additional ammonical N 2-4” directly below the seed.

 

Table 3. Corn yield response to nitrogen and sulfur fertilizer applied as a starter at planting in 2005.

 

Location

Treatment

Ingham

Saginaw

Berrien

Clinton

Monroe†

Lapeer‡

lb/ac

- - - - - - - - - - - - - - - - - - - - - - bu/ac - - - - - - - - - - - - - - - - - - - - - -

25N

178

191

 151ab

149

174b

157

25N+5S

175

193

152a

155

 175ab

163

25N+10S

168

192

 150ab

158

 175ab

161

25N+20S

183

189

144b

157

189a

163

LSD0.05

NS

NS

7.0

NS

14.3

NS

† Actual applied S rates were 4.4, 8.8, and 12.7 lb S/ac.

‡ Treatments were applied sidedress at V4-V6 leaf stage.

 

 

Table 4. Corn yield response to nitrogen and sulfur fertilizer applied as a starter at planting in 2006.

 

Location

Treatment

Ingham

Montcalm

Berrien

Monroe

Tuscola

lb/ac

- - - - - - - - - - - - - - - - - - bu/ac - - - - - - - - - - - - - - - - - -

25N

160

207

 165ab

214

184

25N+5S

158

208

172a

213

187

25N+10S

158

210

 165ab

214

192

25N+20S

158

208

157b

216

192

LSD0.05

NS

NS

8.2

NS

NS

 

The yield responses observed in this study can primarily be attributed to the use of N, P or a combination of N- and P-containing starter fertilizer in general, rather than from the addition of S to the starter fertilizer blend. As atmospheric sulfate deposition continues to decrease, a corn yield response to sulfur is more likely to occur. Sulfur research in other Midwest states is showing hit-and-miss responses to S additions, with some positive yield results reported from states including Ohio, Iowa and Minnesota. For Michigan minimum or no-till cropping systems, particularly on soils with low OM, a response of S addition to a starter fertilizer is possible, but not probable. The likelihood of response should increase in cool, wet springs where mineralization is minimized and early crop growth is slowed. If growers elect to include S in their starter fertilizer program, soluble S sources (e.g. ammonium sulfate, ammonium thiosulfate) should be selected rather than elemental S, which may not be available to the growing crop in a timely fashion.

Manganese deficiency in winter wheat

Ron Gehl
Crop & Soil Sciences

Many stands of winter wheat in the state have taken a good beating this spring due to early growth followed by a mid-April cold spell. The variable weather affecting wheat growth has also prompted the appearance of manganese (Mn) deficiency in some fields. Manganese deficiency is the most common micronutrient problem in Michigan, and wheat is highly responsive to Mn. Manganese exists in many forms in the soil, most of which are unavailable to the growing crop. An adequate level of Mn2+, the primary plant-available source in our soils, is influenced closely by soil pH. Manganese issues most often occur on organic peats or mucks with pH >5.8, but can occur on mineral lakebed and glacial outwash soils with pH > 6.5. Manganese deficiency in wheat generally shows up in patchy areas within a field, and appears as generally stunted plants with yellowing of the upper leaves, slight striping of the leaves and whitish or colorless spots. In some wheat fields, sprayer or tractor tracks will appear noticeably healthier through an area of Mn deficient plants. This phenomenon results from the slightly compacted, more anaerobic (wetter) conditions under the tracks where bacteria convert Mn oxide to plant-available Mn2+. Often times, Mn deficiency shows up early in the spring as a result of limited root activity from environmental conditions (weather, compaction, disease, N deficiency, etc.), even though there may be sufficient Mn2+ in the soil. If limited root growth is driving the deficiency, the crop will often grow out of the Mn deficiency when conditions become more favorable. If you’re not willing to wait and see, foliar applications of Mn fertilizer can be effective at correcting the deficiency. Spray grade carriers of Mn sulfate are the recommended source, applied at a rate of 1 to 2 lbs of actual Mn per acre with 30 gallons of water and a sticker. (Always be sure products are compatible prior to tank mixing.) Chelated sources of Mn generally tank mix better, but are much more expensive and are generally no more effective than inorganic sources.

A detailed discussion of Mn deficiency in wheat, including deficiency photos, can be found at:

http://www.omafra.gov.on.ca/english/crops/field/news/croppest/2005/04cpo05a2.htm

Management of Fusarium head blight (scab)

Diane Brown-Rytlewski and Willie Kirk, Plant Pathology
Martin Nagelkirk, MSUE Sanilac County

This information is available as a fact sheet on the Field Crops AoE website at: http://fieldcrop.msu.edu/documents/FHB%20fact%20sheetmn.pdf

Fusarium head blight (FHB), commonly called head scab, is caused by several species of fungi in the genus Fusarium. It causes premature bleaching of spikelets and infected spikelets may be sterile. Grain from infected heads may be chalky white to pink, shriveled and light in weight. FHB is capable of causing a loss of grain yield, but the most significant financial losses result from the mycotoxin deoxynivalenol (DON or vomitoxin), which the fungus produces within infected kernels.

Managing FHB and DON can’t be achieved by any single control measure, but an integrated approach will give the best results.

Weather effects

The severity of FHB depends mostly on weather conditions. Rainfall and moderately warm temperatures at the time of flowering are most conducive to the development of the pathogen and the single best basis for disease prediction. However, rainfall prior to flowering encourages the development of the pathogen’s spores and moist conditions following infection of the flowering heads favors the production of DON. A model predicting the risk of scab can be found at: http://www.wheatscab.psu.edu/. The model uses temperature and relative humidity for the seven day period prior to flowering to predict the risk of an epidemic. Michigan-specific comments relative to wheat development, scab and foliar diseases can be found by clicking on the map icon and selecting Michigan.

Crop rotation and residue management

Residue from corn and wheat is the source of inoculum for FHB, so wheat should not follow a wheat or corn crop. Incorporating these residues into the soil may help reduce the production of inoculum. Varying wheat varieties and planting dates to spread the time of flowering may reduce risk by limiting the exposure of a grower’s entire crop to weather conditions favorable for FHB at this critical stage.

Varietal resistance

Although efforts to develop wheat varieties with resistance to FHB continue, most varieties currently grown in Michigan are moderately to highly susceptible to FHB. There are only a few winter wheat varieties with appreciable scab resistance. However, where available, planting a moderately resistant variety instead of a susceptible one can reduce FHB by 60 percent and DON by 40 percent. Michigan State University’s annual variety trial results for wheat include FHB ratings and can be found at http://www.css.msu.edu/varietytrials/wheat/.

Fungicide applications

Fungicide applications need to be made during the early flowering stage to maximize effectiveness.

A timely and thorough application of tebuconazole has been shown to reduce the severity of FHB by at least 50 percent. However, the application’s impact on DON is less predictable. Experience from commercial fields suggests that the use of tebuconazole may reduce DON by 0.5 to 1 ppm, though research has shown that fungicide’s effect on DON levels can be more significant under severe disease pressure. For 2007, three tebuconazole products are registered in Michigan under a special Section 18 emergency exemption: Folicur 3.6 F, Muscle 3.6 F and Embrace 3.6 L. All three of the labels allow a single application of tebuconazole to be made up to Feekes 10.5.1, the beginning of flowering. In addition to tebuconazole, a new fungicide, Proline (prothioconazole) has been registered in Michigan for use on wheat to control FHB and foliar diseases of wheat. It is labeled for use up to Feekes 10.5.2 (50 percent flowering).

For best results, the fungicides should be applied 1 to 3 days after 75 percent of the wheat is fully headed (the entire head has emerged beyond the flag leaf). Depending on temperature, this timing often corresponds to when 25 percent or less of the heads have begun to flower.

Application technology

When using ground equipment, the boom height should be adjusted to target the wheat heads. Research conducted under the United States Wheat and Barley Scab Initiative suggests that the fungicide should be applied with 10 to 20 gallons of water per acre and a low rate of non-ionic surfactant. Either a single tapered flat fan nozzle oriented forward at 30º from horizontal or a double orifice nozzle (twin jets or twin nozzles) in a forward/backward orientation can be used. They also found that the greatest disease suppression is attained with spray droplet sizes of 275 to 350 microns, which falls between the high end of the fine category to the low end of the medium category droplet size.

White wheat vs. red wheat

Consider local markets. Discount schedules for DON-contaminated wheat varies, not only with current market considerations, but also by wheat type. Soft white wheat is often discounted more than soft red wheat due to milling product requirements. For example, white wheat discounts for white wheat grain might begin when DON levels reach 1 ppm, whereas contaminated red wheat may not be discounted until DON reaches 3 ppm. Therefore, the risk of financial losses from DON is greater for white wheat than red wheat.

Regional reports

1 – Southeast

Ned Birkey

Weather

The weather has finally straightened out with nice spring conditions here. Farmers have been out of the fields for one full week. We had about 2.5 to 3 inches of rain, primarily last week, with scattered rains this week on Tuesday, May 1. Soil temperatures have increased and stayed around 53ºF for the past three days.

Crop reports

Alfalfa and grasses are growing nicely, with advanced fields about ten inches tall. Alfalfa weevil feeding has started, but is not at economic levels.

Corn planting resumed yesterday in select dry fields after a full week of rain and wet soil conditions. I have not seen any corn emerged, though it should with the favorable weather forecast for the next week.

Oats have loved the cool and wet weather.

Soybean planting may resume this week, though corn will take top priority and soybean acres will be down anyway.

Wheat is just at the Feekes’ growth stage 6, with some topdressing and weed control going on where field conditions allow. Most fields look good as poor fields have been destroyed and planted to corn.

Miscellaneous

Farmers are not behind the “eight ball” of corn planting, but now that May is here, planting takes on a new sense of urgency. The Red Wings must have sensed the same feeling of urgency in their come-from-behind win last night.

2 – Southwest

Bruce MacKellar

Weather

 The last weekend in April was beautiful, but soils remained wet in southwest Michigan. With rainfall totals ranging from 1.5 - 2 inches of precipitation during the previous week, soils were mainly too wet for much progress to be made in field work during the weekend. More rainfall that fell over the region Sunday night may have also slowed progress in limited areas. Most locations in the southern tier of counties missed the rain that fell in Michigan on Tuesday, May 1. With drier conditions on tap for the next several days, we anticipate that the planting will continue in earnest this weekend.

Crop reports

Commercial corn planting is progressing very slowly in the region. In St. Joe County, I would place the commercial corn planting progress at about 15-20 percent. In areas closer to Lake Michigan, the percentage planted is substantially less than this. We have found our first field of corn that had emerged in Kalamazoo County this week. Due to the heavy growth of winter annual species, such as chickweed and purple deadnettle, during the first part of the spring, and again now in fields where tillage has been delayed, it may be prudent to keep an eye out for cutworm damage in corn and soybean fields. If you have had challenges with sandhill cranes in your area, I would encourage you to read the article written by Chris DiFonzo in last weeks CAT Alert. The seed treatment Avitech has the potential to help alleviate the problem. At a cost of $5.50 - $6.00 per acre, it can be a good investment on fields planted near wetlands and wooded areas, where cranes have cause significant damage in the past.

Seed corn planting is about three to five days behind the norm this year due to cold soil temperatures and wet conditions this spring. The first seed corn production fields should begin to be planted this week. Due to high numbers of flea beetles found last fall and the relatively mild winter conditions, as well as snow cover during the late freeze, we may find flea beetles to be prevalent again this spring.

Soybean planting is just getting underway in southwest Michigan. With the delay in planting, soybeans will probably go in substantially later this year, as producers will focus on planting corn first at this point.

Alfalfa growth has been very slow following the freezing conditions in April. In areas where the fields had broken dormancy and there was little snow cover, the crop was significantly impacted by the freezes in April. Weeds have had an ample opportunity to grow as many fields were set back by the frosts. Alfalfa weevil have also been active, and the plants are still quite small at this time, so I would encourage producers to keep an eye on their fields and be prepared to spray to control the pests before they cause significant defoliation. Since we are a long ways from the first cutting in a lot of these fields, there is a good possibility that they will have to be treated this spring rather than waiting for the first cutting for control. You can use a sweep net to detect adults and larvae. Before first cutting, sample 20 stems in 5 different locations of the field; look for larvae and damage. After first cutting, check stubble or re-growth for larvae. Before first cutting, treat when 40 percent of stems damaged, plus live larvae present; after first cutting, treat when 25 percent or more of new tips damaged, or 6 to 8 larvae per square foot of re-growth.

We don’t have all that much wheat in my area of the southwest region, but the fields that I have looked at in St. Joseph, Van Buren and Kalamazoo counties look pretty good following a period of stress after the brutal spring freezes in April. Wheat is primarily in Feeke’s Stage 6, where the plants have the first joint visible. There is already some evidence of powdery mildew on the plants. It would be worthwhile for folks to keep an eye on their wheat fields as the season progresses to watch for the leaf disease movement towards the upper leaves of the plant. With warmer and drier conditions in the forecast, it should help slow down the progress of this leaf disease.

3 – West Central

Fred Springborn

Weather

Minimum soil temperatures as recorded at the MSU Experiment Farm in Entrican have risen to the mid 40s to lower 50s this week. Rain showers were light in the latter half of last week with a half inch falling over much of the area on April 26 and 27 allowing field work to resume as early as Saturday on a few well drained soils and by late Sunday on many of the sandy soils. The 1 inch  of rain that fell on late Monday and Tuesday halted work and has kept work from progressing until today on well drained soils.

Crop reports

Wheat is in Feeks growth stage 5 and approaching 6 in some fields. Winter annual weeds continue to grow well and many fields will need to have the herbicide applied soon.

Oat planting is progressing well with most of the crop planted. Early planted fields have emerged.

Sugar beet planting is progressing rapidly where soil conditions will allow. There is still a portion of the crop yet to be planted on the heavier more poorly drained soils.

Corn planting has continued as soil conditions allow 10 percent of the crop planted on well drained soils.

Soybean planting has begun on a very limited basis (less than 1 percent).

New growth on alfalfa is 6-8 inches. New seedings are being established.

4 – Central

Paul Gross

Weather

There were scattered rains over the region over the past week with heavier rain Monday evening and Tuesday (April 30-May 1). Many areas received over one inch making most fields too wet for field work. Field activities this week included limited planting, herbicide and fertilizer applications. It appears it will be the weekend before farmers will be able to get back into the fields.

Crop reports

There was limited corn planting over the past week. Across the region there is about ten percent of the crop planted. Planting will resume as fields dry out. It will be very important to wait that extra day or two to allow fields to dry out. Research shows yield reductions when planting in wet soils.

The wheat crop is in Feeke’s 4-5. Weed control and nitrogen applications are being made as conditions allow. It is important to know the growth stage of your fields to choose the correct herbicide. If your fields are past Feeke’s 5, you should not use 2,4-D because of the risk of yield loss. We are seeing in some fields that the excessive moisture is hurting the stand. We have observed some nutrient deficiencies in some areas of fields.

Alfalfa growth is very good at this time. Fields are 8-10 inches tall. There has been no observed alfalfa weevil feeding at this time. Fields should be scouted for this pest.

Oats and alfalfa seedings are nearly complete with emergence expected soon on early planted fields.

5 – Thumb

Mark Seamon

Weather

Most of the Thumb area received about a half inch of rain this week. This rain added good soil moisture, but stopped planting progress. Air temperatures are cool, which are slowing the drying. This is good to reduce soil crusting, but it also is delaying planting.

Crop reports

Alfalfa’s new growth looks good.

Very early planted sugar beets (end of March) have emerged pretty well. Not perfect stands, but the timing of the crop is good. Thin soil crusting has reduced some stands. Planting is about 75 percent complete at this point. Mid to late April planted fields are emerging nicely with good moisture conditions.

The wheat crop looks good in most areas. Some growers are still evaluating fields to determine yield potential and to decide if the crops should be kept or converted to another crop. A few fields look great, but most are average.

Corn planting is nicely started but less than 25 percent is planted throughout the Thumb. Planting conditions were mostly good, but time was limited. PPI and pre-plant herbicides should work well with adequate rainfall after application. This crop will be planted in very short order when the opportunity arises.

A couple of fields of soybeans have been planted, but it has been very limited up to this point.

Weather news

Jeff Andresen
Agricultural Meteorology
Geography

Upper air ridging and high pressure were entrenched across the Great Lakes region Thursday, May 3 and will bring a day of mostly sunny skies and seasonable temperatures to Michigan. Remnants of a trough of low pressure currently over the southern Great Plains will drift towards the state by late Friday into Saturday, bringing a temporary increase in cloudiness and a small chance for some light showers across far southern sections of the state. Otherwise, fair and dry weather is expected to continue. Look for daytime temperatures from the mid 60's to low 70's Thursday through Saturday, warming to the mid or upper 70's by Sunday and Monday. Low temperatures will range from the 30's to the low 40's Thursday and Friday mornings, warming to the 40's to low 50's by Sunday. Given a very dry air mass in place across the region, some scattered frost is possible on Friday and Saturday mornings mainly in sheltered, low-lying areas in northern sections of the state should clear, calm conditions materialize. Most areas should remain well above freezing.

 Medium range forecast guidance is currently in good agreement suggesting upper air troughing across the western United States and ridging over the east, with southwesterly flow across the Midwest and Great Lakes regions. The official NOAA 6‑10 day and 8‑14 day outlooks (covering May 8-12 and 10-16, respectively) both call for above normal temperatures state‑ and region-wide. Total precipitation during both time frames is forecast to range from near normal levels across extreme southeastern sections of the state to above normal levels elsewhere. Extended outlooks for central and western sections of the Corn Belt region (where planting has been delayed recently due to heavy rain) are very similar, with warmer and wetter than normal weather expected.

Further ahead, the new NOAA Climate Prediction Center 30-day outlook for May is consistent with the medium-range forecasts, calling for warmer than normal temperatures statewide. The precipitation outlook is more uncertain, with Michigan expected to remain between forecast areas of above normal precipitation totals to our west and below normal precipitation totals to our east.