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FieldWatch® – Before You Spray

Wed, 04/18/2018 - 10:32

Before making pesticide applications this year check the FieldWatch® online registry so you are aware of sensitive crops and beehives in the area. In 2017 the Iowa Department of Agriculture and Land Stewardship Pesticide Bureau received a record number of complaints regarding pesticide applications. Taking the time to review what is near a field prior to applications can help mitigate future problems.

FieldWatch® features a voluntary mapping tool through Google Maps™ that shows pesticide applicators the locations of registered sensitive crops and beehives so they can make informed decisions regarding potential pesticide applications. FieldWatch® replaced the Iowa Department of Agriculture and Land Stewardship Sensitive Crop Directory in 2017.

Recently FieldWatch® launched two new mobile apps that make it easier to access and input data. The FieldCheck app is designed to give applicators easier access to information from their mobile device while in the field. BeeCheck is designed to help beekeepers make changing the location of beehives easier and faster. Both apps are available free of charge for Android and iOS devices.

Android FieldCheck for applicators BeeCheck for beekeepers iOS FieldCheck for applicators  BeeCheck for beekeepers

Producers can register their sensitive crops on the DriftWatch Specialty Crop Site Registry and beekeepers can register their hive locations on the BeeCheck Apiary Registry.

Category: Pesticide EducationTags: pesticide applicationsensitive cropsbeehivesFieldWatchapplicators

A Late Spring - Nitrogen Considerations

Tue, 04/17/2018 - 13:34

Winter seems to be never ending, and spring not arriving. This could lead to a compressed period for field work before corn planting begins. There are conversations underway about switching planned spring preplant anhydrous ammonia to another nitrogen (N) product like urea-ammonium nitrate solution (28 or 32% UAN) or granulated urea. And likely discussions about changing from preplant to sidedress applications. What should be considered? Perhaps the most important item is to have a conversation between dealer and farmer to ensure product availability when desired, equipment needed for application, and any associated change in costs.

Preplant Applications

Urea, urea-ammonium nitrate solution, and other products

If planned N fertilizer applications can be made without an undue delay in planting, then go ahead and make the applications. For materials such as urea or UAN solution, or polymer coated urea, those can be broadcast and incorporated with normal tillage before planting. Incorporate or inject rather than leaving the fertilizer on the soil surface to avoid volatile N loss from granulated urea or urea in UAN as it converts to ammonium, or runoff if a rapid rainfall (or snowmelt) event occurs. If time is critical and UAN application is to be made with preemerge herbicides, then surface application is an option, although more risky due to potential volatile N loss from being sprayed/broadcast and the applied N remaining on the soil surface (especially in no-till) if there is not sufficient rain to move the urea into the soil. A rainfall of at least 0.25 to 0.50 inch within approximately two days after application will eliminate volatile loss concern. UAN is half ammonium nitrate and half urea, therefore volatile loss potential from UAN is half of that with urea. Banding UAN on the soil surface will also reduce volatile loss to about half that with broadcast application. Predicting the amount of volatile N loss is difficult, but increases with high surface crop residue (especially no-till), moist-to-drying soils, warm soil temperatures, many days without rainfall, high soil pH, low soil cation exchange capacity, and higher N application rates. Although an added cost to decrease risk of volatile loss, a urease inhibitor can be added to slow urea conversion which provides time for rainfall to move urea into the soil. Preplant or preemerge applications can be part of a weed-and-feed or split-N system, with a full N rate or rate to supply part of the total N application need and the remainder applied sidedress.

Another fertilizer option is polymer coated urea, designed to delay urea release until soils warm. To avoid product runoff, incorporate into the soil. Surface broadcast options, especially adapted to no-tillage that generally do not have volatile loss concern, are ammonium nitrate and ammonium sulfate. These products are not used extensively in Iowa as a primary N material, so would likely have limited availability.

If disturbing soil is a concern in no-tillage from injecting N, then broadcast application is an advantage but also has the large disadvantage of potential volatile losses, surface runoff, or immobilization of N with surface residue, and is not a highly recommended application.

Anhydrous ammonia before planting

Anhydrous ammonia has certain considerations. It must be injected, and the ammonia band will initially have high pH and considerable free ammonia which can damage (burn) corn seedlings and roots. There is no exact “safe” waiting period before planting, and injury can happen even if planting is delayed for a considerable time period. The risk of ammonia injury depends on many factors, with several that are not controllable. Risk increases if application is made when soils are wet and then dry (ammonia moving up the injection track), with higher application rates, when soils with high clay content are wet (sidewall smearing of the injection track and ammonia moving toward the soil surface during application), and when soils are very dry and coarse textured (larger ammonia band). A few management practices can reduce the risk of ammonia damage. Wait and apply when soil conditions are good, have a deep injection depth (six to seven inches or more), or wait several days until planting. If the injection placement relative to future corn rows can’t be controlled, apply at an angle to reduce entire sections of corn rows from being damaged. If the injection track can be controlled with GPS guidance positioning technology, then offset a few inches from the future corn rows – with this guided system no waiting period is needed. There would be a similar free ammonia and/or salt issue with shallow banded urea or UAN solution. Anhydrous ammonia nitrifies more slowly than products like urea or UAN solution, so is a preferable fertilizer for soils with greater potential for losses in wet conditions.

Sidedress Applications

Best options for sidedressing, in approximate order from most to least preferable (and depending on crop emergence and size):

  • injected anhydrous ammonia, UAN, or urea.
  • broadcast granulated ammonium nitrate or ammonium sulfate.
  • surface applied urease inhibitor treated urea or UAN.
  • surface dribble UAN solution.
  • broadcast urea.
  • broadcast UAN.

There is a wide time period for sidedress applications. Sidedress injection can begin immediately after planting if corn rows are visible or GPS guidance positioning equipment is used. Be careful so that soil moved during injection does not cover seeded rows or small corn plants. It is easiest to inject in the row middle and there is no advantage in attempting to place the injected band close to the corn row. Corn roots will reach into the row middle at a small growth stage. Injected N can also be applied between every-other-row, and this will provide equivalent response as when placed between every row. For many soils, when planting corn after soybean there can be adequate N in the root zone to meet the needs of small corn plants. For corn after corn, there is a greater likelihood that additional N is needed for early growth. Preplant or starter N can help meet early plant needs, and is especially important if sidedressing is delayed significantly or there will be a planned mid-to-late vegetative growth stage application in either rotation.

With sidedressing, a urease inhibitor with surface applied and non-incorporated urea and UAN could help reduce volatile loss, similar to that described above with preplant applications. A dry soil surface may be more common within the growing season, which will reduce volatile loss potential. The rate of N applied, and hence the amount of potential N loss, has to be large enough to offset the inhibitor cost. Rainfall will eliminate volatile loss and is needed to move surface applied N into the root zone.

Broadcasting granulated urea, ammonium sulfate, or ammonium nitrate across growing corn can cause leaf spotting or edge browning where fertilizer granules fall into the corn whorl. Damage will be greatest with ammonium nitrate, but that product is not readily available or used in Iowa, with damage from ammonium sulfate more than urea. The chance of damage increases with larger corn and higher application rate. As long as the fertilizer distribution is good, not concentrated over plants, and the rate reasonable, the leaf damage should only be cosmetic.

Broadcast application of UAN solution across growing corn has the potential to cause leaf burn and reduced early growth. Depending upon the severity of damage, reduced plant growth may be visible for several weeks after application. Research conducted in Minnesota indicated that when corn plants were at the V3 growth stage (vegetative leaf stage defined according to the uppermost leaf with a leaf collar visible – in this case three leaf collars visible), phytotoxic effects were worse at rates greater than 60 lb N/acre (rates applied were 0, 60, 90, and 120 lb N/acre), but damage was not permanent and did not adversely affect stand or yield. When plants were larger than the V3 stage, plant damage was worse and some yield depression occurred with the 120 lb N/acre rate. Many herbicides are applied using UAN as the carrier to minimize trips across fields. However, this strategy is only recommended prior to crop emergence. Almost all herbicides prohibit application in N solutions after corn has emerged. Check herbicide labels closely.

If N is going to be sidedress applied, then rates can be adjusted from results of the late spring soil nitrate test (LSNT). Soil samples, 0-12 inch depth, are collected when corn is 6-12 inches tall with rate adjustment based on the measured nitrate-N concentration.

If corn becomes too tall for normal sidedress equipment, it is possible to use high clearance equipment to apply N. The N source often will be UAN solution, with equipment available to either dribble the solution onto the soil surface with drop tubes or shallow inject with coulter-shank bars (coulter-disk injected), and urea which can be broadcast spread across the top of corn.

Research in Iowa has shown corn can respond to N application at mid-to-late vegetative corn growth stages when there is deficient N supply, but there can be loss in yield potential. Reduced yield occurs more frequently when soils are dry at and after application (applied N not getting into the root zone) and with severe N stress. Best responses occur with sufficient rainfall shortly after application to move N into the active root zone.

If attempts to get N applied preplant or early sidedress have failed, or there are concerns about N supply from early fertilizer or manure applications, then mid-to-late vegetative stage application can be a helpful rescue. Having some non-N limiting (approximately 50% more than normal rate) reference strips or areas in fields are helpful for comparisons. These areas can be used to visually determine if corn would respond to additional N, as a check to see if earlier N applications are not sufficient, and determine if plants are showing growth or coloration symptoms that are not due to N deficiency. These reference areas are also needed for N stress sensing tools (such as chlorophyll meters, active canopy sensors, or satellite images) to help guide application rates and understand N stress across landscapes. These reference areas should be planned and N applied early in the season, or be field areas that are known to be non-N deficient. Plant and canopy sensing can begin when corn is at approximately the V8-V10 growth stage. If late N application is needed, it should be applied as quickly as possible and not later than the tassel/silking stage.

In Summary
  • Fertilize before planting if it does not greatly delay corn planting; otherwise consider split or sidedress N.
  • If you decide to change planned N applications, make certain needed N fertilizer products and sidedress or high-clearance equipment will be available; or if hiring applications the dealer/custom applicator can accomplish the applications.
  • Consider the N volatilization potential of different N materials when applying without incorporation or injection into the soil.
  • Try not to make poor N management decisions just to get applications completed.
  • Communication between farmer and dealer is key.
Crop: CornCategory: Soil FertilityTags: Spring Fertilizationnitrogennitrogen managementsidedress N

Corn Row Spacing Considerations

Mon, 03/12/2018 - 15:42

Corn row spacing and plant population have been the focus of many studies throughout the years in an effort to identify ways to increase yields and minimize production costs. Many studies have shown that there was a yield increase going from a 40-inch row spacing to a 30-inch row spacing. Studies had varying results when it comes to less than a 30-inch row spacing. In some cases, row spacing has had no effect on yield whereas others have seen anywhere from a 2-7% increase in yield by narrowing row spacing from the more common 30-inch.

Since 2009, there have been 10 site-years of research trials done in western Iowa looking at the interaction of row spacing and plant population. The objective of this article is to compare various trials to better understand row spacing effects on yield across a broad range of environments. The results from this data suggest that there is a slight yield advantage to 20-inch row spacing compared to 30-inch. In 50% of the site-years, corn planted at a 20-inch row spacing yielded 4.8-15.9 bu/ac more than the 30-inch row spacing.  The remaining 50% had no yield difference between 20- and 30-inch row spacing. This serves as a reminder that growing season and hybrid can significantly influence row spacing effect on yield.


Figure 1. Corn yield response for 20-inch and 30-inch row spacing for ten site-years in northwest Iowa from 2009 through 2016. The solid line is the 1:1 yield line.

Corn row spacing, plant population interactions were evaluated across the 10 site-years and there was no significant interaction. In other words, the recommended plant populations for Iowa are around 34,000-37,000 plants per acre, and these plant populations would not need to be changed if row spacing was reduced from 30 inches to 20 inches.

Rapid canopy closure is one attribute of narrow row spacing that has multiple benefits including inhibiting weed emergence and reducing soil moisture evaporation while increasing light interception. However, there are disadvantages that largely center on equipment setup and capital expenses. In  20-inch row spacing, tire spacing is often adjusted for tractors and sprayer operations to help control traffic between the rows, both in and out of the growing season. In some instances, especially with high clearance sprayers, a narrower tire is desired to minimize traffic on the corn row (i.e. increase the margin for error). The major capital equipment expense is not just the upfront cost of the planter, additional expense is needed for a combine head.

Equipment costs should be taken into account and balanced against the returns from a possible yield increase half of the years and a negligible difference in yield for the remaining years. With the likelihood of improving soybean yields with narrow row spacing, it may be worthwhile to have equipment, such as a split-row planter, that can be used to plant both corn and soybean thus helping to mitigate the cost.

In conclusion, 20-inch row spacing in corn has shown to provide a comparable yield and even a yield advantage to the typical 30-inch row spacing. If narrow row spacing is feasible, there could be benefits for both corn and soybean yields, as well as benefits for weed control and soil moisture retention. Narrow row spacing will require alterations to existing equipment or alternative methods for harvesting and possibly pesticide applications.



Farnham, D.E. 2001. Row Spacing, Plant Density, and Hybrid Effects on Corn Grain Yield and Moisture. Agron. J. 93:1049-1053.

Licht, M., E. Wright, M. Baum, and N. Upah. 2017. Corn planting decisions: What’s changed and what’s the same? Integrated Crop Management Conference, Iowa State University, Ames, IA. 29-30 Nov 2017.

Porter, P.M., D.R. Hicks, W.E. Lueschen, J.H. Ford, D.D. Warnes, and T.R. Hoverstad. 1997. Corn response to row width and plant density in the Northern Corn Belt. J. Prod. Agric. 10:293-300.

Widdicombe, W.D., and K.D. Thelen. 2002. Row width and plant density effects on corn grain production in the Northern Corn Belt. Agron. J. 94:1020-1023.

Crop: CornCategory: Crop ProductionTags: Cornrow spacingcorn management

Consider 15-inch Row Spacing in Soybean

Thu, 02/22/2018 - 09:02

Row spacing is a management decision that often comes up as a priority for achieving high-yielding soybean. Research across the Midwest over several years has consistently shown that soybean planted in narrow rows (<30 inches) has a yield advantage compared to wide rows (≥ 30 inches). The primary reason for this advantage is light utilization; canopy closure is approximately 15 days earlier in 15-inch rows compared to 30-inch rows. Canopy closure earlier in the growing season results in greater light interception and higher growth rates. 

Planting date can influence the potential advantage of narrow rows. Planting in late April or early May will result in higher yields than planting in late May or June regardless of row spacing. However, narrow rows tend to have an advantage over wide rows even in late-planting situations because they are able to capture available sunlight more quickly. Still, this advantage will not fully compensate for the yield penalty of late planting.

Since narrow-row soybean reach canopy closure quicker, it becomes more competitive with weeds, preventing weeds from germinating once the canopy closes. As herbicide resistance continues to spread, the increased competitiveness with narrow rows is an alternate selection pressure of weeds that will help preserve the value of herbicides. This aspect of narrow rows could result in cost savings in your weed control program. Rapid canopy closure can also help reduce soil moisture loss and erosion.

Alternatively, having narrow-row soybean can present some challenges. For example, how will herbicides, insecticides, and fungicides be applied without driving on rows? Ground applications can be made perpendicular to the row. This tends to be effective for applications earlier in the season while aerial applications should be considered for fungicide and insecticide applications later in the season.

A skip-row planting system may prove to be an effective option if aerial application is not desirable. Skip-row planting is effective because it does not plant wheel track rows, making it possible for ground applications all season long while providing much of the yield advantage of narrow row spacing.

Equipment expenses are not trivial. Justifying the cost of a narrow-row planter for a single crop may not be feasible. This is the dominant reason farmers choose not to plant narrow row soybean. One option is to invest in a split-row planter, which works with both corn and soybean for the appropriate row spacing needed for each crop. Additionally, more recent research has shown that corn yields in 30-inch and 20-inch row spacing are similar 50% of the time and benefit the 20-inch row spacing the remainder of the time for currently available genetics and management practices. This opens the possibility of achieving higher yields and profit margins in soybean years while at least maintaining the status quo in corn years.

Keep in mind that narrow-row soybean is vulnerable to many of the same yield-limiting factors that wide-row soybean encounter. If brown stem rot, soybean cyst nematode, or white mold are issues in your fields, narrow-row soybean will be affected more severely. In fact, white mold may be more problematic in narrow row soybeans. If white mold has been consistently problematic in your fields, consider alternative management strategies.

In conclusion, narrow-row spacing can give your fields a yield advantage due to rapid canopy closure resulting in better light utilization. Other potential benefits include less moisture loss, better weed control, and reduced erosion. Applications of insecticides, fungicides, and herbicides should be made in a way that works with narrow row spacing. Be conscious about past yield-limiting factors, such as brown stem rot, soybean cyst nematode, and white mold, and choose a variety that will appropriately fit your cropping system.

Figure 1. Effect of row width on soybean yield from experiments in Iowa. Source: De Bruin and Pedersen, 2008; Swoboda et al., 2011.


Debruin, J.L. and P. Pedersen. 2008. Effect of row spacing and seeding rate on soybean yield. Agronomy Journal 100:704-710.

Elmore, R.W., R.S. Moomaw, and R. Shelley. 1990. Narrow-row soybean. G90-963. NebGuide, University of Nebraska – Lincoln, Lincoln, NE.

Swoboda, C.M., P. Pedersen, P.D. Esker, and G.P. Munkvold. 2011. Soybean yield response to plant distribution in Fusariumvirguliforme infested soils. Agronomy Journal 103:1712-1716.

Wright, D., A. Lenssen, and V. Schmitt. 2013. Intermediate row width can increase soybean profits.

Crop: SoybeanCategory: Crop ProductionTags: Soybeanrow spacingsoybean management

Frogeye Leaf Spot Fungicide Resistance Confirmed in Iowa Soybean

Mon, 02/19/2018 - 09:37

Plant pathologists at Iowa State University and University of Kentucky have confirmed that isolates of Cercospora sojina, the pathogen that causes frogeye leaf spot of soybean, have shown resistance to quinone outside inhibitor (QoI, strobilurin) fungicides in Iowa.

Frogeye leaf spot (Fig. 1) occurs across the United States, and significant yield loss can occur when this disease is widespread within a soybean field. Plant pathologists estimate that this disease was responsible for more than 17.5 million bushels of lost yield, valued at $158.1 million, across the U.S. in 2015. 

Figure 1. Frogeye leaf spot is a common foliar disease in Iowa, appearing as gray lesions surrounded by a reddish-brown border on soybean leaves. 

The pathogen that causes frogeye leaf spot is genetically diverse, which is an important reason why fungicide resistance can occur. This genetic variation increases the chance of selecting for resistance. C. sojina resistance to QoI fungicide was first documented in Tennessee in 2010 and has been detected in several other states since then including those that border Iowa. Isolates of C. sojina were sampled from multiple locations across the state in 2017 and were tested for resistance using established laboratory protocols at the University of Kentucky. All samples evaluated were found to be resistant. The C. sojina isolates from Iowa in 2017 are the first reported to have QoI fungicide resistance in the state.


One method of frogeye leaf spot management and subsequent yield protection has been the application of foliar fungicides during soybean pod development. However, overuse or misuse of fungicides can result in decreased management efficacy if targeted pathogens acquire resistance to a fungicide.

An integrated method of frogeye leaf spot management that does not rely solely on fungicides should be employed. Farmers should consider other disease management practices such as crop rotation, planting of frogeye leaf spot-resistant cultivars, and application of fungicides with multiple modes of action.

Fungicides are very important for disease management, and it is critical to preserve the usefulness of these crop protection tools. Fields should be scouted approximately two weeks after fungicide application to determine if the fungicide is working. If you believe fungicide resistance may be an issue in your field, contact an Iowa State University Extension and Outreach specialist. For resources on fungicide resistance, visit the Take Action website.

Funding for this research has been provided by the Soybean Checkoff through the Iowa Soybean Association and United Soybean Board.

Crop: SoybeanCategory: Plant DiseasesTags: fungicide resistancesoybean diseasestrobilurinQoldisease management

Should We be Spraying Fungicides on Corn at V12?

Thu, 02/08/2018 - 12:39

In 2017, we tested several foliar fungicides on corn at six locations in Iowa: ISU Northwest Research and Demonstration Farm (NWRF), Sutherland; Northeast Research and Demonstration Farm (NERF), Nashua; Northern Research and Demonstration Farm (NRF), Kanawha; Southwest Research and Demonstration Farm (SWRF), Lewis; Southeast Research and Demonstration Farm (SERF), Crawfordsville; and the Ag Engineering and Agronomy (AEA) Farm, Boone.

The purpose of these trials was to help farmers determine if foliar fungicides should be incorporated into their production. Our objectives were:

  1. Assess the effect of application timing of fungicides on disease.
  2. Evaluate the yield response of hybrid corn to foliar fungicide application.
  3. Discern differences, if any, between fungicide products.

Products used and application timings tested
In 2017, eight products were tested (Table 1). The timing of application varied by product and was suggested by the companies contributing each product. Fungicides were applied at growth stage V5, V12, R1, and V5 + R1. This was the first year we have tested applications at V12. No surfactant was included in applications made at V12.

Effect of product and timing on GLS
Disease severity in the lower canopy (below the ear leaf) and upper canopy (ear leaf and above was assessed around R5 (dent). The most prevalent disease in our trials was gray leaf spot (GLS), which was present at four of our six locations (Table 1). At NRF there was no GLS; and at AEA, gray leaf was present at extremely low levels.

Table 1. Effect of Fungicides on GLS in Iowa in 2017

  • There were few differences in GLS control among the products.
  • Significant differences (P>0.1) were observed between times of application.
    • Confirming observations from similar trials done previously, the amount of GLS observed throughout the canopy at R5 between V5 applications and the non-sprayed check did not differ.
    • R1 applications significantly reduced GLS at R5 compared to the non-sprayed check.
    • V12 applications were most effective at reducing GLS severity at R5. In some cases (e.g., at NERF), they were even better at reducing GLS than an application at R1.This was consistent across all four locations.

Based on these data, should we be spraying at V12?
I think the jury is still out on this, but I spent a lot of time thinking about why a V12 application was so effective at reducing GLS in 2017. Two factors come to mind:

  • GLS always starts in the lower canopy. It is likely that the fungicide at V12 reached and protected the lower leaves of the canopy. When applications are made at R1, less product reaches the lower canopy which is obstructed by the leaves of the upper canopy.
  • The V12 applications coincided with warm (80s) and very humid growing conditions (Figure 1). Warm temperatures (75-85F) and high relative humidity (>85% for several hours) favor GLS infection and disease development (Rupe et al. 1982). Consequently, I would argue that the V12 applications in our trials were perfectly timed for the 2017 season and delayed GLS development in the lower canopy, and consequently throughout the season.

Figure 1. Maximum and average relative humidity at ISU research farms from July 1 through 30 August. 2017.  Green shading indicates dates when V12 or R1 foliar fungicide were applied.

These data suggest that an application at V12 improved GLS control for the 2017 season, which had conditions favorable for GLS development. It will be interesting to see if V12 applications are as effective at reducing GLS in future growing seasons that are likely to have different environmental conditions throughout the season.

Also, remember there are other foliar diseases such as northern corn leaf blight or southern rust that may affect corn in Iowa. Since both of these diseases may occur anywhere in the canopy, it is possible that a V12 application may have less effect. A V12 application only protects those leaves that are present at the time of application.

What about yield?
No effect of product or timing was detected on yield at any location (P>0.1; (Table 2). Yields in the trials were excellent. GLS severity in the upper canopy of the non-sprayed controls was low (<10 %) at all locations, suggesting GLS in the trials was not severe enough to influence yield.

Table 2. Effect of Fungicides on Corn Yield in Iowa in 2017

A word of caution
In our trials we did NOT use an NIS in our V12 applications. Adding a surfactant to fungicide applications between V12 and VT may affect ear development (Stetzel et al. 2011).

Thank you to the farm managers and staff at each location who managed the trial and applied the fungicides.

Rupe et al. 1982. Influence of Environment and Plant Maturity on Gray Leaf Spot of Corn Caused by Cercospora zeae-maydis. Phytopathology 72:1587-1591.
Stetzel, N., Wise, K., Nielsen, B., and Gerber, C. 2011. Arrested ear development in hybrid corn. Purdue Extension publication, BP-85-W, 2011.




Crop: CornCategory: Plant DiseasesTags: gray leaf spotfoliar fungicides

Downwind Buffers and Susceptible Crop Restrictions for New Dicamba Products

Sat, 01/13/2018 - 09:26

In response to problems with off-target movement and injury associated with dicamba applications on dicamba-resistant (Xtend) soybean, the EPA made significant changes to labels of the new dicamba products.  While much of the discussion has focused on the Restricted Use designation and the requirement for applicators to receive dicamba-specific training, the EPA also clarified how downwind buffers and protections of susceptible crops are to be implemented.

Downwind buffers  The labels state that a 110 ft downwind buffer must always be maintained from the field edge (a 220 ft buffer is required if a rate greater than 22 oz of Xtendimax w/VGT or FeXapan w/VGT is used). There are four areas that can be included in the buffer distance when they are directly adjacent to the field:
1) roads, paved or gravel surfaces,
2) planted ag fields planted to crops tolerant to dicamba (e.g. grasses, Xtend soybean),
3) ag fields prepared for planting, and,
4) areas covered by buildings or structures with walls and or roof.

The implication of this restriction is that in most situations, a portion of the field will need to be left untreated due to the downwind buffer (Figure 1).  The EPA has clarified that the vegetation in the area between a field edge and a road is not considered part of the road; thus, if the wind is blowing toward a road, the buffer needs to be established in the field regardless of what is found in the field across the road.  It does not matter whether the roadside vegetation is maintained with mowing or other management practices.  

If permanent, perennial vegetation is present between two adjacent fields a downwind buffer will be required.  The label states that downwind buffers are required at field edges; thus, perennial vegetation found in terraces and waterways within fields do not require buffers.  

Figure 1.  Influence of wind direction on restrictions regarding downwind buffers and susceptible crops when using dicamba on dicamba-resistant soybean.

Susceptible crops  The labels state do not apply the product when wind is blowing towards adjacent susceptible crops.  Soybean varieties without the dicamba-resistance trait are considered a susceptible crop; thus, users of the new dicamba products will need to determine whether soybean planted in adjacent fields are dicamba-resistant or not.  The label does not specify a minimum distance required between treated fields and susceptible crops; however, a susceptible crop immediately across a road would be protected.  

The requirements for downwind buffers and protection of susceptible crops add to the complexity of using dicamba in dicamba-resistant soybean.  Users of the products need to carefully evaluate all fields prior to spraying season to determine where downwind buffers may be required and if susceptible crops are present in adjacent fields.  Restrictions for downwind buffers and susceptible crops are not affected by wind speed; thus, they are required even with low wind speeds.  The labels restrict applications to periods when winds are at least 3 MPH and less than 10 MPH.

The 2,4-D products registered for use on 2,4-D resistant corn and soybean (Enlist One and Enlist Duo) also have requirements for downwind buffers and susceptible crops.  However, the downwind buffer with the 2,4-D products are 30 ft rather than 110 ft specified for dicamba products.  The products can not be applied if the wind is blowing towards commercially grown tomatoes, grapes, cucurbits or other fruiting vegetables.  Soybean varieties that do not possess the 2,4-D resistant trait are not considered a susceptible crop.  At the time of publishing this article, Enlist soybean have not been approved for import by China.

Crop: SoybeanCategory: WeedsTags: dicambaherbicide driftherbicide applicationXtend soybeandicamba resistant soybean

New Dicamba Labels Issued

Wed, 01/10/2018 - 16:29

In October 2017, the Environmental Protection Agency reclassified Engenia®, FeXapan™ herbicide Plus VaporGrip® Technology, and Xtendimax® With VaporGrip® Technology as Restricted Use products and added additional restrictions and requirements to their use. One of the additional requirements stated that anyone wishing to apply these products must attend a dicamba or auxin-specific training. Recently, the Iowa Department of Agriculture and Land Stewardship issued Sec. 24(c) Special Local Need labels for Engenia®, FeXapan™ herbicide Plus VaporGrip® Technology, and Xtendimax® With VaporGrip® Technology. The 24(c) labels require all applicators that intend to apply these products to attend an Auxin Herbicide training that has been approved by the Iowa Department of Agriculture and Land Stewardship Pesticide Bureau and offered by a registered Auxin Herbicide training provider. The Agribusiness Association of Iowa is hosting a website, dicambatrainingiowa.org that will list the dates, times, and locations of programs that have been approved by the Iowa Department of Agriculture and Land Stewardship. The information listed will be updated as training programs are approved.This website also provides additional information related to the regulations of dicamba-based products for use with dicamba-resistant soybeans. Applicators must retain records that show they attended an IDALS approved auxin training prior to use of the product. Auxin training is not required prior to purchase or sale of Engenia®, FeXapan™ herbicide Plus VaporGrip® Technology, and Xtendimax® With VaporGrip® Technology in Iowa.

Crop: SoybeanCategory: Pesticide EducationTags: pesticide labelpesticide trainingdicamba resistant soybean