May 31, 2007
In this issue
§ Insect update
§ Timely postemergence herbicide applications in corn
§ Optimize N inputs: Use PSNT
§ Nitrogen fertilizer management strategies
§ Wheat disease update
§ Regional reports
§ Weather
Christina DiFonzo, Entomology
There have been several
reports of bean leaf beetle feeding on soybeans. This is not a surprise, since
the mild winter likely increased beetle survival. The beetles feed in alfalfa
early in the season, then move to early-planted (first emerging) soybean fields
after first-cutting. The adults cause damage by defoliating young plants,
leaving small round holes between the leaf veins. Young soybeans can tolerate
and recover from considerable injury (25 to 30 percent defoliation) without
loss of yield. Although feeding injury may be common, it is rare to have entire
fields in
Although I haven’t
personally confirmed soybean aphid in
David Hillger
Crop & Soil Sciences
For several years, MSU has demonstrated the importance of timely herbicide applications to prevent the loss of yield in corn. We have shown that it is necessary to control weeds before they reach 4 inches of growth to prevent measurable yield reduction. Two-pass herbicide applications (preemergence followed by postemergence or two postemergence) or timely single postemergence applications with residual control, are most effective at preserving yield and maximizing gross margin. Information about the effectiveness and economics of preemergence and post emergence herbicide programs can be found in the three-year summary of Commercial Herbicide Program Comparisons found on the MSU Weed Science website at http://www.msuweeds.com/publications/.
Herbicide options for total postemergence weed control are dependent on the hybrid planted in the field, and the size of the corn at the time of application. Several herbicides have height limitations of 12 inches or less, such as atrazine and dicamba, while other herbicides may be applied to taller corn. Identifying the height and growth stage of the crop is important to prevent possible crop injury. Specific height restrictions for postemergence herbicides can be found on their label or in the 2007 Weed Control Guide for Field Crops Extension Bulletin E-434, in table 1J on page 52.
Timely weed control is important in minimizing yield loss due to weed competition and crop injury due to off-label herbicide applications. During ideal growing conditions, this window of opportunity may be very small, so it is important to monitor the progress of your crop and scout for weed problems before they cause lasting damage.
Darryl Warncke
Crop & Soil Sciences
Each crop year has its unique weather features. Knowing the weather would really help in preparing a nitrogen management plan. The greater the time between nitrogen application and the time of greatest nitrogen need by a crop, the greater the risk of nitrogen loss from the rooting zone of the soil. At the V-6 stage of growth (about 25 days after emergence), a corn crop has only accumulated about 5 percent of the total amount it will use. At the V-8 stage, corn is entering a rapid growth phase where nitrogen uptake increases rapidly. By the V-12 stage (approximately 45 days after emergence), the crop has accumulated about 30 percent of its nitrogen need.
During the first five week period after planting corn, significant amounts of nitrogen may be mineralized (released) from the soil organic matter, incorporated crop residues or manure. Nitrogen released in the soil is nitrogen that does not need to be applied as fertilizer. The question is how much will be released. Collecting soil samples near the V-6 stage of growth and having the soil analyzed for the available nitrogen status, gives a good indication of how much the soil is able to supply and how much additional nitrogen is needed. Field studies, over the past several years, have shown the PSNT (presidedress soil nitrogen test) to be a reliable indicator of additional nitrogen need and have provided the most economical use of nitrogen resources.
Soil samples for the PSNT should be taken from the zero 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. Most all soil testing labs, including the MSU Soil and Plant Nutrient Lab, provide PSNT testing with quick turn-around time (within 48 hours of receiving the sample). The fee for this test ranges from nine to 12 dollars.
Editor’s note: This article was first printed in the April 20, 2006 edition of the Field CAT Alert.
Nitrogen fertilizers are expensive and may become unavailable to your crop. Because of this, corn producers will need to manage nitrogen fertilizer carefully to remain profitable in 2007. Here are some strategies for getting the most from your investment in nitrogen fertilizer.
Studies have shown that only 40 to 60 percent of the nitrogen you apply is taken up by your crop. Another 20 to 30 percent remains in the soil after harvest and 10 to 20 percent becomes unavailable to plants during the growing season. The losses are due to three processes, volatilization, leaching and denitrification. Volatilization occurs when fertilizers containing urea undergo rapid hydrolysis in the soil. Significant losses of ammonia gas can occur. Nitrate-nitrogen is susceptible to losses from leaching and denitrification. Leaching is most likely to take place in coarse-textured soils. Denitrification of nitrate-nitrogen occurs under saturated conditions on fine-textured soils. Over 100 lbs. of nitrogen per acre can be lost from denitrification in five days under the proper conditions.
The three main nitrogen fertilizer sources are anhydrous ammonia, urea and urea ammonium nitrate solutions (UAN). Anhydrous ammonia is still the least expensive form of nitrogen. It must be injected 6 to 8 inches deep and the slot must be sealed to prevent losses. If applied properly, it is the most stable nitrogen source as it is the slowest fertilizer to be converted to nitrate. Urea is subject to volatilization losses. Volatilization occurs rapidly under warm air temperatures in fields having low CEC’s, heavy residues and adequate moisture. These losses can be reduced by incorporating the fertilizer with tillage at least 1 to 3/4 inches deep or by at least 3/4 of an inch of irrigation or rain fall. Urease inhibitors are available to mix with the fertilizer and prevent volatilization for 10 to 14 days following a surface application. The urea will not be available to plants during this time. UAN solutions are comprised of half urea and half ammonium nitrate. Therefore, half of the nitrogen is subject to volatilization losses. About 25 percent of the nitrogen is in the nitrate form at the time of application and is subject to losses from leaching or denitrification.
The first step is to determine your price per pound of actual nitrogen and the market price you expect to receive for your corn. Determine the corn to nitrogen price ratio from Table 1. Next you will need to set realistic yield goals for your fields. A realistic yield goal is the average yield you attained in the field for the last five production years for that crop. Find the point on Table 2 where your yield goal and your corn to nitrogen price ratio intersect. You may have to interpolate between rows and columns. This is the most economical nitrogen rate for this field.
|
N cost ($/lb) |
Corn Price ($/bu) |
||||||
|
1.00 |
1.50 |
2.00 |
2.50 |
3.00 |
3.50 |
4.00 |
|
|
|
---corn:N price ratio--- |
||||||
|
.10 |
10:1 |
15:1 |
20:1 |
25:1 |
30:1 |
35:1 |
40:1 |
|
.15 |
7:1 |
10:1 |
13:1 |
17:1 |
20:1 |
23:1 |
27:1 |
|
.20 |
5:1 |
8:1 |
10:1 |
12:1 |
15:1 |
18:1 |
20:1 |
|
.25 |
4:1 |
6:1 |
8:1 |
10:1 |
12:1 |
14:1 |
16:1 |
|
.30 |
3:1 |
5:1 |
7:1 |
8:1 |
10:1 |
12:1 |
13:1 |
|
.35 |
3:1 |
4:1 |
6:1 |
7:1 |
9:1 |
10:1 |
11:1 |
|
.40 |
2:1 |
4:1 |
5:1 |
6:1 |
8:1 |
8:1 |
10:1 |
|
.45 |
2:1 |
3:1 |
4:1 |
5:1 |
7:1 |
8:1 |
9:1 |
|
.50 |
2:1 |
3:1 |
4:1 |
5:1 |
6:1 |
7:1 |
8:1 |
|
Source: MSU Extension Bulletin E-802 |
|||||||
|
Corn:N Price ratio |
Yield potential of soil (bu/A) |
||||||||||||||
|
85 |
100 |
115 |
130 |
145 |
160 |
175 |
190 |
||||||||
|
|
- - -most profitable N rate (lb N/A)- - - |
||||||||||||||
|
4:1 |
70 |
80 |
100 |
110 |
120 |
130 |
140 |
150 |
|||||||
|
5:1 |
80 |
90 |
100 |
110 |
130 |
140 |
150 |
170 |
|||||||
|
7.5:1 |
85 |
100 |
115 |
125 |
145 |
160 |
170 |
190 |
|||||||
|
10:1 |
90 |
110 |
130 |
140 |
160 |
180 |
190 |
210 |
|||||||
|
15:1 |
100 |
120 |
140 |
160 |
180 |
200 |
220 |
240 |
|||||||
Corn growers can reduce their nitrogen fertilizer application rates by taking credit for the nitrogen contributions from legumes, manure applications and the soil. The credits should be subtracted from the most economical nitrogen rate determined above. Soybeans will contribute 30 pounds of actual nitrogen to the following corn crop. Established alfalfa and clovers will contribute between 40 and 90 pounds of actual nitrogen, depending on the plant population. Manure can be an excellent source of nitrogen. The pre-sidedress nitrate test is a proven method for determining the nitrogen contributions from manured and non-manured fields. Do not take nitrogen credits when growing wheat. Wheat’s peak demand for nitrogen occurs earlier in the growing season before organic nitrogen has been converted to plant available forms.
|
PSNT Credit(lbs./acre) |
Cost Savings on Nitrogen ($/acre) |
Economic Gain($/acre) |
|
30 |
8.70 |
5.70 |
|
60 |
17.40 |
14.40 |
|
90 |
26.10 |
23.10 |
|
120 |
34.80 |
31.80 |
|
Source: Dr. Carrie Laboski Sampling and analysis costs are $3/acre |
||
Always apply at least 20 pounds of actual nitrogen per acre in a 2 x 2 band at planting time. Increase this amount to 30 to 40 pounds per acre when planting into heavy residues. Ideally, the rest of your nitrogen should be applied in early June as this coincides with the beginning of the crop’s peak demand for nitrogen. By applying most of your nitrogen in June, you will significantly reduce the potential for nitrogen losses due to leaching and denitrification. If you must apply your nitrogen prior to planting, consider using a nitrification inhibitor. These products can delay the conversion of ammonium to nitrate by four to 10 weeks. Nitrification inhibitors will work best if the nitrogen fertilizer rate is slightly deficient. Please see Table 4 to determine the probability of realizing an economic return from nitrification inhibitors.
|
- - -Time of Nitrogen Application- - - |
|||
|
Soil Management Group |
Early Spring <50 F |
Late Spring >50 F |
Side Dress |
|
Clays (0, 1) |
Good-Fair |
Poor-Fair |
Poor |
|
Clay loams (1.5) |
Fair-Good |
Poor-Fair |
Poor |
|
Loams (2.5) |
Fair |
Fair |
Poor |
|
|
Fair |
Fair |
Poor |
|
Loamy Sand (4) |
Fair |
Fair |
Poor |
|
Sands (5) |
Fair-Poor |
Fair |
Poor |
|
Key: Good=Economic response expected at least 60% of the time. Fair=Economic response expected 40-50% of the time. Poor=Economic response expected less than 30% of the time. Source: Nutrient Management to Protect Water Quality Bulletin WQ-25, 01/1996. |
|||
Diane Brown-Rytlewski
Plant Pathology
Powdery
mildew
Powdery mildew is the only wheat foliar disease showing up
with any regularity this season, and the amounts of it are quite variable. On
susceptible or highly susceptible varieties, there is a substantial amount of
mildew. With rain and humid weather along with cooler temperatures forecast for
the next few days, conditions may be favorable for powdery mildew to come up
out of the lower canopy where the temperatures have been cooler and more humid
and climb up on the flag leaves and heads. Fungicides registered for powdery
mildew control in
Fusarium
head blight
Wheat in
You can access specific information for a weather station
location at the
Click on one of the station locations. You will see an indicator bar showing
low (green) medium (yellow) or high (red) risk of epidemic conditions for scab.
A graph shows the risk probability for the seven days precious to flowering. The
graph information assumes that the current day is the day of flowering. The
next graph shows temperature and rainfall for the last seven days. Click on the
arrow next to view model parameters. That will bring up another bar chart that
shows you the temperature in number of hours/day when it was favorable for scab
(orange bars), the number of hours of rainfall (purple bars) and the number of
hours when both the temperature and the relative humidity were in the favorable
range for scab (blue bars). So, you can determine when conditions were
favorable for scab. Although the model uses temperatures between about 48°F and
86°F, the most favorable conditions for infection are temperatures between
68-86°F, with periods of rainfall longer than 24 hours.
If you are considering a fungicide application as “insurance,” consider whether the yield potential of the field is high enough to justify protection fungicide applications protect the yield that is there, but they don’t make up for a poor stand of wheat. Also consider wheat quality issues and markets. Discount schedules for vomitoxin contaminated wheat vary, but white wheat tends to be discounted with lower ppm of vomitoxin than red wheat. We have four products registered for head scab this year. Folicur 3.6 F, Muscle 3.6F and Embrace 3.6L are all tebuconazoles, and have Section 18 labels. These products can be applied up until wheat has started to flower (Feekes 10.5.1). A new product, Proline is also a triazole, prothioconazole and has a regular label for head scab and foliar diseases. It can be applied up until 50 percent flowering (Feekes 10.5.2). For best results, fungicides should be applied within one to three days after 75 percent of the wheat is fully headed (the entire head emerged beyond the flag leaf). Depending on the temperature, this timing often corresponds to when 25 percent or less of the wheat has begun to flower.
For those of you in the Thumb area who want to have a look
at the DONCast predictions of vomitoxin levels in wheat across the lake in
Ontario, you can access that web site by going to
http://www.weatherinnovations.com/
On the Ontario map, the predicted DON levels for heading on May 31 range from
under 1ppm to around 2ppm.
Ned Birkey
It was cool and rainy over the holiday weekend, then it turned
sunny and hot this week. There are still some fields that are too wet to plant.
Crop reports
Alfalfa cutting is on hold as rain is forecast for the next several days. Alfalfa weevil continues to be over threshold. First cutting quality diminishes daily because of the delayed cutting due to concerns of rain and continued insect feeding. I have not seen any potato leafhoppers, but have not swept fields either. I cannot imagine that they are not here yet.
Barley is of interest to a few farmers in the area. The
straw is sold as a “natural” treatment of pondweeds, at a terrific price.
Corn is mostly green, with some yellow corn also. Ninety-eight
percent has been planted and most fields have emerged. Advanced fields are at
the V5 leaf stage, but most corn is only V2-3. It will be tough to find any
knee high corn by June 4 this year. European corn borer traps will be going up
tomorrow in sweet corn fields in Monroe, Wayne and Washtenaw counties and field
corn in
Soybeans are mostly planted and have emerged this past week. Advanced fields are at the V2 leaf stage. Bean leaf beetles are out and actively feeding.
Wheat is doing great and has withstood the 90-degree temperatures so far, with at least one more day to go before temperatures are forecast to moderate. Most fields are at the critical flowering Feekes’ 10.5.1 stage. Powdery mildew and Septoria can be found, though I have not seen any leaf rust.
Interest in the pre-sidedress nitrate testing program has picked up a bit this spring. I will be making trips to MSU on the next few Wednesdays with soil nitrate samples.
So far, we have a great crop of mosquitoes.
Bruce MacKellar
Weekend rainfall provided some much needed soil moisture in
most of the southwest region. A noted exception to this would have been areas
directly along the
For commercial corn,
the earliest fields are in the 5 collar stage. Rainfall over the weekend seemed
to help with weed control on later planted fields. We do have some grass weed
escapes due to dry conditions after preemergence programs have been applied. Some
glyphosate resistant corn fields are being treated for the first time, with
weeds having become quite sizable in some cases. It is important to limit the
amount of weed competition for corn, controlling weeds before they reach 4
inches in height for the best results, with two passes usually necessary for
excellent control. We are approaching “side-dress mania” time in
Seed corn
planting is wrapping up this week. Stands generally look pretty good with some
of the fields planted just before the storms on May 15 having limited challenges
after the heavy downpours. There were relatively few areas, however, that were
severely impacted from these events. We have seen some challenges on male row
plant stands on some of these areas, but there should be enough to facilitate
pollination on fields that I have looked at. Corn flea beetle feeding remains
an issue. We also should be concerned about the potential for cutworm feeding
activity on later planted seed corn fields. I have caught the first European
corn borer moth at a blacklight trap in the
Soybean planting
is essentially wrapped up in the region. Early planted beans are at the first
tri-foliate stage. Insect damage from bean leaf beetles is common, but below
the threshold of 25 percent or more defoliation throughout field; 50 percent
defoliation of seedlings. Van Buren County ANR Educator Mike Staton reports
heavier feeding in areas of Berrien and Van Buren counties than I have seen in
Alfalfa harvest
is still moving forward around the rain showers. We have had several
established fields that have suffered stand setbacks following the freezes in
April. It remains to be seen if these plants will recover with the second
cutting. Mike Staton reported removing and examining alfalfa crowns on plants
that had gone dormant following the freeze. He found that most roots showed
little signs of crown rot and decay, which provides hope that the plants will
begin to set new growth during the second cutting. We have seen similar
situations in
Wheat is flowering in many fields in the area. (view photo) With wet weather expected over the next several days, producers should monitor wheat for the development of leaf diseases. The potential also goes up for fusarium head blight under extended wet conditions, especially on areas where wheat is following corn in a rotation. Click here to visit the Penn State University Wheat Head Blight Predictive Tool to see what the program says about the potential for fusarium head blight in your area. If you decide to treat your wheat to control or prevent fusarium head blight, review Diane Brown-Rytlewski’s article in the May 7, 2007 Field CAT Alert about guidance on which fungicides may work the best to control the disease. We also need to continue to monitor wheat for armyworms. We also have concerns about leaf diseases on wheat, as powdery mildew can be found on lower leaves of the canopy. Click here for more information on powdery mildew and other wheat foliar diseases.
Fred Springborn
Hit and miss showers across the area gave farmers six to seven days of weather that was conducive to getting field work done, as relatively dry weather persists across the region. Many areas could benefit from a light rain, as the showers that did occur only yielded a few tenths of an inch of rain. High temperatures in the last week have ranged from the lower 70’s to the upper 80’s with relatively low humidity levels.
Wheat is well into or past boot in all fields with heads emerging in several. Few disease problems have been reported or observed at this time, powdery mildew is present in some fields at significant levels on susceptible varieties. Soil moisture is a concern in wheat due to sparse rainfall and high plant usage. Growers are advised to consider timing of irrigation carefully, as it relates to head scab risk. Oats are progressing well, many fields have the first node showing (jointing).
Corn planting is
essentially finished with 99 percent of the crop planted in Montcalm and 95
percent planted as you go north into
Soybean planting is progressing with 90 percent or more of the crop in the ground with several fields emerged with growth up to V2.
Dry bean planting has begun with 5-10 percent of the crop planted with fewer acres anticipated this year.
Alfalfa harvest is underway with 10 up to 50 percent of the crop harvested depending upon the location. A few farms are finished and some have not yet started. GDD41 is well over 750 in all locations in the region. Alfalfa weevils are still active with damage increasing in many fields that have not yet been harvested. Harvested fields need to be monitored for feeding on regrowth. The first adult potato leafhopper was reported in Montcalm on Wednesday, May 30.
Paul Gross
The region received light rains on the evening of Saturday, May 26. The amount varied from three tenths to about one half inch. The rains were just enough to germinate some of the corn and soybeans that were planted into dry soil. Temperatures reached the high eighties on Wednesday. For the most part, our stands are generally good for all crops. Soil moisture is adequate at this time, however a nice warm rain would be welcomed by everyone.
The corn crop is planted with the early planted fields in V-3 toV-4. There are some reports of yellow corn, but for the most part stands are very good at this point. There are some fields that were on the wet side when planted, and there is some side wall compaction. The corn roots are trying to push through. Farmers are making the sidedress nitrogen applications. This is an excellent time to take nitrate tests. Nitrate testing is an excellent way to insure good nitrogen management. With the high prices, this is not the year to over or under apply nitrogen. To test is to know.
Soybeans are planted with emergence generally good. Some of the late planted fields benefited from the rain over the weekend to get them out of the ground. The early planted fields have the first trifoliate leaves out. Growers are encouraged to make timely herbicide applications so weeds do not reduce yield.
The wheat crop is heading with some fields beginning to flower. We are seeing some diseases and the pressure varies from field to field and variety to variety. There is some concern that the forecast for rains over the next few days will make conditions ideal for head scab. Contact your local Extension office for more information.
Alfalfa harvest is under way with farmers a little disappointed with yield. The crop is ready to harvest with PEAQ stick readings at 40 NDF this week. There are fields that are over threshold for alfalfa weevils and should be cut as soon as possible. The re-growth in fields with heavy infestations in first cutting should be scouted for weevil feeding.
Sugar beets are doing very well with good stands and good weed control at this time.
Mark Seamon
Temperatures in the high 80’s and low 90’s are helping crops to put on a lot of growth. The southern Thumb is still challenged with wet soils and continues to delay planting.
Early bud to mid-bud stage describes most fields of alfalfa. Some fields have been cut, but most have not. Yield of the first cutting is reduced from the past couple of years, but is still a good yield. Multiple frost events appear to have slowed growth of this cutting.
Sugar beets are showing good growth and development with warmer temperatures. Weed control in most fields is good. Rhizoctonia control with Quadris may still be considered in areas with pressure.
The wheat crop is
moving through growth stages quickly with high air temperatures. The most
advanced fields are now flowering. Some later planted fields are just showing
head emergence. Planting date and wheat variety are causing most of these
maturity differences. Fungicide applications to protect against Fusarium head
blight should begin in many fields that have full head emergence. The
Corn planting is pretty well wrapped up across the area. Emergence has been challenged with soil crusting in isolated places that received heavy rains before emergence. Most fields are at V1-3. Purpling of some varieties are showing up especially in stressed conditions, such as following sugar beets or crusted soils.
Many growers are well into planting of their soybeans with a few finished. Most emerged soybeans are in the cotyledon or unifoliate growth stage.
Dry bean planting has begun this week with some growers planting a little earlier on the calendar than they would like due to concerns of dry soil. Soil moisture is good at this time, but is changing with the high temperatures.
Jeff
Andresen
Agricultural Meteorology
Geography
An upper air trough across the northern Great Plains the morning of Thursday, May 31, will very slowly move eastward towards the Great Lakes region by the end of the weekend, setting the stage for a couple more days of very summer-like weather with an almost daily chance for showers and thunderstorms. Given the lack of an organized focusing mechanism for convection, any rainfall that develops through Friday will be isolated in nature, with most areas remaining dry. Best chances for rainfall will be during late afternoon and early evening hours. Temperatures through Saturday will range from highs in the upper 70's in lakeshore areas to the upper 80's inland, with lows generally in the upper 50's to mid 60=s.
As the upper air trough approaches this weekend, there will be a better chance for rainfall, especially Saturday night and Sunday, when widespread 0.25-0.50 inch rainfall totals are expected over most of the state. Temperatures will fall back to highs in the 70's by Monday, with lows in the 50's. Cooler, unsettled weather is expected early next week, with the possibility of showers each day through Wednesday.
In the medium range time frame, forecast guidance suggests that upper air troughing will dominate regional weather conditions through the middle to latter part of next week before being replaced by a ridging pattern by next weekend. With the troughing pattern in place, the NOAA 6‑10 day outlook for June 5-9 calls for cooler than normal temperatures and for above normal precipitation totals statewide. During the 8-14 day period covering June 7-13, the outlook calls for mean temperatures to moderate to near normal levels and for precipitation to range from near normal in the Lower Peninsula to above normal in Upper Michigan.
NOAA long lead outlooks for the next few months call for the
gradual development of cooler than normal sea surface temperatures (La Nina
conditions) in the equatorial Pacific. However, any related impacts in the