C.O.R.N. Newsletter 2011-24

Dates Covered: 
July 26, 2011 - August 2, 2011
Editor: 
Amanda Douridas
Status of Western Bean Cutworm in Ohio: Scout for Egg Masses

Status of Western Bean Cutworm in Ohio: Scout for Egg Masses

Adult moth captures increased dramatically in the past week, and we are over 2,000 total moths for the season.  Sharp increases were seen in northwest and northeast Ohio.  Additionally, some egg masses were found in Fulton County, although no fields that were visited were over threshold.  This is the second year that egg masses and larvae were detected in corn in this area.  Based on trap counts and temperature, we are probably in peak flight right now.  Therefore, this is the critical time period for western bean cutworm oviposition and infestation.  There is a fair amount of pre-tassel corn, which is the preferred oviposition host for females, and these fields should be scouted for egg masses.  To scout corn, choose 20 consecutive plants in 5 random locations.  Look for a cluster of eggs that are white or purple in color on the uppermost 1-2 leaves.  Corn that is waist or shoulder high, and about 2-4 days from full tassel emergence are at highest risk and should be the priority for scouting.  Economic threshold is at least 5% of corn infestation (the fields inspected in Fulton last Thursday were all 1% or less). 

High temperature effects on corn

The recent heat wave has generated many questions about the impact of high temperatures on corn yields. The “good news” is that corn originated as a tropical grass and can tolerate exposures to adverse temperatures as high as 112 degrees F for brief periods. Optimal daytime temperatures for corn typically range between 77 degrees F and 91 degrees F. Growth decreases when temperatures exceed 95 degrees F. Fortunately, the high temperatures during the past week have been associated with some much needed rains across the state.

How high is too high for corn? Dr. Emerson Nafziger, University of Illinois agronomist notes that “afternoon temperatures in the mid-90s are not a problem for corn… if they have enough soil water available. In experiments, plant temperatures have been raised to 110 or higher without doing direct damage to photosynthetic capacity. The level required to damage leaves depends on the temperature the leaf has experienced before, but it generally takes temperatures above 100 in field-grown plants.”

According to Iowa State University agronomist Roger Elmore and climatologist Elwynn Taylor, the current heat wave may have a double impact on the Iowa corn crop (that is also applicable to Ohio’s corn although the development of the Ohio crop is well behind that of Iowa’s). “The first is the increase in rolling of corn leaves in response to moisture deficiency. By rule-of-thumb, the yield is diminished by 1 percent for every 12 hours of leaf rolling - except during the week of silking when the yield is cut 1 percent per 4 hours of leaf rolling. ….The second impact is less obvious initially. When soil moisture is sufficient, as it is for the most part this July, the crop does not have a measurable yield response to one day of temperatures between 93 F to 98 F. However, the fourth consecutive day with a maximum temperature of 93 F or above results in a 1 percent yield loss in addition to that computed from the leaf rolling. The fifth day there is an additional 2 percent loss; the sixth day an additional 4 percent loss. Data are not sufficient to make generalizations for a heat wave of more than six days, however firing of leaves then becomes likely and very large yield losses are incurred.  Generally a six-day heat wave at silking time is sufficient to assure a yield not to exceed trend (Iowa trend yield is near 174 bushels per acre). Should warmer than usual nights continue for a six-week period the state is assured a below trend harvest….”  

References

Elmore, R. and E. Taylor. 2011. Corn and “a Big Long Heat Wave on the Way” Iowa Integrated Crop Management Newsletter Iowa State Univ. http://www.extension.iastate.edu/CropNews/2011/0715elmoretaylor.htm

Nafziger, E. 2011. High Temperatures and Crops. University of Illinois http://bulletin.ipm.illinois.edu/article.php?id=1537

Temperatures in the 90s and Corn Diseases

It has been way too hot even for corn diseases, but the forecast is for temperatures in the low-to-mid 80s by the end of this week. Most of the foliar diseases of greatest concern in corn in Ohio develop best under cooler conditions than those we have had over the last few weeks, so although it has been humid and even wet in some locations, the level of disease has been very low across most of the state.

All stages of pathogen growth and disease development require temperature and moisture within a favorable (optimum) range. Temperatures above or below these ranges may cause disease development to slowdown or even stop. For instance, gray leaf spot (GLS), one of our most important foliar diseases of corn, develops best at temperatures between 70 and 86 F under high relative humidity or foggy conditions for extended periods during the day. At temperatures above 85 F, several processes important for infection and disease development, including spore production, spore germination, and fungal growth slowdown or stop, even if moisture is present. This results in fewer new infections. In addition, GLS lesions already present on the leaves will stop growing or expanding or will do so at a much slower rate at very high temperatures. Our research shows that it takes GLS lesions a longer time to expand at temperatures above 90 F than at temperatures between 77 and 86 F. Northern corn leaf blight (NCLB), another important foliar disease in Ohio, requires even cooler conditions than GLS. It develops best at temperatures between 66 and 80 F. Common rust requires even cooler conditions, between 60 and 74 F                

Most of the May-planted corn is now beyond silking (R1), and corn planted in June is between late V stages and R1 in some parts of the state. Some of these later fields may be at greater disease risk as temperatures drop over the next week or so, especially if the hybrid is susceptible and the humidity continues to be high. Continue to scout fields for foliar diseases before making a decision to apply fungicides. These decisions should be made on field-by-field basis, with special attention to corn-on-corn, river bottom fields planted to susceptible hybrids. These fields may have been exposed to wetter and cooler conditions (especially in the evenings and early mornings) than fields in other parts of the state, and as such, may be at the greatest risk for diseases such as GLS and NCLB.         

Leaf cupping and wrinkling in soybeans

We have received a number of calls about cupping or wrinkling of soybean leaves, and it seems that this has become an annual issue in much of the cornbelt. Some of the symptoms are undoubtedly due to drift or volatility of herbicides due to the many windy days this year, but some are due to other problems as well. A number of factors can cause these symptoms, and it can be difficult to pinpoint the exact cause. Some additional information on this issue follows. There is also a fact sheet with color photos available from the University of Wisconsin, “Dicamba Injury to Soybeans”, which can be downloaded from:  http://ipcm.wisc.edu/Publications/tabid/54/grm2id/32/Default.aspx.

One of the first herbicides to get blamed in many fields is dicamba, which may have been applied in a nearby corn field. Products containing dicamba include Banvel, Clarity, Marksman, Celebrity Plus, Northstar, Status, Yukon, and numerous generic products. Exposure of soybeans to low concentrations of dicamba through drift or volatility, or even dicamba residues in spray tanks may be the culprit in some fields. The potential for volatility varies among these products, but all can drift if applied during windy conditions. However, many of the affected fields seem to be far enough away from treated corn fields, or dicamba was not used in the area, and this possibility can be ruled out. The most typical symptoms from exposure of soybeans to dicamba are puckering of the new leaves that are emerging 7 to 10 days after exposure. This may be accompanied by stunting of the plant. Soybeans may show these symptoms on several trifoliates, and then recover completely. Spray particle drift from Distinct and Status application often causes more severe symptoms than dicamba alone, due to the diflufenzopyr component of Distinct. However, there is little risk of volatilization of diflufenzopyr, while dicamba can volatilize readily depending upon formulation and temperature.

Research indicates that soybean yield is not generally reduced when minor symptoms occur, and yield loss is more likely if soybeans are in the reproductive stage at the time of exposure (although still unlikely unless symptoms are severe). Our research with postemergence soybean herbicides indicates that soybeans can tolerate considerable early-season injury with little or no impact on yield, when rainfall and other environmental conditions are generally favorable for crop growth after the injury has occurred. Yield loss seems to be most likely when herbicides are applied after about the beginning of July, and soybeans are small at the time of application (which might occur from late planting or poor early-season growing conditions). Where this has occurred, soybeans may not recover well enough to attain the size needed for maximum yield potential.

Over the past decade, we have heard reports of and observed fields where leaf puckering or cupping was uniform over the entire field. Other fields have shown symptoms only in some areas. In OSU research plots, we have occasionally observed puckering in Roundup Ready soybeans following application of glyphosate. Spider mites and leafhopper have been known to cause cupping and wrinkling of soybean leaves. Many of the fields with puckering were previously treated with a postemergence herbicide other than glyphosate. ALS-inhibiting herbicides seem to be most often used in fields with the symptoms, but other herbicides have also been used. One working theory about these symptoms - when the postemergence herbicide causes injury to the terminal buds on soybeans, apical dominance is altered, and plant hormones are redistributed within the plant. The result is the appearance of injury that is similar to that from plant growth regulator herbicides (dicamba, 2,4-D). New shoots may occur at nodes below the injured zone, the plant may take on more of a bushy appearance, and leaves may be wrinkled and cupped. However, most of the fields have not exhibited the increased "bushiness" that might occur if apical dominance was lost.

While herbicides may be responsible for some of the puckering, cupping, and wrinkling that has been observed, we suspect that environmental conditions and soybean variety may have a significant role. This is based on the observation of uniform cupping in fields where no postemergence herbicide was used. Some varieties may be more likely to show symptoms than others. We have not been able to come up with a good explanation for this phenomenon. However, the good news is that leaf cupping and wrinkling generally should not affect yields, and soybeans generally compensate well from other herbicide-related problems given enough time and moisture.

An on-line source to help improve your soybeans

Ohio soybean producers and their retail dealers or crop consultants can sign up for the on-line publication Plant Management Network (PMN). The Plant Management Network is a not-for-profit, online publishing effort whose mission is to enhance the health, management, and production of agricultural and horticultural crops. PMN achieves this mission by developing science-based resources that help researchers, crop management professionals, consultants, growers, educators, and students make better plant management decisions and recommendations. One area I like for soybean information is Focus on Soybean: http://www.plantmanagementnetwork.org/infocenter/topic/focusonsoybean/, a couple of their latest webcasts include yellow flash, volunteer corn control and how to join the 100 Bushel club.

The United Soybean Board is offering free subscriptions to the Plant Management Network’s suite of applied crop management resources, which can be used by soybean growers and consultants to further increase yield and protect their crops.  The Soybean Checkoff helps fund Focus on Soybean. Much of the information in PMN is subscription content.  But thanks to the Soybean Checkoff and United Soybean Board, 500 free Plant Management Network subscriptions are being offered on a first-come, first-serve basis.  You can sign up through the link: http://www.plantmanagementnetwork.org/subscriptions/activation/default.cfm?ID=114343

Cover Crop Decision Tool Available

The Midwest Cover Crop Council (MCCC) Cover Crop Decision Tool is a web-based system to assist farmers in selecting cover crops to include in row crop rotations.  The free web-based program is available at http://www.mccc.msu.edu.

The Cover Crop Decision Tool is an initiative by the MCCC to consolidate cover crop information by state to help farmers make cover crop selections at the county level. Information for each state/province is developed by a team of cover crop experts including university researchers, Extension educators, NRCS personnel, agriculture department personnel, crop advisors, seed suppliers and farmers. The team reviewed and refined information from the Sustainable Agriculture Research and Education (http://www.sare.org) publication Managing Cover Crops Profitably, 3rd edition, to refine application within their state/province.

The information and ratings contained in the Cover Crop Decision Tool is the team consensus based on literature, research results, on-farm experience and practical knowledge.  Information is given for considerations for using the cover crop in each location which include: Planting, Termination, Performance and Roles, Cultural Traits, Potential Advantages and Disadvantages. 

Cover Crops are also rated for adaption to:  

Nitrogen Source: Rates legume cover crops for their relative ability to supply fixed N. (Nonlegumes have not been rated for their biomass nitrogen content, so nonlegumes will not be displayed.)

Nitrogen Scavenger: Rates a cover crop’s ability to take up and store excess nitrogen. Bear in mind that the sooner you plant a cover after main crop harvest—or overseed a cover into the standing crop—the more N it will be able to absorb.

Soil Builder: Rates a cover crop’s ability to produce organic matter and improve soil structure. The ratings assume that you plan to use cover crops regularly in your cropping system to provide ongoing additions to soil organic matter.

Erosion Fighter: Rates how extensive and how quickly a root system develops, how well it holds soil against sheet and wind erosion and the influence the growth habit may have on fighting wind erosion.

The Cover Crop Decision Tool is a project of the MCCC. The MCCC is a diverse group from academia, production agriculture, non-governmental organizations, commodity interests, private sector, and representatives from federal and state agencies. The MCCC collaborates to promote the use of cover crops to address soil, water, air, and agricultural quality concerns in the Great Lakes and Mississippi river basins. MCCC member states/provinces include Indiana, Michigan, Ohio, Manitoba, Ontario, Illinois, Wisconsin, Minnesota, Iowa, and North Dakota.

Oats, planted late, perhaps our most dependable forage?!?!

Oats, planted late, perhaps our most dependable forage?!?!

Most know that for the past nine years, we've spent much time in Fairfield County investigating the virtues of oats as an annual forage when they are planted during mid to late summer, or even into early fall. Based on our experience with oats planted after wheat harvest each of the past 9 years, if you can utilize a forage for grazing, hay, or silage late this fall, oats appear to be the most productive, highest quality, least cost option available to Ohio livestock producers. In fact, if planted most any time in July or August, there's an opportunity to 'create' on a dry matter basis anywhere from two to five tons of forage while investing little more than the cost of 80-100 pounds of oats and 40 pounds of nitrogen.

While we've harvested from 2 to 5 tons, and consistently realized average yields of 3+ tons of dry matter from oats planted in July and August after a harvested wheat crop, it's also apparent that yield and quality can vary greatly as planting date, nitrogen fertilization, and perhaps even oat varieties differ from each field planted.

For those looking to grow a cost-effective alternative forage crop yet this summer, and who have wheat stubble available, based on our experiences with summer planted oats since 2002, Curt Stivison, who initiated this work in Ohio, and I offer these suggestions:

* Optimum planting date for oats from the perspective of yield is not until the first of August. Early August plantings also have resulted in the highest total amount of TDN produced per acre. Later plantings will be slightly higher in quality, but typically not enough to offset the yield advantage of early August planting. While being more conducive to a mechanical harvest in early fall, planting in early July reduces both yield and quality. The earlier oat plantings also have exhibited more susceptibility to rust.

* Regardless the planting date, or variety, no-tilled seeding rates of from 80 to 100 pounds of oats have consistently resulted in optimum forage yields.

* Optimum nitrogen application rate has been 40 to 50 pounds per acre. This application not only produces the highest yields, but at current values of nitrogen, it's also the most cost effective rate. Higher rates of nitrogen actually appear to depress yields based on our 2008 plot results.

* In our plots, bin run oats originating in Canada have outperformed and provided similar quality at harvest as certified Armor oats.

* The optimum combination of productivity and quality of August planted oats arrives 60 to 75 days after planting. Oats planted in July mature more quickly and thus, rapidly decline in quality beginning 50 to 60 days after planting. However, oats will continue to grow after frost, typically until late November or December around most of Ohio.

* Oats harvested 50-60 days after planting and while still in the boot stage of maturity may offer some regrowth that could be grazed later.

* A weed control application of glyphosate is a necessary and cost effective practice prior to oat planting.

An additional advantage observed when using oats for an annual forage crop is the opportunity to capture the total tonnage produced with a single harvest cutting if grazing is not an option.

As oat harvest options in November are considered, grazing provides the most effective and affordable alternative. In 2002, locally the Wolfingers strip grazed oats all winter and actually began the calving season on them before they ran out in mid March.

Baling oats in the fall has been done around Ohio, but it's a challenge considering that oats only dry about half as fast as grass hay. Cut in November, that typically means at least two weeks or more to cure them. Wet wrapping them is an expensive alternative. Using an in-line bale wrapper/tuber is a little less expensive per ton than individually wrapped bales if the equipment is available locally.

Oats won't die until temperatures have been in the mid 20's for several hours. That means they'll still be green and alive in December most years in Ohio. When they finally freeze, and if it's not a wet winter, growers may be able to let them dry out standing, get a few days of dry frozen weather in January, mow them, rake them and bale them quickly after they've essentially dried and cured standing.

In Canada, growers have sprayed their oats with glyphosate and let them dry down while still standing. Then, after a few weeks and at a time when they get a dry week, they mow, rake and bale them all in a day or two. Locally, that's been done once which allowed the oats to be baled in late December and January.

If grazing standing oats is not an opportunity, perhaps chopping and ensiling oats is the best alternative for harvest. This offers several advantages over baling or wet wrapping. Obviously the issue of curing the plants for dry harvest becomes a moot point. Chopping and ensiling into either a permanent structure or bags is also likely less expensive than wet wrapping individual bales. Perhaps even better, as detailed by Francis Fluharty a few years ago in this publication, chopped forages are 30% more digestible than long stem forages.

Admittedly chopping and ensiling is likely more expensive than rolling dry hay, but when you consider you get essentially no storage losses, the timeliness of harvest which is afforded, and the more digestible feed which results, it's a good alternative. And if you're able to bunk feed the chopped and ensiled oats, there will be no "bale ring" feeding losses to be experienced.

If you've yet to attend any of our field days to see for yourself the results of summer seeded oats, this web link has photos and data of several of the past years' efforts as we explored the alternatives described above:

http://beef.osu.edu/beef/graze/wntrgraz.htm.

Soybean diseases – issues at flowering

The vast majority of soybean fields in the state look great – even in the hot weather.  Many fields had their first flower and others are already close to waist high so they are moving in the right direction.  Some problems that we found last week in the field include:

1.         Phytophthora stem rot – plants dying with Phytophthora were identified in several areas of the state last week.  The key here is to look at fields that received heavy >2 inches of rain the week before.  Plants will appear wilted at first with the chocolate brown canker moving up the stem.  This is an excellent time to examine your fields for this disease to see if the resistance package is what you need for your fields.  Plants with low partial resistance/field resistance will be the only ones developing the stem rot.  You will be able to tell if you need a better resistance package for that field.

2.       Soybean cyst nematode – those SCN hotspots can be found in fields which are impacted by drier conditions – low rainfall and heat.  The plants appear stunted and on the roots we found the white pearls (SCN females).  So this is a good time to look at the fields for stunted soybeans.

3.      Nutrient issues related to poor root development.  I had three samples in one day – all with similar symptoms – leaves with manganese type deficiencies coupled with brown “speckles” spots all over the leaves.  Roots were poorly developed, the nodules were dead.  If these fields get some rain they may recover.  One sample was wrapped in a wet paper towel and actually grew new roots during shipment here to Wooster.

Manure Science Review- August 16th

Manure Science Review- August 16th

August 16, 2011, De Graff, OH.  Join us at the Winner Family Dairy to learn about changes in their manure management practices and other options for efficiently using manure nutrients while protecting water quality.  Continuing education hours for CCA's, CLM's, and PE's available. Visit http://www.oardc.ohio-state.edu/ocamm/images/MSR_2011.pdf for registration information.

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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.