C.O.R.N. Newsletter 2009-18

Dates Covered: 
June 15, 2009 - June 22, 2009
Editor: 
Jonah T. Johnson

Wheat Scab Update June 15, 2009: Initial Reports Indicate Low Levels of Head Scab in Ohio

Authors: Alissa Kriss, Pierce Paul

Surveys of wheat fields for head scab began in southern counties of Ohio during the first two weeks of June. Counties in central and northern Ohio will be surveyed during the weeks of June 15 and June 22, respectively. The best time to survey for Wheat Scab is during the soft dough stage of wheat development, before the wheat starts turning color. This is approximately 18 to 21 days after flowering. Areas that received frequent rainfall and warm weather during flowering are at the greatest risk for scab development and vomitoxin contamination and should be visited before the wheat dries down to determine if there is scab problem.

Rain events around flowering in Ohio were generally light and scattered, with cool temperatures, which prompted the Wheat Scab Risk Assessment Tool http://www.wheatscab.psu.edu/riskTool_2009.html to show low risk of scab development across the state throughout the flowering period. So far 27 fields have been surveyed and, with the exception of one field, the incidence of scab is very low (< 8%; less than eight scabby heads out of every 100 heads observed) in most fields. The only field with a relatively high incidence of scab (28%) was a field of scab susceptible wheat planted no-till into corn stubble. Remember, the scab fungus, Fusarium graminearum, also infects corn, causing ear and stalk rot. Therefore, planting wheat after corn greatly increases the risk for scab, even when weather conditions are marginally favorable for infection. More corn stubble means more spores are available, and our research shows that higher spore loads lead to higher levels of infection and vomitoxin contamination, even when visual scab symptoms are low.

Selecting varieties that are moderately resistant, planting wheat after soybean, along with a well timed fungicide application is the most effective integrated approach for minimizing yield and quality losses due to scab. A few southern winter wheat states saw high levels of scab this year, but reports are indicating that fields planted with resistant varieties were less affected than those planted with susceptible varieties http://corn.osu.edu/#E.

Winter Storage of UAN Solution – Impacting what is Being Applied Today

Authors: David Henry, Robert Mullen

This spring there have been reports from producers that analysis of urea ammonium nitrate (28-0-0) has revealed a nitrogen (N) concentration of only 20%. Where has the rest of the N gone? The most likely explanation is the over-winter storage of the material. Urea and ammonium nitrate are salts that easily dissolve in water. The amount that can dissolve into a given volume of water depends on the temperature of the water. The warmer the water, the more salt that can dissolve. Once the salt is dissolved, it will stay in solution until it cools down to a critical temperature, for 28% UAN, that temperature is 0°F. When UAN cools to this temperature, some of the urea and ammonium nitrate come out of solution and settle to the bottom of the tank as crystals. If you remember back to this past winter, there several days that dropped into the sub-zero temperatures that may have caused this to happen. If this has happened, the good news is that the N has not been lost; it will take some work to get salt crystals back into solution however. Once the material is warm again (the warmer the better), it needs to be circulated with a pump taking liquid from the top of the tank back into the bottom. This will take 24-72 hours depending on tank size, temperature, and how quickly the pump circulates the solution.

Soybean Aphids in Ohio

Authors: Ron Hammond, Andy Michel, Bruce Eisley

As reported in last week’s C.O.R.N. newsletter, soybean aphids were found on soybean fields to our north in Michigan. Based on these reports, we began checking fields in northwest Ohio and were able to find a few aphids ourselves. Soybean aphids were found on soybeans planted at the OARDC Northwest Research Station south of Bowling Green. Aphids were already producing young aphids, and thus, had been there for a while. Whereas most soybean fields in the area have just emerged, the beans that we found them on were some of the earliest-planted soybeans on the station, and already had two trifoliate leaves. But just today, we searched early planted fields near Wooster, OH, in Wayne County, in the V3 stage, and actually were finding larger numbers of aphids on plants, some plants having nearly 30 aphids per plant. Not all plants had aphids, but many did. With Michigan and Ohio beginning to see colonization, along with having received reports of aphids being found in Indiana, Ontario, and Quebec, it is apparent that soybean aphids have overwintered successfully and are beginning their soybean cycle in the eastern portion of the Corn Belt. Growers might want to begin sampling their own fields, especially ones that were early planted. Let us, or your extension educator know if you begin finding them.

What does this hold for Ohio growers? Having predicted aphid problems this summer, we believe that these early reports of aphids on soybean support this forecast. However, much can happen that can alter the final outcome. Soybean planting is much later this year, which could have a strong influence on their populations. Many fields have been treated with a seed insecticide such as Cruiser, which might alter numbers. Beneficial insects could always come on strong. Thus, numerous factors could play a role in what finally happens later this summer. That is why we recommend that growers plan on scouting all their fields, and only take action if aphid numbers pass the economic threshold of 250 aphids per plant with a rising population. This needs to be done field by field. This is the way of integrated pest management, or IPM. Keep reading this newsletter for further updates.

Late corn and soybean plantings

Authors: Peter Thomison, Jim Beuerlein

Recently, we’ve received questions about the advisability of planting corn versus soybean after mid-June in NW Ohio. These questions have arisen in part because some corn fields need to be replanted due to emergence problems, including soil crusting, possible herbicide injury, etc.
Corn is not recommended as a late crop after mid June. Soybean is an option until early July. Some exceptions to late plantings of corn might be if corn is being grown for silage rather than grain, and N and corn herbicides had already been applied.

Recent studies have shown that good yields are possible with corn planted as late as mid-June but as a rule there’s likely to be greater yield variability with late planted corn than late planted soybean. Moreover, given current corn and soybean prices and production budgets (http://aede.osu.edu/Programs/FarmManagement/Budgets/crops-2009/index.htm) planting soybean is going to be more profitable in most situations.

We can lose as much as 50% or more of our yield potential when corn is planted in the latter half of June (see the Ohio Agronomy Guide online at: http://ohioline.osu.edu/b472/index.html. We lose about 1 to 2 bu/A of yield with every day of delayed planting after the first week of May - with the yield loss increasing more, the later it gets. In late June, there is an increasing risk of the corn crop not maturing before frost - unless growers plant hybrids of considerably earlier maturity than those normally planted. Yields of soybean planted in late June can be as high as 65 to 75% of normal. Effects of soybean relative maturity on grain yield can be large for late plantings. A key consideration in late soybean plantings is planting the latest-maturing variety that will reach physiological maturity before the first killing frost.

Weather conditions, especially adequate soil moisture, often limit the yield potential of late planted both corn and soybeans. However, corn is highly susceptible to drought damage during pollination and early grain fill and the potential for high temperature and water stress typically increases later in the growing season when late planted corn flowers. Because soybeans flower over a longer period, they’re usually less vulnerable to this type of injury. As a result, late planted corn is a riskier crop than soybean. Some other factors to consider with late planted corn include:
• Higher grain moisture that may require artificial drying.
• Lower test weights that may result in significant dockage.
• Greater stalk lodging and stalk rots that may slow harvest and reduce
yield. Late crops may experience more stress during grain fill and
weathering during dry-down.
• Increased injury from silk clipping insects like corn rootworm beetles
and Japanese beetles (and second generation European corn borer
damage, if the hybrids planted are not ECB Bt hybrids).
• Greater foliar diseases injury. Losses to gray leaf spot may increase
with later planting dates.
• Less effective N uptake. If conditions turn dry after planting, late
sidedress N applications may be ineffective.

Scouting for Western Bean Cutworm

Authors: Andy Michel, Ron Hammond, Bruce Eisley

It’s that time of year to plan for western bean cutworm (WBCW) scouting in corn. As most will remember from previous articles the last 3 years, WBCW is a pest of corn ears and dry beans. This was a common pest in the western Corn Belt and only recently expanded its range eastward. In 2006 we caught our first adult in Ohio, and the numbers have been growing ever since, although, thankfully, we have not yet seen eggs, larvae or damage of WBCW. Last year, we caught 150 adult moths, and even 2 as far east as the OARDC in Wooster. While we will focus on biology, damage and control in later issues and on our website (http://entomology.osu.edu/ag/), this week we are making sure growers prepare for adult scouting. Simple and easy milk jug traps are used: cut-out 4 windows on each side, and about 2-3 inches from the bottom. Bend a paper clip into an S-curve, pierce a rubber lure on one end and hang the other end on the inside of the milk jug and re-attach the cap to hold the lure in place. Lures can be purchased from Gempler’s or Great Lakes IPM. Attach the milk jug to a fence post about 3-5 feet high, and place the trap on the edge of a corn field. Use a mixture of 4 parts water to 1 part antifreeze with a drop of dish soap, and fill the bottom of the jug leaving about 1 inch of space. Traps should be placed preferably by June 24th but no later than July 1, and be checked at least weekly. Lures will need to be replaced by the 3rd-4th week. Adult WBCW begin to emerge in late June, with peak flight usually by mid July, and ending by mid August. Ohio State Extension Personnel will be again monitoring for WBCW this year, and weekly updates starting in July can be found in the CORN newsletter and on our website.

So, what are you looking for? Adult WBCW are dark brown and black in color and can be identified by 3 characteristic markings. First, a white stripe is present along the edge of the forewing. Second, a brown dot can be found in the middle of the forewing, and finally a brown crescent is found near the edge. There can be some look-a-likes, and for more information go to our website (http://entomology.osu.edu/ag) or the NC-IPM website for WBCW (http://www.ncipmc.org/alerts/wbc.cfm). Do not assume any moth collected in your trap is a WBCW; you will need to get a correct identification. And, as always, contact your local extension office or entomology state specialists, especially if WBCW are found.

Insect Updates

Authors: Bruce Eisley, Andy Michel, Ron Hammond

While no other insects are causing major concerns at this time, some are producing localized problems. Cereal leaf beetle continues to feed on cereal grains, particularly oats, with numerous oat fields needing treatment. Slugs are causing greater concern, especially in late planted soybeans. Bean leaf beetle has continued to feed on soybean fields; for them, the earlier planted soybeans. European corn borer moths are being observed, suggesting that scouting for first generation should begin shortly. We have even had reports of twospotted spider mites beginning to increase on soybean field edges in areas that have become noticeable drier. Calls on alfalfa weevil causing re-growth problems have come in. Although no reports of heavy potato leafhopper have been received, alfalfa growers should also begin sampling their re-growth. As we head into the summer, growers should keep abreast of the possible pest problems that occur in Ohio.

Weather Update

Authors: Jim Noel

Last week saw less than an inch of precipitation over most areas north of I-70. One to two inches fell in most areas south of I-70. This was slightly below normal since north of I-70 usually experience “normal” rain events around an inch. However, due to the cooler weather, evapotranspiration rates have also been less than normal so things are fairly good at this point.

Rest of June:
Temperatures will be slightly above normal (mostly on overnight lows) and precipitation will be slightly less than normal in most areas. Northwest flow will dominate the next few weeks keeping temperatures overall in check with most highs at or below 90. The exception will be a short term burst of heat Thursday and Friday of this week when highs will reach above 88 degrees.

Summer:
All indications of near normal temperatures and precipitation are intact. This does not mean we won't see short term bursts of extremes but it does not look to be a real hot summer. The latest models indicate a normal temperature for July and then warmer than normal in August then normal in September. As for rainfall, the models now indicate normal for July then below normal in August then normal in September.

Fall:
Indications still are for a possible El Nino which will turn fall and winter warmer and drier than normal. However, this is an early call. We will monitor this in the coming weeks and months. However, this is a possible longer-term pattern change coming!!! A turn to a drier pattern from the overall wetter pattern of 2008 and part of 2009.

Archive Issue Contributors: 

Pierce Paul, Anne Dorrance, and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel and Bruce Eisley (Entomology), Jim Beuerlein (Soybean & Small Grain Production), Peter Thomison (Corn Production), Robert Mullen (Soil Fertility), Jim Noel (NOAA). Extension Agents and Associates: Roger Bender (Shelby), Howard Siegrist (Licking), Greg LaBarge (Fulton), Harold Watters (Champaign), Mike Gastier (Huron), Mark Koenig (Sandusky), Wes Haun (Logan), Jonah Johnson (Clark), Bruce Clevenger (Defiance), Les Ober (Geauga), Steve Prochaska (Crawford), Alan Sundermeier (Wood), Suzanne Mills-Wasniak (Montgomery) and Tim Fine (Miami).

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.