Vol. 20, No. 5, May 12, 2005

In this Issue
Soybean rust movement update: Florida and Georgia
Soybean aphid reproduction on buckthorn
New web site available for soybean growers
Fusarium head blight of wheat (wheat scab)
Alfalfa weevil scouting
Soil pests and seed treatments
Dandelion management in field and forage crops
Delayed herbicide application in corn
Variable sugar beet emergence and weed control
PSNT refresher
Regional reports
Weather news

Patrick Hart
Plant Pathology

Soybean rust (SBR) has only been found on kudzu in four counties in Florida and on volunteer soybeans in one county in Georgia. Growers should be developing an action plan for the possibility that rust will move into Michigan this summer. However, no specific actions are recommended at this time. Refer to the April 21 issue of the Field Crops CAT Alert for more information.

 As a reminder, 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/

Christina DiFonzo, Entomology

Soybean aphids are reproducing on buckthorn, but I have not seen winged individual yet. I had the same report from Ontario yesterday. Early-planted beans are reported just coming up, so when winged aphids appear, they may find a host.

Rebecca Lamb, Asst. Editor

Since the onslaught of new soybean pests has occurred in Michigan, the Integrated Pest Management Program has worked to make the best information available in one place for growers. The new pages on soybean rust and soybean aphid have all previous articles from the Field Crop CAT Alert in one place for easy reference. The pages can be found at:
http://www.ipm.msu.edu/soybean/rust.htm and http://www.ipm.msu.edu/soybean/aphid.htm

To stay up-to-date on information about these new pests, please check these pages for new information.

Patrick Hart
Plant Pathology

It's that time of the year again to start thinking about wheat scab. Although the Penn State Model FHB prediction model did not work well for Michigan last year (overall it was about 65% accurate across the United States), the researchers feel they have made some improvements to data collection and presentation that should improve the predictive capability of the model. It’s important to remember that the model is only good as a prediction for the development of fungal spores prior to flowering. Conditions could be favorable for spore development and release, but then change and not be favorable for infection. But that is a chance we have to take.

Michigan is still waiting to hear from the EPA on the approval for the Section 18 for Folicur, although it was approved for use in Kentucky. Hopefully, we should have some information soon. In the absence of Folicur, the next best fungicide is Tilt. It is important to remember that the best scab control will occur when the fungicides are applied as close to the beginning of flowering as possible. The later into flowering Tilt or Folicur is applied scab control will be less effective. Both labels allow application up to flowering (Feekes 10.51), but also say that they cannot be applied within 30 days of harvest. I would not recommend putting either fungicide on after flowering has been observed in fields for seven days. This would still be GS 10.51 or the beginning or flowering. It’s important to look for flowering throughout the field because flowering usually starts at the margins before it begins in the middle of the field.

Last year we got some great benefit for Septoria leaf and glume blotch, but we should only be applying Tilt (not Folicur) as a preventative for these diseases if there is at least 1% infection of the flag leaf at GS 10.51. Recommendations for the management of foliar diseases of wheat can be found as a pdf at: http://www.cips.msu.edu/people/hartp/nWHEAT.pdf

The web site for the Penn State Scab Model is www.wheatscab.psu.edu.

I hope that we can have our own scab prediction site up within the next week, so we can compare both sites. Our site uses a model developed by Penn State, but uses slightly different environmental parameters to determine if the conditions are favorable for spore development and release. This model seemed to work well for Michigan last year, but this might be related more to the source of the weather data rather than actual differences between the models. I would expect flowering to begin sometime in the next two weeks starting in the southern counties, although we seem to be a little behind last years growth.

Remember, the researchers at Penn State are saying the model is a work in development, so the results cannot be guaranteed.

Christina DiFonzo, Entomology

Limited reports of alfalfa weevil feeding are coming in from southern Michigan, but as the weather warms back up, expect an increase in activity. The easiest scouting method uses “tip injury. ” Survey across the field – not just on one side or on an edge. Check tips of 100 stems for feeding. Treat if 40 percent of stems show damage and the field won’t be cut for at least seven days.

Another scouting method is the “stem and bucket” action threshold from Ohio State University, which uses both weevil number and crop height. Collect 30 stems at random (snap off at base) into a bucket from a field. Shake the stems into the bucket to knock off late instar larvae (i.e. the big guys). Don’t worry about the little larvae. Count the total number of larvae in the bucket, then randomly select 10 of the 30 stems you just picked and measure the average stem height (I marked a ruler on the handle of my sweep net.). The treatment threshold, in number of larvae per 30 stems, varies with average stem height in inches, as follows: 12 inch – 30 to 50 larvae; 16 inch – 40 to 75 larvae; 20 inch – 45 to 85 larvae; and 24 inch – 50 to 90 larvae.

If a field is over threshold but will be cut within the next week, consider cutting early to kill weevils. This is the preferred control method because it preserves natural enemies and pollinators, and saves the cost of application. Also, most insecticides cannot be used within 7 to 21 days of cutting, depending on the product.

There are times, for example if forage quality might be adversely affected by cutting too early, when cutting is not possible. When a decision is made to spray, remember to note the preharvest intervals (PHI) of insecticides labeled for alfalfa. The PHIs range from 0 to 28 days, depending on the product and rate per acre. Also remember that there are many beneficial insects in alfalfa that are killed by sprays with longer residuals. Most labels include honeybee warning statements. Every year, the Michigan Department of Agriculture receives complaints about bee kills. It is a good policy to notify beekeepers in the neighborhood when you do spray, because they may be able to move hives or restrict bee movement for a few hours. Fields in bloom should never be sprayed because all of the insecticides registered for alfalfa are toxic to bees – these fields should be cut.

After cutting, remember to check for weevil larvae on the regrowth, which can delay or prevent green-up. The threshold after cutting is six to eight larvae per square foot of regrowth.

Christina DiFonzo, Entomology

I have had several questions about soil insect feeding and seed treatments over the past week. Many fields in Michigan were planted in early to mid-April – this means some seed has been sitting in the ground for nearly a month and is just germinating.

The longer that seed sits in the ground and the longer that it takes seedlings to grow, the greater the potential for damage from a whole host of soil insects. Slugs, seedcorn maggot, wireworm and grubs are the most common culprits in reducing emergence in Michigan. It has been fairly dry across the state, and slugs do not appear to be a problem. Seed corn maggots and wireworms often attack the seed before or at germination, so the plants never emerge. Grubs prune the roots, weakening or killing small plants. Grubs may be responsible for some of the spotty wheat stands in the Thumb. To determine if, or which, insect is responsible for poor emergence or weak plants, you have to try to find insects in the soil.

If your seed was treated with Poncho or Cruiser, it is a good idea to have a copy of the actual label for the insecticide. Growers have told me that they do not receive this label with treated seed, but the labels can be found on the Internet. Get them and read them! There is important information about seed disposal and plant back restrictions (important given the replanting occurring after the recent frost).

Here are some interesting tid-bits from the Poncho labels.

§      Plant back restrictions: Corn, canola, rape-seed = immediate replant; Cereal grain, grasses, non-grass animal feeds, SOYBEAN, DRY BEANS = 30 DAYS; All other crops: one year!
§      Wear gloves when handling seed (after all, it is insecticide-treated!).
§      Do not dispose of treated seed on the soil surface (animals may eat it).

Here are some interesting tid-bits from the Cruiser 5FS label:

§      Plant back restrictions: barley, corn, canola, cucurbits, fruiting and legume vegetables, mint, oil seed crops, root vegetables, sorghum, strawberry, sunflower, tuberous vegetables, and wheat = immediate replant. For any other crop = 120 days.
§      Same warnings about wearing gloves, and disposal on the soil surface.

Jim Kells, Kathrin Schirmacher and Christy Sprague
Crop and Soil Sciences

Dandelion continues to be a serious problem in Michigan. We have received numerous calls about dandelion in emerged no-tillage corn and soybean. Dandelion is a problem mainly in no-tillage fields. Regular soil disturbance prevents the establishment of dandelion plants.

Research conducted at Michigan State University in 2001 through 2003 studied the control of dandelion in no-till corn and soybean. The results showed that herbicide applications of either glyphosate (0.75 lb a.e/A. + 17 lb/gal AMS) or 2,4-D ester (1 lb a.e./A) are more effective in the fall than in the spring. Additionally, 2,4-D ester was less effective than glyphosate in both fall or spring applications. Details on the results of this research are in the fact sheet, which also appears in the 2005 weed Control Guide for Field Crops, pages 150-151.

The best approach to dandelion control is prior to planting a crop. However it is not uncommon for herbicides to provide less than complete control, especially if applied in the spring. What are options for dealing with uncontrolled dandelion following crop emergence? Where corn or soybeans have emerged and established dandelion are present, the strategy should be to suppress the plants to minimize yield loss from dandelion competition. In-season applications will significantly reduce dandelion competition but will likely not greatly reduce dandelion population. Then a fall application can be planned following harvest with the goal of actually removing the plants.

Corn. Several postemergence provide significant dandelion suppression. These are listed in the fact sheet, which also appears in the 2005 Weed Control Guide for Field Crops, pages 150-151.

Soybean. Glyphosate is the best option for postemergence suppression of established dandelion.

In established alfalfa, dandelion can be controlled with Velpar. The treatment can be made in the fall or spring, however the most effective timing for dandelion control is in the spring before the alfalfa has two inches of new growth. The bets timing for maximum crop safety is early spring before the alfalfa breaks dormancy. The application rate for dandelion control is 1 lb ai/A. Velpar is not widely used for dandelion control due to cost and rotation crop restrictions.

Jim Kells and Kathrin Schirmacher
Crop & Soil Sciences

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

In fields with emerged corn and no herbicide applied, growers have two primary options: 1) use an herbicide program typically applied before emergence; or 2) switch to a total postemergence strategy. There are several possible herbicide programs with each strategy.

Table 1K in the 2005 Weed Control Guide for Field Crops lists herbicides typically applied preemergence. Many of these herbicides are also labelled for application after corn emergence. Axiom and Princep should only be applied before corn emergence. To avoid confusion, tank mix combinations are not included in the table. Details on the specific restrictions for tank mixtures can be found on the herbicide labels. Although some herbicide labels allow application to emerged corn using 28 percent liquid nitrogen fertilizer as the herbicide carrier, we advise that all herbicide treatments to emerged corn be applied with water as the carrier. Applying herbicides to emerged corn with 28 percent liquid nitrogen as the carrier poses a risk of severe crop injury. This risk is increased under cool, cloudy conditions prior to application, a common occurrence in Michigan.

Preemergence herbicides should be applied as soon after planting as possible. Delayed application increases the risk of poor herbicide performance, especially for grass control. When herbicide application is delayed until after crop emergence, rotary hoeing is recommended. The rotary hoeing may be done before or after the herbicide application, but must be done when the weeds are very small. If the delayed application includes Banvel/Clarity, Distinct, Marksman (or other herbicides containing dicamba) or Prowl/Prowl H₂O/Pendimax, corn safety will be greater if the rotary hoeing is done before herbicide application.

Herbicide options for total postemergence weed control are dependent on the seed planted in the field. Many postemergence herbicides can be used on any corn hybrid, while others such as Liberty, Lightning and glyphosate require herbicide resistant hybrids. For details on postemergence herbicides for corn, see Extension Bulletin E-434.

Christy Sprague
Crop & Soil Sciences

Swings in temperatures and dry conditions after planting have left many fields with sugar beets that range from emergence to early 4-leaf beets. Depending on your plans for weed control this season, variable sugar beet size may be an issue. If your weed control strategy includes a lay-by application of Dual Magnum or Outlook, or if you are planning on increasing the rate of either Betamix or Progress in your micro-rate or standard-split herbicide application you need to keep in mind that sugar beet size can be a contributing factor to injury from herbicides. Sugar beets are much more tolerant to herbicides as they get larger in size. In most cases, sugar beets are less sensitive to stand loss from herbicide applications once they reach 2-true leaves and are less sensitive to injury if sugar beets have 4- to 6- true leaves.

For example, last year in our research trials when we added Dual Magnum and Outlook to various micro-rate applications (first, second, third, and fourth timing) the greatest sugar beet injury occurred from the addition of these herbicides to the first micro-rate application timing (cotyledon beets). Keep in mind this application timing is not labeled for either herbicide. Sugar beet injury was 10 to 15 percent less when either herbicide was added to the second micro-rate (2-leaf beets), and injury was significantly lower when these herbicides were added to the third (~4-leaf beets) or fourth (~6-leaf beets) micro-rate timings. The same could be true with higher rates of Betamix or Progress in micro-rate or standard-split herbicide applications when beets are small.

In the April 7 issue of the Field Crops CAT Alert under the article New Herbicide Labels and Label Changes in Sugar beets, I wrote about changes that were made to the Betamix and Progress labels in regards to the rate structures for micro-rate herbicide applications. Again it is important to consider sugar beet size when deciding on the appropriate rate for you weed control situation. Remember if micro-rates are appropriately timed increasing the rate of Betamix or Progress typically will not improve weed control, furthermore crop tolerance may be more of an issue, particularly with the smaller sugar beets in the field. So when making decisions on when to apply a lay-by application of Dual Magnum or Outlook or whether you should increase the rate of Betamix or Progress, remember that your decisions should be based on the smallest beets in your field.

Darryl Warncke
Crop & Soil Sciences

The Presidedress Soil Nitrate Test (PSNT) is based on two principles:

1)    Organic forms of nitrogen in the soil are converted by microbial activity to the nitrate form, which is readily available for uptake by crop roots; and

2)    Nitrate that becomes available is nitrogen that does not need to be supplied by purchased nitrogen.

The rate of decomposition of organic forms of nitrogen, whether soil organic matter, crop residues, animal manure or compost, increases with increases in soil temperature. By the time it is time to sidedress corn with nitrogen, a significant amount of the organic nitrogen will have been converted to nitrate.

Although nitrate will continue to be release from the organic materials throughout the growing season, the amount of nitrate present in the soil at sidedress can be used as a credit against the total amount of nitrogen required for the corn crop.

The MSU recommendations for corn grain and corn silage are based on the following formula: Corn grain N rec. (lb N/A) = (1.36 x yield in bu/A) – 27 minus any N credits

Corn silage N rec. (lb N/A) = (8.33 x yield in tons/A) -25 – minus any N credits

N credits may come from legumes, manures, compost or soil organic matter. The PSNT provides documentation of the available nitrogen status of the soil at the time the soil sample is taken. And this amount of nitrogen can be used as a credit and guide for how much additional nitrogen, if any, will be needed to meet the need of the crop. Soil samples for the PSNT should be taken from the 0 to 12 inch depth. It is best if one sample, a composite of 15 to 20 cores, represents not more than 20 acres. A test value of 25 ppm, (about 150 lb N/acre) on a soils basis at sidedressing time indicates that there is sufficient nitrogen available in the soil for maximum yield. The PSNT is a good diagnostic tool for economic nitrogen management. PSNTs are provided by all soil testing labs with quick turn-around time.

Regional reports

1 – Southeast

Ned Birkey

Weather
It has been very nice, warm and dry until yesterday (May 11) when scattered and locally heavy showers stalled some fieldwork. The weather is iffy for the rest of the week. Farmers are thankful for today’s showers, even if scattered. Soil conditions have been nice, but getting very dry.

Commodity reports
Alfalfa is growing nicely, as are the grasses, some of which are heading out. Fields are about 15 inches tall and will make a nice first cutting very soon.

Corn planting is about finished, which is really nice and timely for a change. This past Monday emerged corn could be rowed.

Soybean planting continues and is about two-thirds finished. No soybeans have emerged that I am aware of, though there could be some emerged with the nice weather earlier this week.

Wheat is in Feekes’ stage six and most fields look very good with nice uniform stands and growth. The rain yesterday has helped.

Commodity prices are discouraging, along with higher fuel, seed and fertilizer prices. At least this May has been good for planting compared to the previous three years. To have this much progress by May 12 is great.

Bruce MacKellar

Weather
Thunderstorms occurring over the region on the morning of May 11 brought some much-needed rainfall.  This is sure to help crops planted in very dry soils to begin to germinate.  Many locations in southwest Michigan were running 3 to 3.5 inches behind normal precipitation levels since April 1.  Rainfall amounts ranged from just under an inch to around a quarter of an inch.

Commodity reports
Planting progress is nearing completion for commercial corn.  All but the very earliest planted fields appear to have avoided frost/freeze injury because it remained underground during the worst of the cold weather.  Corn that emerged before April 20 was severely affected by frost, especially the May 4-5 events.  Some of these fields are being replanted now. Others will likely be re-planted.  Stands look good in fields currently emerging.  Herbicides had been applied for several weeks before there was enough rainfall to activate the chemical.  It is too early to see if this will adversely affect weed control in these fields.  Despite of the length of time in the soil, there has been very little incidence of seedling rots in fields that I have walked in so far.  Soil insect activity also appears light at this point.

Planting of seed corn has been progressing very quickly over the past week.  Many fields have either the male or the female inbred planted and are waiting for the proper heat unit accumulation to occur to plant the other parent line. 

Planting is progressing rapidly in soybeans.  Most of the earliest planted beans are breaking ground or are in the cotyledon stage.  Seedling emergence looks very good despite the fact that many fields have been planted three weeks or more before they began to emerge. 

Snap bean planting is scheduled to begin this next week.

The dry weather allowed the potato producers to get an early start and continue to plant almost non-stop over the last month.  Emergence has been a little slower than anticipated, most likely due to the cold weather but seems to be on track at this point in time.

Alfalfa is growing quite well right now despite the dry conditions.  Heights range from 12-15 inches.  Van Buren County MSUE Educator Mike Staton reports that he is beginning to see significant alfalfa weevil larvae feeding in at this time.  I have seen less of this to the east, but it is definitely time to scout your fields to determine if the pest is present.  Please refer to Dr. DiFonzo’s article in this issue of the Field Crop CAT Alert for more information on controlling this pest.  Top quality first cutting alfalfa should be harvested at 750 GDD41.  The southwest region has wide variations in GDD41 this season.  The following values represent heat accumulations for some areas across the region:  Battle Creek – 469, Kalamazoo – 562, South Bend – 501, Coldwater – 374.  To monitor the GDD41 heat accumulation in the coming weeks, you can go to the following website:  http://www.agweather.geo.msu.edu/Ldm-Data/bs41.dat

Mike Staton reports that wheat is approaching Feeke’s Stage 9 with flag leaves emerging in some areas.  Wheat stands look good for the most part this season with the dry conditions limiting the incidence of leaf diseases such as powdery mildew.  Dry conditions did affect lower leaves on some fields in St. Joseph County.

For more information on pest conditions in southwest Michigan, you can visit the St. Joseph County IPM Breakfast website at: http://web1.msue.msu.edu/stjoseph/anr/IPM/2005/051105.htm

Fred Springborn

Weather
Warmer temperatures have prevailed for much of this past week. High temperatures have been in the mid-60s to low 80s with lows in the lower 40s to mid-50s. Soil temperatures have improved with the highs in the 60s to lower 70s and the lows in the upper 40s and mid-50s. Two-tenths of an inch of rain fell over much of Montcalm. Other wise it has been generally dry, many areas of the region could benefit from a more substantial rain shower.

Commodity reports
Oats have emerged and stands look generally good. Wheat is at Feekes stage 6 and few disease problems have been noted.

Rye is at Feekes stage 8.

Corn is 90 to 95 percent planted and very little has emerged.

Sugar beets have emerged. Stands are good.

Soybean planting is 65 percent complete.

Alfalfa is 9 to 12 inches in height with few problems observed.

Paul Gross

Weather
The region received one- to two- tenths of rain yesterday. The light rains kept farmers out of the fields for most of the day. Planting will resume today in most cases. Planting has progressed nicely with generally favorable soil conditions. The warmer weather this past week has been just what is needed for wheat, alfalfa and emerging crops.

Commodity reports

The corn crop is about 90 percent planted. There is some emergence in the southern part of the region and none in the north. Most early-planted corn should emerge in the next few days or as temperatures improve. Pre-emergence herbicide applications are being applied.

Soybeans are about 70 percent planted. There have been reports of the early-planted fields just beginning to emerge. One more week of good weather will be all that is needed to finish planting soybeans.

The wheat crop is in Feeke’s 6-7. The stands seem to be either very good or very poor. In Isabella County about 10 percent of the wheat crop will be abandon because of poor stands. They are the result of winterkill and late planting. There have been a lot of nitrogen and herbicide applications being made over the past week to ten days. Warm temperatures are needed. Some powdery mildew is present in some fields. Fields should be scouted for foliar disease.

The oats and barley crops look very good at this time with excellent stands. The cool weather has been ideal for these crops.

Alfalfa is 10 to 12 inches tall and growing slowly. There are no reported insect problems at this time. Fields should be scouted for alfalfa weevil. Most stands have some evidence of winterkill. The new seedings are doing very well.

Sugar beets are emerging slowly with stand generally OK.

Mark Seamon

Commodity reports
New alfalfa growth continues to look good.

In sugar beets, some stand loss from frost occurred in a few fields. Weed control with micro rate herbicides is on schedule. Weed growth is active. The recent rain should help some late emerging beets to break through the surface.

The wheat crop has made good use of the recent high temperatures and sunshine to move through development. Weed control applications have been active in the past week. The use of growth regulator herbicides should be avoided at this time due to growth stage.

The past week has nearly completed the planting of corn. I have heard reports of a few emerged early-planted fields. Most other fields are developing nicely with emergence likely in the next five days.

Soybean planting has been in full swing this past week with 70 to 80 percent of this crop planted. A few fields have emerged but most have not. Some soybeans have been planted for up to four weeks and are waiting for increased soil temperatures to emerge.

Jeff Andresen
Agricultural Meteorology
Geography

Despite widespread snow and rain during the last week of April, precipitation totals across Michigan have consistently remained below normal since early March. The extended dryness has resulted in depleted topsoil moisture levels in many areas of the state, especially given recent warm temperatures and accelerated potential evapotranspiration rates. Some rainfall is in the forecast during the next few days, although amounts and areal coverage remain somewhat uncertain due to inconsistencies in numerical forecast guidance. High pressure is expected to dominate the region Thursday with fair and dry weather expected statewide.

Friday and Saturday (May 13-14), another weather disturbance will approach from the southwest, bringing a good chance for showers and thunderstorms to nearly all of the state. Drier weather is expected by Sunday. Temperatures will vary widely across the state during the next few days. High temperatures will remain in the 50s in northern sections of the state with some upper 40s possible in northern lakeshore areas. Highs will be in the 60s in the far south. Some nighttime freezing temperatures will be possible in interior sections of the Upper Peninsula Friday morning with above freezing temperatures (upper 30s to mid 40s) elsewhere. In the medium range time frame, latest forecast guidance calls for a general westward shift of the major upper air features of the past week, which would put Michigan under the influence of northwesterly flow. The NOAA Climate Prediction Center 6-10 day and 8-14 day outlooks both call for near normal temperatures and below normal precipitation totals state- and region-wide.

For the 3-month May through July period, the outlook suggests wetter than normal conditions across western sections of Michigan with the climatology scenario in the east. Temperatures statewide are officially forecast to remain in the equal odds category, although cooler than normal temperatures are expected just west of the state across areas of the Upper Mississippi Valley.