C.O.R.N. Newsletter 2012-28

Dates Covered: 
August 28, 2012 - September 3, 2012
Editor: 
Rob Leeds

Early September Weather Outlook: Above normal temperatures, rainfall depends on Isaac

The outlook for Ohio calls for above normal temperatures into early September as discussed last week. Normal highs are 75 northeast to 82 southwest with normal lows of about 55-60. Expect most days to have highs in the 80s and lows in the 60s. A few days late this week and next week will likely top out in the 90s with a few days in the 70s especially north for high temperatures. Lows will generally be warmer than normal as tropical moisture tries to move north leaving us in the 60s.

Now for the less confident forecast, rainfall. It all depends on the remnants of Isaac. If Isaac came over Ohio we would see above normal rainfall. Most weather models take it north, west or south so for now we will go with normal rainfall which is near 1.5 inches with a spread from 1-2 inches.  Isolated totals of less than one inch and well over 2-3 inches are possible. The best chance for heavy rain appear to be in the far north. Again, confidence is low in this rainfall forecast. The main rain chances come over Labor Day weekend and later next week

Will August rain influence soybean yield?

 

On average, there are 2,500 to 3,000 individual soybean seeds per pound.  Soybean seeds produced during drought conditions tend to be smaller compared to seeds produced under normal conditions.  Small seed size reduces yield.  The influence of late-season rainfall on yield depends on soybean growth stage.  If soybeans are at the R5 or R6 growth stage (seed filling), August rainfall will increase soybean size.  However, if soybeans are at the R7 growth stage (one normal pod on the main stem has reached its mature pod color), rainfall (or lack of rainfall) will have little influence on soybean yield.

 

More late season soybean diseases

Now is the time to scout fields for soybean disease problems and make plans to reduce there impact next year. Many of these diseases can be prevented by choosing varieties with higher levels of resistance. In some cases, tiling a field to improve drainage or crop rotation will alleviate damage in the future. Here are a few more soybean diseases I found myself or samples were sent in to the lab.

1. Frogeye leaf spot. Higher levels of infection were readily visible in our fungicide trial at Western Research station. Admittedly, we planted a variety that is super susceptible so we can measure efficacy of several fungicides. It is important to look for this now, especially for producers that are in a continuous soybean system. If frogeye is present in any field, one of the keys to management is to not plant a susceptible variety back into that field and preferably it may be time to rotate.

2. SDS and brown stem rot were both reported last week. Foliar symptoms are very similar, one of the key differences is that the internal pith is white with SDS while it is brown for brown stem rot. Soils with low pH can also favor brown stem rot symptom development. It is time to take a soil test on these fields to check for pH for brown stem rot and soybean cyst nematode levels for SDS.

3. Phytophthora stem rot - which is very surprising. In both situations only 1 to 2 inches of rain fell. But it appears that it had nowhere to go with the hard compacted soils. The Phytophthora sojae populations in Ohio have adapted to many of the Rps genes that are used to manage them and the key is to have high levels of partial resistance (also called field resistance and tolerance). If there are high levels of partial resistance then the stem rot phase will not develop in soybeans that are in the reproductive growth stages.

4. White mold. The cool nights that occurred in late July and early August along with the limited rainfall was enough to get this one going. I am not sure how much there is, but I found the first plant at the Western Research Station and another report from northeast Ohio. Choosing varieties with high levels of resistance are an appropriate management strategy for this disease. Resistance to white mold (Sclerotinia stem rot) is not a complete resistance. What you will see is that there will be fewer plants affected in a resistant variety compared to one that is highly susceptible.

5. Soybean virus diseases. Primarily this year bean pot mottle virus which is transmitted by bean leaf beetle and soybean necrotic vein virus have both been identified in several fields in Ohio. Bean pod mottle virus can cause streaking of seed in addition to some yield loss, especially from infections that occurred early in the season. Soybean necrotic vein virus is new, but we have observed symptoms of this virus since 2005 in Ohio. These symptoms are quite different for a virus, they are rusty colored blotches that occur on the leaves, they begin as yellow discoloration with discoloration of the veins on the back of the leaves which progress to rust colored blotches on the upper leaf surface. This is one of the most difficult diseases that I have had to work with and diagnose and the first identification was done at the Univ. of Arkansas. Once the leaves develop the large rusty blotch, the virus is very difficult to detect, this year we received samples in the early stages of symptom development and were able to get a positive diagnostic reaction. There is very little known about this disease, it is thought that thrips can transmit this virus from plant to plant.

6. Soybean rust - it has not been found here this year nor has it ever been found as a sporulating lesion. Numerous fields in the state already have moved into maturing leaves and are beginning to dry down. The hurricane that is currently hitting Florida is expected to move across the area of the southeast that does have soybean rust. The earliest that we could detect rust in Ohio will not be until mid-September and then this is still going to be very difficult with the levels they are reporting out of the southern states. No spraying is required at this time, not even for our double crop soybeans. However, if we do get rains from this hurricane, it would be very nice to gather leaves in mid to late September to determine the distribution and severity of the infection. In 2004, after the first hurricane brought rust to the US, it took until November for researchers to find it and it was not at economically damaging levels at that time. This type of data is necessary to help build models to improve predictions for soybean rust for future years.

Preparation of Storage Facilities for Grain Harvest

After the long, stinking hot, droughty summer, expectations for poor to seriously poor yields are running high.  Thus, protecting every bushel that gets harvested should also be high on everyone's priority list.  Protecting grain quality and ultimately the economic value of the grain begins long before the first acre is ever harvested.  This pre-harvest activity is to prepare grain harvesting, handling and storage equipment and structures for the soon to be harvested corn and soybeans. 

All pieces of equipment used in harvesting the grain should be cleaned, inspected, and repaired several weeks prior to the beginning of the harvest season.  And the harvest season is rushing at us at an accelerated pace this year.  Soybean fields are changing colors and corn kernels are dented and rapidly drying down even though in some fields the stalks and leaves are still fully green.  Like in real estate where the mantra is Location! Location! Location!, the mantra in grain harvesting and handling should be Sanitation! Sanitation! Sanitation!  Starting with thorough cleaning of every piece of equipment through which or in which grain will be passed or hauled.  Remove all traces of old grain from combines, combine heads, truck beds, grain carts, augers, lift buckets, grain pits, grain driers, bins and any other equipment used for harvesting, transporting, and handling grain.  Even small amounts of moldy and/or insect-infested grain left in equipment can contaminate a bin of new grain.

Since grain is usually in contact with grain bins for the greatest length of time, extra attention should be paid to the sanitation of these structures.  Remove any grain or grain dust from inside the bins by sweeping or vacuuming empty bins and brushing down walls.  Pay close attention to cracks and crevices, ledges over doors, and hollow tube ladder rungs on or in which grain could have been trapped from the previous storage seasons.  Fans, aeration ducts, exhausts, and when possible, beneath slotted floors should be cleared of debris as well.  Dispose of all debris in a lawful manner and away from the storage facility.  Sanitation outside of bins is as important as inside of the bins.  Ideally there should be no vegetation (weeds, shrubs, etc.) growing up against the outside of the bin.  Grain pests (insects and rodents) can be harbored in the vegetation.  Bare ground covered with gravel or cement is preferred, but short-mown grass is tolerable. Remove any spilled grain from around the outside of the bin and storage facility.

Once storage structures have been thoroughly cleaned, carefully inspect them for signs of deterioration, especially for leaks and holes through which insects, birds or rodents can gain easy access to the stored grain or rain and snow can drip or blow in onto the grain to produce wet spots that can lead to mold growth. While inspecting for physical problems, one should also test aeration fans and driers for functionality.  Check belts, bearings and gear boxes for wear and proper lubrication.  Check electrical systems for corroded connections and frayed wiring before harvest.  Mice like to nest inside electrical boxes where they are safe from predators.  They will strip insulation from wires for nesting material and their urine causes corrosion. While inspecting control boxes, be sure to seal any openings through which mice could get in.  Be sure that guards and safety shields are in place over belts, chains and intakes.  Seal all leaks and make repairs to the equipment before you need them to manage the grain.

Once all cleaning and repairs have been completed, an empty-bin application of an appropriately labeled insecticide is advisable, especially in bins with difficult to clean areas and/or in bins with a history of insect problems.  For empty-bin insecticide treatments that are applied as a liquid, allow a minimum of 24 hours for the sprays to dry before loading grain into the bin.  It is preferable to have empty-bin treatments applied at least two weeks prior to harvest.

Registered empty-bin insecticides include:  Tempo Ultra SC (cyfluthrin), Storcide II (chlorpyrifos methyl plus deltamethrin), Suspend SC (deltamethrin), Diacon-D and Diacon II (s-methoprene = an insect growth regulator), and several pyrethrin products can be used to apply a surface treatment to the inside of the bin and provide a residual protection.  Other products that contain diatomaceous earth and/or silicon dioxide such as Insecto, Protect-It, Perma-Guard and others may be utilized.  Refer to the individual product labels for lists of insects controlled and application directions.  If a bin is known to be heavily infested with insects, an empty-bin fumigation may be required to knock down insect populations before applying one of the above insecticides.  The most readily available product for this purpose is phosphine gas producing materials such as aluminum phosphide and magnesium phosphide sold under a wide variety of trade names.  Phosphine is an extremely toxic material and fumigations should be conducted by trained, experienced, licensed applicators.

Another measure one might take to reduce the chance of insect infestation is to apply a perimeter spray around the base and up the outside walls of the bin about 15 feet.  This may only be necessary in areas where grain infesting insect movement has been observed on the outsides of the storage bins.  There are several synthetic pyrethroids (cyfluthrin, deltamethrin, permethrin, resmethrin, etc.) that can be used for this purpose as long as they do not come in contact with the grain.

Grain storage insecticide labels tend to change frequently.  As always, check to make sure you are following the instructions on the product label and using the appropriate product for your situation.  One also needs to be sure that the end-user of the stored grain does not have restrictions on insecticide uses on or around the grains that they are going to purchase.  If growing specialty grains, check with your buyers before using insecticides.

A few more words of caution include, new grain should NEVER be stored on top of grain from a previous season's harvest; remove old grain and clean bins before adding new grain.  Grains broken in the harvesting and/or handling process become more susceptible to infestation by insects and mold.  Thus, adjust combines according to the manufacturer's specifications to minimize grain damage and to maximize removal of fines and other foreign material, move grains as little as possible, and limit the number of times and heights from which grains are dropped to reduce breakage.

Last but not least, review your safety procedures for working with flowing grain, grain harvesting and handling equipment, and personal protection.  Anyone who works around the bins and grain handling equipment should know where to find shut-off switches, fire extinguishers, and emergency phone numbers.  Being prepared for harvest will reduce the risk of accidents, and knowing how to react in an emergency can save lives.

 

Plan Last Alfalfa Cutting

Drought conditions, high leafhopper numbers, and a more frequent harvest schedule are common factors for alfalfa fields this year in many parts of the state. All of these factors can contribute to shorter stand life. In general, 5 or more cuttings of alfalfa per year can shorten stand life. Where rainfall has been adequate for growth, growers have harvested on a more frequent cutting schedule this year and are planning to take a fall harvest to boost forage quantity on the farm. The last harvest or cutting date of alfalfa is yet another factor that can influence stand persistence. If stand persistence is a goal, then growers need to carefully plan the last cutting date. According to the Ohio Agronomy Guide, the risk to alfalfa stands is minimized when the last harvest of the year is completed by September 7 in northern Ohio, September 12 in central Ohio and September 15 in southern Ohio. Harvesting later than this can limit the accumulation of carbohydrate and protein reserves that plants need for winter survival and to initiate early growth in the spring.

After that last cutting, growers can do a stand evaluation to assess how their stand has come through this difficult year and what might be expected next spring. Look at the stand density as measured by plants per square foot. The guidelines are:

- Seeding year: 25-30 plants per square foot

- Second year: 10-15 plants per square foot

- Third year and older: 5-6 plants per square foot

Next, dig and count the alfalfa plants in a 1 to 2-square foot area in several random locations in the field. Split open alfalfa roots lengthwise to observe tissue health. In healthy stands, fewer than 30% of plants will show significant discoloration and rot in the crown and taproot, and vigorous crown shoots are symmetrically distributed around the crown. If greater than 50% of the plants show symptoms of crown or root rot, plan to interseed with a legume other than alfalfa, interseed with an improved grass species, or rotate to another crop.

Managing Drought Stressed Hay Fields

The dry weather combined with high temperatures and low humidity across many regions of Ohio this summer has limited summer growth of many hay fields. This is especially true of grass and mixed grass-legume hay stands. There are fields where very little regrowth has occurred since the second cutting. In some pockets of the state, regrowth has been insufficient for hay harvesting since the first cutting taken in May. How should those very drought stressed hay fields be managed where the limited growth present is old and mature now? Will mowing help to stimulate fall growth -- assuming we get sufficient rainfall soon?

I really don’t think mowing will help stimulate regrowth that much, especially in grasses. In alfalfa, mowing off old growth might help a little, but new growth will probably occur from crown shoots regardless of mowing, if the plant is released from drought stress.

With predominant alfalfa stands, if there is enough growth right now to make an economically viable harvest and the alfalfa is dormant and dropping leaves, then cutting and harvesting that forage will gain some salvage feed. Cutting the stand now should not hurt the stand, assuming it has already shut down due to drought stress. If hay harvest is not economical, an option would be to graze the stand, but precautions need to be taken to prevent bloat.

For new seedings of alfalfa or grasses made this spring, I recommend refraining from mowing them if they are severely drought stressed. If weeds are a problem, then consider mowing high to remove seed heads before the seeds mature.

For predominant grass stands that are established, if you don’t get significant rainfall soon, then cutting the crop will likely intensify the stress and could do more damage to the stand. The little bit of growth present is helping to shade the soil surface and preventing even worse drying. The leaf area present is probably transpiring just a little bit in the morning hours, which helps cool the plant. By removing the growth with clipping or mowing, plant transpiration will be reduced, decreasing its ability to cool. The soil will be more exposed to the sun, causing more drying and intensifying the drought stress on the root system and the plant.

If we get enough rain in the coming week or two to stimulate good fall growth of established alfalfa and mixed alfalfa-grass stands, no harvesting should be made until at least mid- to late October. This will allow time for the plant to accumulate the energy reserves needed for winter survival and regrowth next spring. Even, then late fall cutting runs the risk of increases in heaving damage later in the winter, especially on heaving prone soils. I recommend NO fall cutting of new seedings made this spring or late summer.

Finally, autumn is a good time to soil test and add recommended topdress fertilizer to your permanent hay and pastures. This too will enhance plant survival through the winter and productivity next year.

 

Pigweed seed collection and giant ragweed survey – we need your help

1.  Reminder to take our survey about postemergence management of giant ragweed in Roundup Ready soybeans.  The survey found at the following link is brief (10 questions) and completely anonymous:  http://www.surveymonkey.com/s/SFRKY8W.  Thanks in advance for your participation.

 2.  For the past couple of years we seem to be hearing that pigweeds are increasing as a problem in Roundup Ready fields.  We are starting a project to determine whether pigweed populations in Ohio have developed resistance to glyphosate.  The first step of this is to collect seed from any population of pigweed that survived POST glyphosate application in Roundup Ready crops.  This includes redroot/smooth pigweed, waterhemp, or any related species.  We will be conducting some surveys of our own to find these fields, but we need help in identifying suspect fields and collecting seed.  Feel free to contact us with the location of fields that we can sample from, or to collect and mail seed to us.  For the latter, please provide field location and your contact information.  Contact Bruce Ackley for more information – 614-292-1393 or Ackley.19@osu.edu.

 

Summary of Western Bean Cutworm for 2012

As August comes to a close, we have noticed a dramatic decline in the numbers of western bean cutworm moths in our traps. In fact, several locations have not reported catches in over 2 weeks, a clear signal that flight is over. So, with another trapping season finished (our 7th season), what information can we gain regarding its pest status in Ohio?

The total number of catches was 3,114 (see updated map at http://entomology.osu.edu/ag/), which is slightly down from last year. Peak flight was the 3rd week of July, which is slightly early and probably related to the warm temperatures in spring and early summer. However, our key areas including northeast and northwest Ohio continued to have high numbers of moths caught. Additionally, these areas also noticed a small level of egg infestation, although none of the fields were over threshold. While we might find additional evidence of larval feeding once harvest begins, it appears that WBC was not a significant pest yet again. Despite the lack of economic pressure, one result of our trapping is that WBC is not going away-it still remains an important pest of corn that is best managed by adult trapping and egg scouting. Thank you to all the OSU-Extension Educators and Field Specialists for their assistance with trapping this year!

Archive Issue Contributors: 
Archive Issue Authors: 

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.