Welcome to Crop Update for November 14, 2006, published by Sangamon-Menard Extension.

In This Issue

• SO…YOUR STATE HAS SOYBEAN RUST
• PROPHYLACTIC FUNGICIDE USE
• DIPLODIA STALK ROT
• TWO UPCOMING MEETINGS
• SANGAMON-MENARD PRELIMINARY FALL-WINTER MEETING SCHEDULE 2006-2007

SO…YOUR STATE HAS SOYBEAN RUST

Readers are, by now, familiar with the current Asian Soybean Rust (ASR) situation in Illinois. On October 11, soybean trifoliate samples were collected from the Dixon Springs Research Center in southern Illinois because they appeared to have symptoms consistent with Asian Soybean Rust. ASR had just been confirmed in eight Kentucky counties, an ASR spore plume had been projected a few days earlier, and plant pathologists strongly suspected that Illinois would be added to the ASR positive list once soybean fields in the area had been surveyed. The U of I Plant Clinic in Urbana examined the samples, also found them suspect, and shipped those samples to Beltsville, Maryland for final analysis by the Federal government. By October 13, the USDA confirmed that soybean rust had indeed crossed into the state thus marking the first ever Illini rust find. Soybean Rust was found in a total of eight counties – with one of those counties only about 80 miles southeast of the Sangamon County line. The story continued into early November when ASR was found in central Indiana. That Hoosier ASR find was positioned thirty to forty miles north of latitudes associated with Sangamon-Menard communities. What does all this mean for producers in central Illinois? The 2006 advance of ASR into the Midwest means three things.

First, ASR has passed an important psychological barrier that will hopefully ward of complacency in the industry. Let us prove that point by considering recent U.S. soybean rust history. Rust entered the United States for the first time in 2004 but never got close to Illinois that season. Rust spread throughout the southern gulf-states in 2005, and it came within a county of Illinois that fall. Rust has now, again, spread throughout southern gulf-states in 2006 (covering gulf coast regions in particular), it covered much more of Kentucky than it did last year, it spread throughout the soybean region of the Mississippi River valley, it entered the southern part of our state, and it reached central Indiana. Each year, soybean rust has moved progressively closer to central Illinois, and this year it actually entered the Land of Lincoln. This means that Asian Soybean Rust can get here (the agriculture community had begun to doubt that possibility), and that it should again be on the proverbial “radar screen” for Illinois producers. In other words, 2007 will not be the year to “get lazy” about rust vigilance. We have been warned.

Second, the current ASR monitoring system (a series of spore traps and sentinel plots) works very well, and when that system is combined with producer vigilance our ability to reasonably address ASR infestations looks positive. A spore plume was projected and Illinois’ ASR team had enough sentinel plots available in that area to detect the disease. So long as producers remain vigilant, via monitoring some fields weekly during the early season and all fields weekly when rust is “too close for comfort,” and so long as producers monitor the USDA’s Soybean Rust Information site (http://www.sbrusa.net) for late breaking rust news; early detection and management should not be a problem.

Finally, ASR could not have come into Illinois at a better time. Rust is currently a non-issue, no panic about this disease can thus ensue, and we have the whole winter to refresh our memories about this disease while simultaneously fine tuning Illinois’ ASR detection and management system for 2007. Say “thanks” for how rust appeared because the scenario couldn’t have been scripted any better.

PROPHYLACTIC FUNGICIDE USE

Fungicide use has been an increasingly popular topic in the agricultural arena over the last few years. The entry of Asian Soybean Rust into the continental United States provides a partial explanation for this popularity. Producers naturally want to become more familiar with these previously known but rarely used materials just in case rust makes their use a necessity. However, this topic has also become increasingly popular due to reported yield benefits associated with their prophylactic use. In other words, yield benefits have been reported from “blind” applications (i.e. applications made minus a perception of disease severity). Are there benefits from such prophylactic/blind fungicide applications and are there any long term concerns associated with using such pesticides in this way?

Agronomists have confirmed some yield benefits associated with prophylactic fungicide use in soybean fields. As noted by South Dakota State in a multi-state trial, yields did seem to increase approximately 2/3 of the time. However, once cost of production was included, the producer – in that study and similar studies – only made money approximately 1/3 of the time. Additionally, the increase in yield apparently is not directly tied to a specific disease. As noted by Dr. Don Hershman during discussions related to University of Kentucky trials, benefits were apparently derived from increased seed size and weight rather than from decreased disease severity. Hypothesis for this physiologic benefit are many, but none of those possible explanations have been proven. Sangamon-Menard Extension has noted that materials deemed to provide such benefits, members of the Strobilurin fungicide family, kill fungi via halting/decreasing respiration, and we have wondered if that process might partially explain the benefits observed. We have noted that soybeans, a C3 plant, will shift from photosynthesis to photorespiration during hot weather and have openly speculated that such products might decrease the net respiration rate at work within the plant thus allowing it to maintain more sugars thus allowing it to form larger seed. For now, that theory represents speculation, with an abundance of holes, at best. U of I Extension recognizes that such fungicides apparently impact the plant physiologically, thus resulting in some noted yield benefits. However, variable payoffs that only occur about 1/3 of the time in a fairly unpredictable fashion have caused U of I Extension to discourage the practice. Producers can’t afford to gamble resources so we have recommended strip trials, etc. at the most.

The last season did display some exceptional prophylactic fungicide benefits in some area corn fields. At this time, Sangamon-Menard Extension does not believe that such applications resulted in a bean-similar physiologic effect within the plant. Based upon unbelievably intense observations of stalk rot throughout the area, we speculate that fungicide benefits in the corn crop likely were derived via the management of pathogens including Dipoldia, Gibberella, etc. While such diseases will likely present themselves next season at some level, we can not guarantee that disease will occur at economically significant levels and thus can not project secure future benefits from such blind applications of fungicide. We do want to clearly state two words of caution associated with such fungicide use.

First, many of the materials promoted for application in corn fields – as noted earlier – belong to a classification of fungicides termed Strobilurins. Strobilurins, as noted in the University of Illinois’ Report on Plant Diseases 1002, present some real resistance concerns for the plant pathology community. Research has shown that a single letter change in the DNA code is all that is needed for a fungus to develop resistance to Strobilurins. In other words, Strobilurins have a high resistance risk associated with them and excessive use of Strobilurins, minus threshold to trigger and constrain applications, could encourage the development of resistance. Year-in/year-out applications of such products, on a widespread scale, do not bode well for the long term efficacy of these important management tools.

Second, many individuals – at the University level – report a Federal government increasingly dissatisfied with the amount of pesticides used in the Midwest. The Federal government increasingly looks at the money spent on Integrated Pest Management education and sees little to no return on their investment (i.e. little to no evidence of decreased pesticide use and/or little to no evidence of threshold triggered pesticide use). A subtle declaration seems to float about Washington D.C., and that subtle declaration sounds something like this – “If agriculture can not prove itself a better steward of pesticide resources… if agriculture can not better utilize thresholds to only apply such materials when needed, we (The Federal government) will help them improve.” That subtle message, never spoken but ever present just beneath the surface of conversations, should alarm producers. The long range implications of prophylactic pesticide use (not just fungicides) could mean cumbersome government regulations that will increase the cost of production for the American farmer. Sangamon-Menard Extension encourages the agricultural community to use pesticides, including fungicides, wisely lest the impact of insects, weeds, and diseases be accented by government oversight.

DIPLODIA STALK ROT

“Exceptional” – That word best describes the 2006 stalk rot situation in some area corn. Chief among those “rots” was Diplodia. What is it, what causes it, and what can be done to avoid it?

Diplodia stalk rot is an asexual fungal infection caused by Stenocarpella maydis. It overwinters in buried and/or surface proximity stalk debris as small dark brown to black pycnidia (fungal fruiting bodies). The pycnidia are embedded within the rind of the stalk and can thus not be removed when one rubs the stalk with their finger. Given warm, moist conditions spores emerge from those embedded fruiting bodies atop a tiny stalk. Once exposed to the elements, wind and rain transfer those spores about the area, and some of those spores occasionally land on corn plants (the only host plant for this disease). There they penetrate/infect the host, renewing the cycle yet again. Infection typically occurs via crown, mesocotyl, or root infection. Given continuous corn (i.e. a continuous bed for the production of innoculumn) and previously mentioned ideal weather conditions, such infection may progress throughout the lower portion of the plant and/or may appear in ears. Ear infections occur via two pathways. First, spores may be splashed onto silks. The fungus then progresses through the silk directly into the developing ear. Second, spores may be splashed onto husks. The fungus can then – given time and adequate environmental conditions – directly penetrates that tissue gaining access to the developing ear. Producers often note ear rots when they spot a dry, paste-like growth of mycelia on the husk and between/on kernels. The most intense Diplodia infestations may result in light weight kernels that are brown to gray in color. Given enough time and adequate conditions, kernels may take on a gray-black color as embedded pycnidia form on the kernels themselves.

Diplodia stalk rot can be avoided via a combination of management tools. First, crop rotation proves an exceptionally useful tool. Since Stenocarpella maydis survives only on corn tissue, rotation effectively disrupts the lifecycle and will thus stagnate the fungus. Second, burying residue can reduce Diplodia problems as well. Since pycnidia serve as the overwintering stage for this disease and since spores must emerge from these pycnidia, reach the soil surface, and yield spores for further infection to occur, an earthen barrier can prove ideal for physically disrupting this disease. Unfortunately, this successful cultural practice typically proves impractical for most producers. Third, wise hybrid resistance selection is necessary. Gibberella resistance is said to be “strongly correlated” to Diplodia resistance in the literature (Compendium of Corn Diseases – 3rd Edition) and should thus be pursued passionately by the producer.

TWO UPCOMING MEETINGS

December marks the beginning of the 2006-2007 Sangamon-Menard winter meeting season. Those tied to the industry should therefore get a pen and mark the following two programs on their calendar:

– Soil and Water Workshop

Nitrogen management, nutrient transport and water quality will be among the topics discussed at a Soil and Water Management Workshop sponsored by U of I Extension on December 5th. The workshop is offered at the Sangamon-Menard Extension Unit, Illinois State Fairgrounds.

The workshop runs from 9 a.m. to 2:15 p.m. and is presented by an on-site instructor along with teleconference presentations. The program will provide five continuing education units for CCAs.

There is a pre-registration fee of $25 to attend this workshop. The registration fee includes all materials and lunch. To obtain a registration form, contact Sangamon-Menard Extension at 782-4617 (Sprinfield) or 632-7491 (Petersburg).

– Private Applicator Training and Testing

Producers wishing to attend both testing and training for the Private Applicator Test should remember that a $30 fee will be charged.
U of I Extension has previously not required that a fee be included in such training. However, earlier this year U of I Extension decided to include such a fee as part of training and testing clinics across the state. Those planning to attend Private Applicator Training will have to be pre-registered as well.

Should individuals decide to only attend the testing portion, they will not be charged a fee.

Additional fees are administered by the Illinois Department of Agriculture for actual licensing.

Sangamon-Menard Extension’s Private Applicator Training and Testing sessions are December 13 at 1:00 p.m. and January 11 at 6:00 p.m. Those interested in pre-registering for Private Applicator Training and Testing may contact Sangamon-Menard Extension at 217-782-4617.

SANGAMON-MENARD PRELIMINARY FALL-WINTER MEETING SCHEDULE 2006-2007

• December 5 – Soil and Water Workshop
• December 13 – Sangamon-Menard PSEP (Private Applicator Training and Testing) 1:00 PM
• January 3-4 – Illinois Crop Protection Technology Conference
• January 11 – Sangamon-Menard PSEP (Private Applicator Training and Testing) 6:00 PM
• January 12 – Menard County Agronomy Day
• January 16 – Springfield Area Corn and Soybean Classic
• January 29 – Purchasing Healthy Hay—Hay Quality and Selection (Equine Series)
• February 13-14 – Central Illinois Crop Management Workshop
• February 22 – Soil Fertility Workshop
• February 26 – Central Illinois Corn Plant Pathology Workshop
• March 1 – Facilities and Composting for Horse Owners (Equine Series)
• March 12 – Central Illinois Soybean Plant Pathology Workshop

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