C.O.R.N. Newsletter 2011-14

Dates Covered: 
May 24, 2011 - May 31, 2011
Glen Arnold

Optimizing the profitability of corn planted in June (added May 25)

If switching to soybean and preventative plant crop insurance are not options, farmers need to reconsider their production practices and focus on those that will generate the greatest profits in a late planting production environment. What optimizes yield when corn is planted early doesn’t always have the same effect when corn is planted in June. Given the shorter growing season, the response of a late planted corn crop to certain inputs may be limited compared to responses of a corn crop planted on normal planting dates. Moreover some management adjustments will facilitate more rapid crop establishment and thereby limit further yield losses associated with planting delays.

Consider the following management alternatives so that planting is not further delayed when favorable planting conditions occur and economic returns from various inputs are optimized –

  • Avoid high-end range N rates on corn following soybean. OSU research has shown that nitrogen rates can be decreased by 10-15% with minimal impact on productivity when corn is planted in early June.
  • Side-dress anhydrous N (or UAN liquid solutions) and apply a minimum of 30 lb/N broadcast or banded to stimulate early seedling growth.  If you do not have the capability to apply N with your planter, a surface application of UAN as a herbicide carrier can be a way to carry your corn crop until sidedress N is applied.
  • Place starter applications of P and K in bands two inches to the side and two inches below the seed. Remember application of P and K is only necessary with the starter if they are deficient in the soil, and the greatest probability of yield response from P and K starter is in a no-till situation.  
  • Keep time expended on tillage passes and other preparatory operations to a minimum.  Such work will provide minimal benefits if it results in further planting delays. No-till offers the best option for planting on time this year. Field seedbed preparation should be limited to leveling ruts that may have been left by the previous year’s harvest - disk or field cultivate very lightly to level. Most newer planters provide relatively good seed placement in "trashy" or crusted seedbeds.
  • Switch to an adapted short season hybrid. Although a full season hybrid may still have a yield advantage over shorter season hybrids planted in early June, it could have significantly higher grain moisture at maturity than earlier maturing hybrids if it dries down slowly. Moreover, recent evaluations indicate there are some 100-104 day relative maturity hybrids with excellent yield potential. However performance data for such early hybrids is limited compared to late maturities. For more information on selecting corn hybrids for delayed planting, consult "Delayed Planting & Hybrid Maturity Decisions", a Purdue/Ohio State University Extension publication available online at: http://www.agry.purdue.edu/ext/pubs/AY-312-W.pdf  (Consult “ Table 4. Approximate “safe” relative hybrid maturities for delayed plantings throughout Ohio”)
  • Reassess seeding rates. Soil temperatures are usually warmer in late planted fields, and as a result germination and emergence should be more rapid and uniform. So, as planting is delayed, seeding rates may be lowered (decreased to 3 to 5% higher than the desired harvest population) in anticipation of a higher percentage of seedlings emerging. Past university research indicates that optimal plant populations for early (mid to late April) and late planted (late May to early June) corn are similar. However,  recent OSU studies suggest little benefit from increasing plant populations above 30,000 plants/A in June. This lack of response to final stands over 30,000 plants/A was associated with greater stalk lodging for hybrids planted during June compared to May.


Two-week Weather Outlook

The outlook for May 30-June 5 calls for near normal rainfall (near 1 inch) and above normal temperatures + 3-7F. As high pressure builds aloft rainfall appears less frequent with improving conditions.

Q & A on Foliar Fungicides for Wheat Head Scab Suppression

Q1: Which fungicide is the most effective against scab and vomitoxin?

A1: Based on data from 12 years of scab fungicide research, Prosaro, Caramba and Proline are the top three scab fungicides, providing very similar levels of control.

Q2: What about Folicur and other tebuconazole fungicides?

A2: Folicur and other tebuconazole do provide some level of scab and vomitoxin suppression, but our data show the Prosaro, Caramba and Proline provide between 10 and 15% greater control of scab, and between 20 to 25% greater control of vomitoxin than Folicur.

Q3: Will fungicide application at flowering for scab control also control foliar diseases?

A3: Yes. Both Prosaro and Caramba provide very good to excellent control of foliar diseases. In particular, application at flowering will provide very good control of Stagonospora, a disease that can develop late and affect both grain yield and quality.

Q4: Do I need to mix Prosaro or Caramba with another fungicide to control several other diseases such as powdery mildew, Septoria, and Stagonospora?

A4: No, mixing is not necessary; these fungicides control a wide range of foliar diseases on their own.   

Q5: Will aerial application help to control scab?

A5: Yes, aerial application will suppress scab if done correctly. By correctly I mean if applied at flowering and using a volume of 5 gallons per acre.

Q6: Will application at heading control scab?

A6: Application at full head emergence (Feekes 10.5) will provide some level of scab suppression, but will not give you the best results.

Q7: What about applications after flowering?

A7: Applications made 2, 3, or even 4 days after flowering will also provide some level of scab suppression, but becomes increasingly less effective as you move further away from flowering.

Q8: What is the rainfast time” (“the time required between application and rain for the product to perform effectively”) for scab fungicides.

A8: There is very little or no university data on rainfast time for scab fungicides. However, based on the fact that these products are quickly taken up by the plant, the rainfast time could be considered the time it takes for the product to dry, which is anywhere between 15 minutes and 2 hours, depending on the weather conditions.

Q9: Will a fungicide application at flowering guarantee vomitoxin levels below 2 ppm?

A9: No! There are no guarantees that vomitoxin levels will be reduced below 2 ppm in every situation, especially if conditions are highly favorable for scab and the variety is highly susceptible. However, at this time, a fungicide application is your only option for trying to reduce vomitoxin to some acceptable level.

Q10: Should I prioritize treating fields will susceptible varieties or those with resistant varieties?  

A10: Priority should be given to fields that are flowering, whether or not the variety is susceptible or resistant. No variety is completely resistant or immune to scab. A fungicide application to a resistant variety usually gives better results in terms of scab and vomitoxin reduction than a fungicide application to a susceptible variety.

Q11: Do I really have a 10-day window to apply a fungicide to control scab?

A11: No! You do not. You have at best a 5-day window, if you count a few day before and a few days after the beginning of flowering. The best time still remains at early flowering.

Head Scab Ratings for Wheat Varieties

The annual Ohio Wheat Performance Trials have rated the entries for head scab for many years. You can access 2008, 2009 and 2010 information at http://www.oardc.ohio-state.edu/wheattrials/

The 2010 Yield and Agronomic Characteristics would represent the most severe head scab pressure and represent weather conditions similar to what we are experiencing in 2011. This information can be found at this location http://oardc.osu.edu/wheattrials/regions.asp?year=2010#two

Fungicide applications for head scab suppression need to be made at Feekes 10.5.1, or early flowering. There are several fungicides available for Fusarium head blight control, and these are listed in the foliar fungicide efficacy table developed by the North Central Regional Committee on Management of Small Grain Diseases or NCERA-184 committee: Click this link for a table: http://www.ppdl.purdue.edu/ppdl/wise/NCERA_184_Wheat_fungicide_chart_2010_v2.pdf

Current Insect Conditions and Late Planting Concerns

Slugs – Wet cool springs are often associated with slugs, and obviously these are the conditions we have had.  Of more importance is that while most fields have not been planted, the slugs have hatched and have begun their growth.  Thus, when fields finally get planted, start to germinate, and finally emerge, the slugs will in all likelihood be at a growth stage where their feeding can cause economic injury.  Keep in mind that it is only in fields that have slugs will we see problems.  The weather conditions do not cause slugs to show up.  But when planting late into fields with known slug populations and previous problems, you should plan on monitoring your crops.  Because of the ability of slugs to cause significant problems with soybean emergence, soybeans should be watched closely.  It would be helpful to scout for slugs prior to planting into problem fields by searching underneath crop residue and the top soil level to see if slugs are present.  If necessary, on application of a molluscicide might become necessary.  At this time of year, one thing that you should hope for is warm and dry weather that will help the crops emerge faster and begin quicker growth.  The better the growing conditions the lesser the chances of heavy feeding injury.  See http://ohioline.osu.edu/ent-fact/pdf/0020.pdf for more information on this pest and differences in injury between corn and soybean.

Western corn rootworms – Larvae usually hatch in late May or early June. In general, late planting tends to reduce the likelihood of economic problems of corn rootworms, perhaps because of the lack of corn root development and thus feeding sites for the larvae.  Along with what has appeared to be lower rootworm populations over the last 1-2 years, we would hope for even less injury for this pest this year.  See http://ohioline.osu.edu/ent-fact/pdf/0016.pdf for more information on this insect pest.

Black cutworms – Fields having spring weeds and planted late this spring might be more susceptible to black cutworm injury this year. Corn is at most risk when planted into fields that have large populations of winter annual weeds.  Although we usually see more problems in no-till fields, tillage just before planting will not provide control of newly hatched larvae that are already present; thus, growers should not assume that any late tillage immediately before planting will control this pest over the next few weeks.  And with the larger cutworm populations that we think we have this year, don’t assume that you will get good control from any Bt hybrid that you might have been planted. Large infestations of black cutworms can often overwhelm Bt hybrids.   Also, previous history suggests that the various insecticide seed treatments at either the low or high insecticidal rates do not offer acceptable control.  We recommend that growers plan on scouting for this pest in any late planted fields where weeds were late tilled or in no-till situations.  Rescue treatments are usually the best management tactic if scouting confirms economic populations.  See http://ohioline.osu.edu/ent-fact/pdf/0035.pdf for more information on this insect pest.

European corn borers – This is one insect where late planting tends to increase potential problems with the second generation.  In regular years, we often suggest Bt hybrids specifically for late planted field for control of possible problems.  However, numbers of this insect have been relative low over the past few years, so it remains to be seen how much problem we have this year.  See http://ohioline.osu.edu/ent-fact/pdf/0015.pdf for more information on this insect pest.

Bean leaf beetles and Mexican bean beetles on Soybeans – Early-planted soybean fields are most at risk for early-season feeding by both these insects. Because most soybean planting will be later this season, we don't anticipate large economic infestations across the board with these insects this spring.  However, any soybean fields that did get planted on time that are the only fields emerged in an area should be monitored closely in case those fields act as a trap crop, being the only soybean fields available.  Later planted fields might be another story if we have a build-up of the second generation.   However because the majority of the fields will be later planted, the late summer generation of these two insects will hopefully be distributed over many fields.  See http://ohioline.osu.edu/ent-fact/pdf/0039.pdf for more information on these defoliating pests.

Switching to Soybeans? Some points to consider:

1. For fields that have been continuous corn – target these first!!  The year of soybeans will be great to help give a break to those pathogens that are residue borne.  It will give that corn residue a chance to break down before adding to it.  This is especially important if there has been gray leaf spot, anthracnose, or northern corn leaf spot in the field.

2. For fields that were in soybeans in 2009-2010:  Continuous soybeans leads up to a build-up of both soil borne and residue borne plant pathogens.  The worst culprits are soybean cyst nematode and frogeye leaf spot.  In Ohio, both of these pathogens have contributed to significant yield losses when susceptible varieties were planted in the same field year after year.  Soybean cyst nematode is best managed with crop rotation – primarily a non-host crop such as wheat or corn.  Frogeye leaf spot is managed with resistant varieties – and avoiding planting soybeans in fields that had frogeye the year before.  For those fields where you had been planting soybeans and were switching to corn – avoid switching fields where SCN has reached high numbers.  It is important  to keep the rotation scheme in place.

3. Check the resistance of the variety.  The primary concern here is for Phytophthora root and stem rot.  Not all varieties sold have high levels of partial resistance (tolerance) and unfortunately, these wet saturated soil condition have the pathogen “primed” for when soybeans are in the ground.  For Ohio, varieties with Rps1c, or Rps1k, or Rps3 or Rps6 PLUS high levels of partial resistance are required for optimum stand throughout the growing season.

4. Treat the seed.  Soybeans planted into soils that have been saturated need a seed treatment.  There are a plethora of seedling pathogens in Ohio’s poorly drained fields and they need a seed treatment.  Target products that will manage both the true fungi and the water molds. 

5. From a soil fertility standpoint, switching to soybeans does not represent much of a change in your fertility program.  Anything you did last fall in preparation for this year’s corn will be to the benefit of your soybeans.  If you are breaking a continuous corn system with soybeans (while this may seem a bit early), plan on taking a nitrogen credit next year when you come back to corn.  For those who did apply anhydrous ammonia earlier this spring, soybeans will be nitrogen scavengers in a nitrogen rich environment, so those applications will not adversely impact your soybeans this summer.

This year is starting out to be just as challenging as last year and the seed treatments will make a difference on final stand counts and potentially yields.

Protecting Bees in Ohio

According to Ohio law, if a pesticide is toxic to bees, it is the applicator’s responsibility to contact the beekeepers with registered apiaries (beehives) within ½ mile of the target area if it is more than ½ acre in size and the crop is in flower. The apiary should have the name and phone number of the beekeeper posted. A list of registered apiaries is available through the Ohio Department of Agriculture.

Applicators should avoid spraying when bees are active in the field with flowering crops or weeds. Other times to avoid spraying are from 10:00 a.m. to 7:00 p.m. or when temperatures are above 65 degrees F. On extremely hot days, bees may be active later into the evening.

Follow label precautions that relate to drift and be aware of the potential risk to neighboring crops or areas. Filter strips or other conservation areas that border fields may have flowering plants with foraging bees. Bees have a long range and can forage up to two and one-half miles from the apiary.

White-nose Fungus Infected Bats and Impact on Agronomic Crop Pests

It is feared that white nose fungus will lead to local extinctions.  Losing native bat populations is serious in of itself, but many species provide a valuable service—devouring insects.  Most of what these bats eat include mosquitoes, flies, and even some agronomic crop pests such as European corn borer and various corn rootworm species.

Bats are an important part of a group of general predators that include both insects and vertebrates.  For example, birds have been known to remove corn ear worm or western bean cutworm from infected ears.  While one species of predator may not economically control a pest by itself, the loss of many members of the group of crop pest predators is important and has the potential to decrease natural control.      

A recent article appearing in Science, a well know scientific publication, and placed in numerous newspapers, suggests that the loss of bats due to this disease would cost crop growers billions of dollars across the United States, with the cost to Ohio growers $1.7 Billion.  This article was also summarized and discussed in this month’s Ohio Country Journal.  While this disease is a serious threat to Ohio’s bats, the impact on Ohio’s field crops of that amount is questionable.  The amount of crop loss suggested was based solely on a single study on cotton in southwest Texas with one bat species, the Brazilian free-tailed bat, feeding on one pest species, the cotton bollworm also known as the corn earworm.   While the corn earworm does migrate from southern states and occurs in Ohio, it is mostly a concern on sweet corn and other vegetables. 

The Brazilian free-tailed bat is not found in Ohio.  The potential cost to Ohio’s growers was extrapolated from this single study done in Texas.  And upon reading this study from Texas, most of its conclusions were based on associations between the bat and this one pest, various assumptions, and numerous further extrapolations.  Although the commonly found bats in Ohio are known to feed on crop pests during the summer, none are thought to play a significant role in keeping crop pest numbers down by themselves.  At most, they probably just add to general pest predation from various insect predators including other vertebrates such as birds and various beneficial insects.

Perhaps research in the future might alter our knowledge of this, but at this time, field crop growers should not be overly concerned.  However, as discussed in the first paragraph, bats are an important component of the ecosystem, and this new disease, white-nose fungus, is a serious threat to their survival.

Tobacco Pesticides and 24c Labels

There are two new labels for products that have been used in tobacco production for years.  Ridomil Gold recently received approval with a 24c (special local need) to be used in the setter water at transplanting to aid in prevention of damaging black shank.  This method of application will place the fungicide in the root zone at the time of transplanting. The other 24c label is for Quadris in a greenhouse for controlling target spot on seedlings.

A third 24c is now approved for extending the use of Terramaster for controlling Pythium soft root rot.  The label extends the time that Terramaster can be used in the float beds.  With the forecast calling for continued wet weather, plants may need to be held past the timeline for the current label.  This does not increase the seasonal limits for the amount to be used, but it would extend it past the current 8 weeks after the trays are placed on water.  The 24c label permits the product to be used until within 5 days of transplanting.

Keep in mind you need to have the 24c label with you (in hand) when using such products.  The 24c labels may be found on the Pesticide Education Web Site at http://pested.osu.edu/24C.htm


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About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.