C.O.R.N. Newsletter 2004-40

Dates Covered: 
December 6, 2004 - December 21, 2004
Editor: 
Harold Watters

Wheat Yellowing in Areas of Northern Ohio

Authors: Patrick Lipps

We have received reports and samples of wheat plants showing extreme yellowing of the older leaves from fields in northwest and northeast Ohio over the past several weeks. Reports indicated that the wheat emerged well and was green until about four weeks ago. In most locations the wheat continued to look worse over time, but in a few locations the wheat appeared to recover some during the third week of November. Sufficient samples from problem farms have been sent to us to evaluate the fungi associated with the roots. So far we have been able to do the analysis on 6 fields from Van Wert and Paulding counties. Our isolations from roots and crowns of affected plants have yielded a number of Fusarium graminearum isolates, but we have also gotten a few Rhizoctonia isolates as well from four of the six fields.

The recovery of Fusarium graminearum from these young plants indicates that this is the major cause of the root and crown rot disease that is evident in these fields. Please note that Fusarium graminearum is the cause of Fusarium head scab of wheat. This disease was very common in Ohio during the 2004 season. Head scab results in infection of the kernels, some of which are shriveled causing low test weights whereas other seeds appear normal, but have the fungus growing on them. In a C.O.R.N. newsletter article written after wheat harvest (http://corn.osu.edu/index.php?setissueID=50#F) we warned growers about the problems associated with planting seed from fields with Fusarium head scab. This fungus is known to be seed borne and precautions need to be taken when processing seed from scab affected fields. Even though the seed is properly cleaned it is still very important to treat the seed with fungicides that are highly effective against Fusarium on the seed.

In general seed that has the fungus on the surface of the seed will germinate and produce a seedling, but if the conditions in the field become stressful, the seedling will begin to show symptoms of seedling blight. The seedling bight phase of scab is sometimes seen when seed is planted into dry soil, but at other times cold temperature stress, or heavy rains that cause saturated soil conditions cause plant stress and retard root growth. Each of these conditions can impact the amount of symptoms and seedling blight. The important point is that since the plant has little resistance to infection by Fusarium as a seedling, it has to outgrow the infection by producing new roots. Weather or soil conditions that lead to retarded root growth leads to increased vulnerability and more disease. Differences in the amount of seedling blight from one field to the next can sometimes be traced to growing conditions associated with individual fields. These could be shallow planting of seed, dry soil, too much surface residue, heavy rain with saturated soil, planting too high a seeding rate, compaction or even imbalanced fertility. It is frequently very difficult to sort out what actually happened in a field as compared to neighboring fields that look better.

A few words about fungicide seed treatments: One reason we always recommend using fungicide seed treatment is that the grower does not always know the risk of seed infections or seedling diseases before planting. Cleaning seed thoroughly to remove shriveled and light weight seed is extremely important. Also using the proper fungicide materials is important since all fungicides do not have the same efficacy. When Fusarium is known to be present on seed it is important to use the higher labeled rates of certain products and use products that are specifically effective against Fusarium. We commonly recommend applying Thiabendazole (TBZ) in addition to the normal fungicide seed treatment because it is highly effective against Fusarium on seed. Combination products with two fungicides, one being a broad spectrum fungicide like Thiram, also contribute to effectiveness. Uniform application of the treatment on each and every seed along with use of rates effective against Fusarium are also very important.

There is absolutely nothing the grower can do right now for these fields. It is likely that plants showing browning of leaves will continue to die over the winter because they are stressed. Probably the best approach is to forget about these fields until next spring. After the majority of the fields have begun to green up the total damage to the field can be assessed. If plants begin to green up and there looks like a sufficient stand to provide a reasonable crop, then make your top dress nitrogen application as usual. If large areas of the field have dead plants then consider converting the field to another crop.

First Year Western Corn Rootworm Sampling

Authors: Ron Hammond, Bruce Eisley

Personnel from Ohio State University Extension sampled for first-year, western corn rootworm adults (FYWCR) in soybean fields for the eighth year. The final data from the 2004 rootworm trapping program have been assembled. This is an overview of the results from that survey. Sampling was done using Pherocon® AM yellow sticky traps placed in 78 fields in 19 counties. Six traps were placed in the soybeans on metal posts at canopy height and located at least 100 feet from the field edge and evenly spaced in the field. The traps were initially placed in fields as early as July 20 and removed as late as mid September. Traps were serviced once a week throughout the 6 to 7 week survey. A new, clean trap was installed to replace the insect and debris covered, week old trap at the end of each week of trapping. After each trapping week, the number of beetles collected were summed and divided by the number of traps (6) and the number of days the traps were in the field resulting in the average number of beetles collected per trap per day. Research indicates that catches in soybean of 5 or more beetles/trap/day during any trapping week indicates a potential problem with rootworm in the field the following year.

The trapping data from 2004 had the following results:

Three fields had an average > 5 beetles/trap/day
Seven fields had an average between 4 and < 5 beetles/trap/day
Six fields had an average between 3 and < 4 beetles/trap/day
Eight fields had an average between 2 and < 3 beetles/trap/day
Twenty fields had an average between 1 and < 2 beetle/trap/day
Thirty-four fields had an average < 1 beetle/trap/day.

The fields that had > 5 beetles/trap/day were in Allen, Defiance, and Hancock Counties. Last year, none of the fields surveyed ever had > 4 beetles/trap/day. In addition to sampling with the sticky traps, this was our second year to sweep soybean fields in 9 counties along the Ohio-Indiana border for FYWCR adults during the 2nd week of August. Twenty sweeps in 5 places in 2-3 fields per county were taken. The contents of the nets were bagged and then counted in the lab. Sweep net samples do not tell us if a field has a high enough FYWCR adult population to warrant treatment the next year, but they do tell us the relative abundance of the beetle population. The number of FYWCR adults per 100 sweeps ranged from 0 to 51. Although populations were not as high as fields in states to our west, they were higher in 2004 than last year in Ohio.

So What Does This Mean?
Based on the potential treatment level of 5 beetles/trap/day during any trapping week, if any of the three fields with over 5 beetles/trap/day are planted to corn in 2005, a treatment of either a soil insecticide, Poncho 1250 or Cruiser CRW seed treatments (the highest rate of each), or a YieldGard Rootworm transgenic corn should be considered for control of rootworm. These data from both sampling procedures do not mean that other fields in a county that were not sampled do or do not need treatment but it does give good information about the fields that were sampled and about the abundance of the beetles this year. Overall, rootworm populations continue to be relatively low. However, some soybean fields did have populations sufficient to warrant treatment next spring, and suggest that perhaps first year western corn rootworm is increasing in soybean. Because of this possibility, the need to continue sampling for western corn rootworm adults in soybeans in 2005 is great.

Soybean Rust – the Rumors Abound…..

Authors: Anne Dorrance

Asian soybean rust has been verified in at least 9 southern states when I wrote this, all of which appear to have begun, courtesy of hurricane Ivan. Interestingly very few of these positive finds are on the alternate host kudzu and the finds have all been in areas where it is not expected to survive the winter. If those areas have a normal winter and the temperatures drop below freezing the rust will likely be killed. I’ve spoken with some of the folks who have been searching for rust, it is not in every field, in some cases it is very hard to find, and in one case it was only on old beans – not the young volunteers that had recently emerged. This is good news for us. Due to the breadth and distribution of these introductions it not possible that rust came in on ships with soybeans as some have proposed.

It was very clear at a meeting I attended last week, that very little is known about this strain of rust, how long it will take to germinate on a leaf, how long it will take to penetrate the leaf and how many lesions it will take before a leaf is defoliate. Much of the information is based on speculation and not scientific studies. From older studies, this fungus has many similarities to other rust diseases and it is fitting those patterns.

What was very clear is that fungicides do work. And if this rust like other rusts, we in the northern part of the soybean belt are looking at probably not more than 1 to 2 sprays. For areas of Brazil where the infections start early in the vegetative phase, the reports are that they are only putting on 3 sprays. If 4 are needed, you probably started too late. Count the months – we have soybeans in the field from May to September or June to October for the majority of acres. Flowering occurs around July – one spray of stobulurin, triazole or a mixture will last 21 days – then you are into August – then you hit the preharvest window or are into the later growth stages where the crop is mature. It’s time to put the spray truck away. We will be working on a number of spray scenarios, and comparing efficacy as well as economics for many of these this next season. If there is no rust – this information will still provide some important baseline information.

The persistent question – will we see rust in 2005? Depends on how good a winter we have and by good – how many wool sweaters, parkas and fur coats will be needed in Florida. That will be our answer and until March there are other things to focus on.

There has been some rapid movement over the past few weeks by my colleagues at both USDA and Universities. A spore movement prediction system is in place – but still needs some ground sampling, it is highly likely that we will have monitoring plots throughout the US as well as in Ohio. June is our target to really begin intensively scouting for this disease – if it has been found in the southern US. Fungicide guidelines will be in place. Companies are ramping up and supplies will be strategically placed in the US.

What can you do? As I’ve said before – take care of immediate business; choose the best varieties, with the best disease resistance packages for your farm. Look for ways optimize your inputs – so if you do need to make an investment in spraying you will have the financial room.

We will feature Soybean Rust at the http://www.oardc.ohio-state.edu/cropprofit/ satellite conference on February 15, 2005 at your local county extension office. Continuous updates will be posted to the C.O.R.N. Newsletter as we learn things.

Canopy XL becomes Canopy EX – OK with U?

Authors: Mark Loux

All right - so it’s a stupid title for an article. We have received many questions about the replacement of Canopy XL with Canopy EX. Some discussion of the evolution of Canopy formulations is probably merited here, since it helps provide some perspective on how Canopy EX stacks up against other broad-spectrum products such as Gangster.

DuPont initially sold the product Preview, which was a premix of chlorimuron (Classic) plus metribuzin (Sencor) for preplant or preemergence application to soybeans. This later evolved to Canopy and Canopy SP, which contained a lower rate of metribuzin compared to Preview. Preplant application of chlorimuron alone actually provides adequate residual control of a number of broadleaf weeds, including lambsquarters, pigweeds, smartweeds, velvetleaf, marestail and common ragweed, and it controls or suppresses giant ragweed, morningglory, and cocklebur. The addition of metribuzin to chlorimuron resulted in greater burndown activity in no-till, and at least some residual control of annual grasses and ALS-resistant common ragweed, pigweeds, and marestail, depending upon the product and rate applied. Preview and Canopy products tended to have a good fit in Ohio no-till soybean production, due to their combination of burndown activity and broad-spectrum residual broadleaf control. However, the premixes of metribuzin plus chlorimuron were phased out, and replaced with Canopy XL, a premix of chlorimuron plus sulfentrazone (Authority). This substitution resulted in an overall reduction in the burndown activity, since sulfentrazone has little foliar activity on many emerged weeds (with few exceptions where activity improved, star-of-Bethlehem and purple deadnettle). However, sulfentrazone provided residual control of black nightshade, which chlorimuron and metribuzin do not control, along with ALS-resistant waterhemp and marestail.

Dupont is no longer producing Canopy XL, and has replaced it with Canopy EX, which is already being sold for use in fall herbicide applications. Canopy EX is a premix of chlorimuron plus tribenuron (Express). Express has foliar activity on common chickweed and a number of other winter annual weeds, and has typically been added to fall Canopy treatments to control chickweed. Express is short-lived in soil and provides essentially no residual weed control. While Canopy XL and EX are comparable for control of most annual broadleaf weeds, there are some differences:

- Canopy EX may have somewhat better activity on emerged weeds than Canopy XL, and specifically on winter annuals and dandelion. Canopy EX controls common chickweed, whereas Canopy XL did not. However, Canopy EX will not control star-of-Bethlehem, whereas Canopy XL did.
- Canopy EX will not provide residual control of black nightshade, waterhemp, or ALS-resistant marestail, whereas Canopy XL did control these weeds. Canopy XL was capable of suppressing annual grasses for several weeks after application, and this is much less likely with Canopy EX.
- Whereas Canopy XL could occasionally cause minor stunting of soybeans, the Express component of Canopy EX can be more injurious to soybeans if applied at the time of soybean planting. The current Canopy EX label specifies 45 days between application and soybean planting, although this should be shortened to 7 days sometime in the future.

The 45-day interval between application and soybean planting greatly reduces the utility of Canopy EX in spring herbicide programs, since it would have to be applied by mid-March to accommodate an early-May soybean planting. Those producers looking for a product that provides broad-spectrum control similar to Canopy EX, with more flexibility in the window of application, should consider Gangster. Gangster is a co-pack of FirstRate plus Valor, and this mixture is actually more effective than Canopy EX for residual control of black nightshade, waterhemp, and ALS-resistant ragweed and marestail. Residual control of other broadleaf weeds should be similar between the two products, and Valor can suppress annual grasses for several weeks after application. We consider the burndown activity of Canopy EX to be more effective than Gangster, with the exception of star-of-Bethlehem. Chlorimuron has been especially helpful for control of emerged dandelion when combined with glyphosate or glyphosate plus 2,4-D. The Valor component of Gangster provides more rapid burndown of dandelions, but chlorimuron is more helpful in final control and reduction in populations. However, Gangster is probably still the best choice as a replacement for Canopy EX as long as the latter cannot be applied within 45 days of soybean planting.

Crop Production Conference and OSU Advanced Agronomy Workshop

Authors: Mark Loux

The OABA/OSU Crop Production Conference will be held on January 12, 2005 at the OSU Fawcett Center in Columbus. Topics on the program include: nitrogen management, glyphosate stewardship, soybean rust, drainage management, and annual updates from OSU Extension specialists, among others. The program is pre-approved for 5 CCA CEU’s and 3 hours of pesticide recertification credit. On the following day, January 13, OSU will conduct an Advanced Agronomy Workshop at the Fawcett Center, which will provide 8 hours of CCA CEU’s (2 in each CCA category). This workshop is designed to provide in-depth information in a number of areas, including: soil organic matter; the effect of soil type on crop growth; seed quality assessment; and fungicide site of action and resistance, among others. Hands-on sessions on weed and insect identification and the effect of stress during ear development on corn grain yield will also be conducted. Cost of the programs through advance registration: $70 for the Crop Production Conference and $100 for the Advanced Agronomy Workshop, which includes breaks and lunch. For more information or to register, contact the Ohio Agribusiness Association at 614-326-7520, or visit their website, http://www.oaba.net/ (registration via the web should be available later this week).

Crop Profit Game Satellite Conference

Authors: Greg LaBarge

The first of three Crop Profit Game broadcast will be December 14th from 7-9 pm. These programs will build upon each other in sharing the latest on research information, recommendations and input concerns for Ohio row crop producers. Broadcast will be available at many Extension Offices across the state. For the location nearest to you call your local extension office or see http://www.oardc.ohio-state.edu/cropprofit/ for an interactive map or zip code search.

Many counties have added additional local programs for pesticide recertification and updates. Be sure to check for beginning times and locations.

Also mark your calendars for the other Crop Profit Game dates January 11th and February 15th. Agenda’s for these upcoming programs can be found at http://www.oardc.ohio-state.edu/cropprofit/. If you have question about these programs contact Greg La Barge at 419-337-9210 or labarge.1@osu.edu or Harold Watters at 937-440-3945 or watters.35@osu.edu.

Archive Issue Contributors: 

State Specialists: Pat Lipps and Anne Dorrance (Plant Pathology), Robert Mullen (Soil Fertility), Mark Loux and Jeff Stachler (Weed Science), Ron Hammond (Entomology) and Ed lentz (Agronomy). Extension Agents and Associates: Glen Arnold (Putnam), Roger Bender (Shelby), Greg Labarge (Fulton), Gary Wilson (Hancock), Dusty Sonnenberg (Henry) and Harold Watters (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.