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Ohio State University Extension

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C.O.R.N. Newsletter 2012-20

Dates Covered: 
July 2, 2012 - July 9, 2012
Editor: 
Amanda Douridas

The Weather Pattern Continues

The pattern remains in place through July of above normal temperatures and below normal rainfall. For the first half of 2012, it is almost the exact opposite of 2011. Rainfall was 5-10 inches above normal in 2011 in most places with a few higher totals, while in 2012 rainfall is generally 3-10 inches below normal. Average two extreme years and you get normal. This is why normal is nothing more than a bunch of extremes.

Last week we saw record heat with highs in the 90s to low 100s. We did get some beneficial rainfall late in the week and on the weekend but it came at a price with widespread severe wind damage.

The outlook for the week of July 3-8 calls for much above normal temperatures and near to slightly below normal rainfall. Highs will be in the 90s for much of the state this week with a few places near 100 late in the week or the start of the weekend as the dome of heat re-loads and spreads back east later in the week. Some severe storms can be expected early in the week and again by the weekend. Most places will see rain this week but it will be scattered enough that only small locations will receive 1-2 inches. Most location will see less than an inch which is slightly below normal.

The week of July 9-15 will see a pattern change to not as hot weather with a drier northwest flow. Temperatures will only be slightly above normal with rainfall below normal. Normals are highs in the 80s and lows in the 60s with about an inch of rain typically. Most places will see limited rainfall.

The pattern will likely shift again the week of July 16-22 as a heat dome may develop along the East Coast. This will bring in much above normal temperatures again along with high humidity. However, since the heat dome would be to our east versus west, the return flow around the heat dome will bring our air from the Southeast versus from the Plains. This means chances for thunderstorms again. Expect much above normal temperatures with near normal rainfall for mid July.

The climate models continue to advertise warmer than normal weather into August before a return to normal temperatures for autumn. The drier than normal conditions with some drought would likely persist into August before improvement occurs in August or September with near normal rains returning. We will continue to monitor this change in the coming weeks to gain more confidence in this pattern change by later summer or early autumn.

Western Bean Cutworm Counts on the Rise

Western Bean Cutworm Counts on the Rise

 

Our western bean cutworm catches sharply increased last week, with many of the adults being caught in northwest Ohio.  Although it difficult to use trap counts to predict damage, a general rule of thumb recommends scouting for egg masses when multiple moths are caught over consecutive nights.  A few traps are averaging more than 1 moth caught per night, so egg scouting should begin.  To look for wbc eggs, inspect 20 corn plants in 5 random locations.  Inspect the upper 1-2 most leaves because WBC prefer to place eggs on leaves that are more vertical in orientation. WBC egg masses start out as white, and are laid in clumps of 25-100.  As they mature, the eggs turn tan, and then dark purple.  Egg hatch should occur within 24-48 hours once the eggs turn purple.  Economic threshold is recommended when 5% or more of inspected corn have an egg mass.

            Although we are seeing increased catches, we are probably not at peak flight just yet.  Therefore, scouting for eggs should continue at least until past peak flight (in other words, when the numbers decrease from the previous week).  Because of the heat, we may see peak flight soon, possibly during the 2nd week of July.  If high numbers of wbc egg masses are found, please contact state entomology specialists or local extension educators (we are in the need for egg masses for efficacy work).  

Assessing the Impact of Hot, Dry Weather on Pollination in Corn

 

Although many corn fields in Ohio benefited from much needed rain over the weekend, other areas received little or no rain. According to the U.S. Drought Monitor http://droughtmonitor.unl.edu/DM_state.htm?OH,MW, most of Ohio is experiencing abnormally dry to severe drought conditions. Reports of short, waist high corn tasselling, as well as uneven flowering within fields, are not uncommon in parts of the state which have received negligible rain since early June. Many corn growers want to know what impact drought stress has had on corn pollination, the stage in corn development most sensitive to such stress conditions. When severe drought stress occurs before and during pollination, a delay in silk emergence can occur. Sometimes the length of this delay is such that little or no pollen is available for fertilization when the silks finally appear. When such delays in silking are lengthy, varying degrees of barrenness will result. This year it's likely that silk emergence will be delayed in many drought-stressed corn fields unless we get some significant rain very soon.

There are two techniques commonly used to assess the success or failure of pollination. One involves simply waiting until the developing ovules (kernels) appear as watery blisters (The R2 or the "blister" stage of kernel development). This usually occurs about 1 1/2 weeks after fertilization of the ovules. However, there is a more rapid means to determine pollination success, the ear shake technique.

Each potential kernel on the ear has a silk attached to it. Once a pollen grain "lands" on an individual silk, it quickly germinates and produces a pollen tube that grows the length of the silk to fertilize the ovule in 12 to 28 hours. Within 1 to 3 days after a silk is pollinated and fertilization of the ovule is successful, the silk will detach from the developing kernel. Unfertilized ovules will still have attached silks.

Silks turn brown and dry up after the fertilization process occurs. By carefully unwrapping the husk leaves from an ear and then gently shaking the ear, the silks from the fertilized ovules will readily drop off. Keep in mind that silks can remain receptive to pollen up to 10 days after emergence. The proportion of fertilized ovules (future kernels) on an ear can be deduced by the proportion of silks dropping off the ear. Sampling several ears at random throughout a field will provide an indication of the progress of pollination.

Unusually long silks that are still "fresh" period are a symptom that pollination has not been successful. Unpollinated silks continue to elongate for about 10 days after they emerge from the ear husks before they finally deteriorate rapidly. During this period, silks become less receptive to pollen germination as they age and the rate of kernel set success decreases. If you observe unusually long silks in drought stressed field it may be an indication of pollination failure. 

Dr. Bob Nielsen, the corn extension specialist at Purdue University, recently wrote a good article, ("A Fast & Accurate Pregnancy Test for Corn"), addressing this topic, available online at http://www.kingcorn.org/news/timeless/EarShake.html. There’s also a great video available online at http://www.youtube.com/watch?v=K7DiwD4N0T0&feature=player_embedded

Spray Tank Water Quality

 

Water often comprises ninety-five percent (or more) of the spray solution. What affect might it have on product performance? Research clearly shows that the quality of water used for spraying can affect how pesticides perform.  There are two main water characteristics that can negatively impact the effectiveness of a pesticide application; water hardness and pH.  Pesticides includes: insecticide, herbicides, fungicides, etc.  If the pest is properly identified, the correct product is selected, equipment calibrated, but yet the water quality in the spray tank is poor, the application can be less effective.

Ultimately, the pesticide label is the first place to start to find warnings about spray tank water quality.  For example, the 5 Lb. Dimethoate systemic insecticide (Helena Chemical Co.) label warns: “DO NOT ADD DIMETHOATE TO WATER WITH PH VALUES BELOW 4.0 OR ABOVE 7.0.”  Another example, “The additional of dry ammonium sulfate (AMS)…may increase the performance of this product particularly under hard water conditions.  When using AMS, apply this product at rates directed…lower rates will result in reduced performance.

Numerous water-testing kits are commercially available for both spontaneous and scheduled testing. The kits are readily available, reasonably priced, easy to use and interpret, and reliable. The majority of the test kits use color-changing, sensitive paper to document water hardness, pH, and iron levels.  The pesticide label may be very specific as to the water conditioner and application rate to be used.

In an era of resistant pests to some pesticides, the quality of the spray water needs to be managed to maximize the effectiveness of the product.  It is unknown how often poor pesticide performance is blamed on poor water quality. By testing water sources used for pesticide application for hardness and pH, water quality can be eliminated or considered as a reason for poor pesticide performance.

The Impact of Water Quality on Pesticide Performance – Purdue Extension

http://www.ppp.purdue.edu/Pubs/PPP-86.pdf

Controlling marestail in double-crop soybeans

 

A weed free start is the most critical aspect of a weed management program for double-crop soybeans.  This can be challenging to achieve where glyphosate-resistant marestail are present after wheat harvest.  Problems with marestail include the following:  1) most populations are now glyphosate-resistant and many of these are also ALS-resistant; 2) it’s usually not possible to use 2,4-D ester and wait 7 days until double-crop soybean planting; and 3) marestail that were tall enough to be cut off by harvesting equipment will be even more difficult to control.  Our research indicates that there are no herbicide treatments that consistently control glyphosate-resistant marestail populations that have regrown following mechanical disturbance or prior herbicide treatment.  Certainly one of the best options is to plant LibertyLink soybeans, which allows for a POST application of Liberty to help control plants that survive a preplant burndown.  The following are the most effective burndown options for control of marestail prior to double-crop soybean emergence:

Liberty (32 to 36 oz) + Sharpen (1 oz) + MSO + AMS (can also add metribuzin)

Liberty (32 to 36 oz) + metribuzin (4 to 8 oz of 75DF) + AMS

Glyphosate (1.5 lb ae/A) + Sharpen (1 oz) + MSO + AMS

We suggest using a spray volume of 20 gpa for any of these treatments, and avoiding nozzles that produce large droplets.  Results with a combination of glyphosate and 2,4-D may be more variable then the treatments listed. 

With regard to the control of weeds that can emerge after double-crop soybean planting, and the entire weed control system, the following approaches can be considered.

1.  Plant any type of soybean, and include a residual herbicide with the burndown treatment so that POST herbicides are not needed.  A good strategy in Roundup Ready or nonGMO soybeans even where POST treatment is needed, since POST marestail control might be impossible in these systems.  Residual herbicides used at this time of the year should be restricted to those that have little or no carryover risk – such as metribuzin, Valor, or low rates of chlorimuron or cloransulam products.

2.  Plant a LibertyLink soybean, and apply Ignite POST as needed.  Probably the best option for control of later-emerging marestail or plants that regrow after the burndown, assuming that there is any Liberty available.

3.  Plant a Roundup Ready soybean and apply glyphosate POST.  Should work for most weeds, but not a good choice if the POST application needs to control marestail.

4.  Plant a nonGMO soybean and apply conventional POST herbicides (Flexstar, Fusion, Select, etc) as needed.  This system has the most potential for soybean injury, but seed may be cheaper than the other systems.  Not a good choice if the POST application needs to control marestail.

 

New Soybean and Small Grain Extension Specialist

New Soybean and Small Grain Extension Specialist

I am very excited to join the Agronomic Crops Team as the soybean and small grains specialist.  I am a faculty member with extension and research responsibilities in the Department of Horticulture and Crop Science in collaboration with the Ohio Agricultural Research and Development Center.  In May 2012, I earned my PhD from Michigan State University in Crop and Soil Sciences.  At Michigan State, I held a part-time extension appointment and conducted research in the areas of soil fertility and weed science.  I received my BS and MS from School of Environment and Natural Resources at The Ohio State University.  I look forward to interacting with growers, contributing to the C.O.R.N. newsletter, and participating in extension programming.  I can be contacted by phone at 614-292-9080 or by email at lindsey.233@osu.edu.  My office is located at Room 230 Kottman Hall, 2021 Coffey Road, The Ohio State University, Columbus, OH.

 

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Crop Observation and Recommendation Network

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.