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How To Interpret Scn Soil Test Results, Gregory L. Tylka Dec 2006

How To Interpret Scn Soil Test Results, Gregory L. Tylka

Integrated Crop Management News

Soybean yield loss due to the soybean cyst nematode (SCN) occurred throughout much of Iowa in 2006. Damage from this pest was particularly noticeable in areas of the state that were very dry. There seems to be increased interest in testing for and managing SCN in Iowa this fall, and there likely has been more fields sampled for SCN this fall than in recent years. Following are some commonly asked questions and answers that illustrate things to consider when interpreting SCN soil sample results. This information is excerpted from Iowa State University Extension publication IPM 61, Interpreting SCN Soil Sample ...


Scn-Resistant Soybean Varieties For 2007: Many Choices, Few Sources Of Resistance, Gregory L. Tylka Nov 2006

Scn-Resistant Soybean Varieties For 2007: Many Choices, Few Sources Of Resistance, Gregory L. Tylka

Integrated Crop Management News

The soybean cyst nematode (SCN) is a major yield-limiting pest of soybeans throughout the Midwest that can be managed very effectively through use of SCN-resistant soybean varieties. Resistant varieties reduce the amount of SCN reproduction (and population density buildup) that occurs while producing significantly greater soybean yields than non-resistant (susceptible) varieties in fields infested with the nematode. The Iowa State University Extension publication titled Soybean cyst nematode-resistant soybean varieties for Iowa has recently been updated, is now available, and lists SCN-resistant soybean varieties available to Iowa growers in late maturity group 0 and maturity groups 1, 2, and 3.


Late Movement Of Soybean Rust, Daren S. Mueller Nov 2006

Late Movement Of Soybean Rust, Daren S. Mueller

Integrated Crop Management News

After a hot, dry summer with very little movement, soybean rust made a late push both up the East Coast and into the Ohio River Valley. After the dust settled from the excitement in October, rust was reported in 159 new counties, including seven new states (Arkansas, Illinois, Indiana, Kentucky, Missouri, Tennessee, and Virginia). Soybean rust season totals to date are 230 counties in 15 states on soybean and 262 counties total (including kudzu). Last year at this time, there were only 130 counties in seven states positive for soybean rust. No rust was found in Iowa despite extensive scouting ...


What's Your Type?: An Hg Type Test For Scn Populations, Gregory L. Tylka Nov 2006

What's Your Type?: An Hg Type Test For Scn Populations, Gregory L. Tylka

Integrated Crop Management News

SCN-resistant soybean varieties reduce the amount of SCN reproduction that occurs when soybeans are grown. But if resistant soybean varieties are grown repeatedly, an SCN population capable of reproducing readily on the resistant varieties can develop. This is because resistant varieties are not immune; they allow some low level of SCN reproduction. The possibility of SCN populations building up on resistant varieties is especially a concern because almost all resistant soybean varieties have SCN resistance genes from the soybean breeding line PI88788 (see article on newly published list of SCN-resistant soybean varieties for 2007 in this issue).


Check Fields For Scn To Prepare For 2007, Gregory L. Tylka Oct 2006

Check Fields For Scn To Prepare For 2007, Gregory L. Tylka

Integrated Crop Management News

The soybean cyst nematode (SCN) continues to be an extremely damaging and widespread pest of soybean in Iowa and many other Midwestern states. The nematode infests more than 70 percent of the fields in Iowa and more than 80 percent of the fields in Illinois. Often there is no obvious stunting or yellowing of soybean plants in infested fields. Consequently, many SCN-infested fields in Iowa have not been diagnosed.


Two Nematode Soil Sample Analysis Options, Gregory L. Tylka Sep 2006

Two Nematode Soil Sample Analysis Options, Gregory L. Tylka

Integrated Crop Management News

The Iowa State University Plant Disease Clinic offers two different nematode analyses for soil samples--the complete nematode count and the soybean cyst nematode (SCN) egg count. Following is a description of how the two analyses differ and when each analysis should be requested. A complete nematode count gives a count of the worm stages of plant-parasitic nematodes in a soil sample. This analysis does not give a count of the SCN eggs that may be contained in the sample.


Sentinel Plots At End Of The 2006 Season, Ralph Von Qualen, X. B. Yang Sep 2006

Sentinel Plots At End Of The 2006 Season, Ralph Von Qualen, X. B. Yang

Integrated Crop Management News

We are completing our second crop season since Asian soybean rust (ASR) was found in the United States. We can breathe a sigh of relief and give thanks that ASR did not make its way to Iowa. Indeed, this potentially devastating disease has not plagued the entire north-central United States. Had conditions been favorable for this disease, we were ready to give producers fair warning.


A Step Toward Control Of Bean Pod Mottle Virus: Identifying Field Tolerance, John H. Hill, Craig Grau Sep 2006

A Step Toward Control Of Bean Pod Mottle Virus: Identifying Field Tolerance, John H. Hill, Craig Grau

Integrated Crop Management News

So, have you been wondering what to do about all those soybean plants that have mottled leaves? Populations of bean leaf beetles, the insect that efficiently transmits bean pod mottle virus, have been very high. The last issue of the ICM newsletter told you to expect potential yield reductions this fall and reduced seed quality evidenced by seeds that are stained (hilum bleeding). But there may be some soybean cultivars/accessions that are not so bad. We have known for some time that soybean cultivars can vary significantly in response to disease caused by the virus.


Soybean Cyst Nematode May Cause Soybeans To Mature Early, Gregory L. Tylka Sep 2006

Soybean Cyst Nematode May Cause Soybeans To Mature Early, Gregory L. Tylka

Integrated Crop Management News

Soybean cyst nematode (SCN) is a widespread and serious pest of soybeans in Iowa. But the nematode often does not cause obvious above-ground symptoms, at least not until population densities become extremely high. One fairly consistent, albeit somewhat indirect, symptom of SCN parasitism that is apparent at this time of the year is early senescence of the soybeans. The early senescence of soybean caused by SCN is illustrated in the diagram on page 227. The squares in the map in the diagram represent 3-foot by 3-foot (9 ft2) square areas of the field. Three 1-inch diameter, 8-inch deep soil cores ...


Bean Pod Mottle Virus: Back With A Vengeance, John H. Hill, Palle Pedersen, Jeffrey D. Bradshaw Aug 2006

Bean Pod Mottle Virus: Back With A Vengeance, John H. Hill, Palle Pedersen, Jeffrey D. Bradshaw

Integrated Crop Management News

As stated in an earlier article in the ICM Newsletter (May 15, 2006), bean leaf beetles are back with a vengeance this year. Based on observations from agronomists across the state, this year seems to have the highest level of bean leaf beetles since 2002. This also has resulted in an apparent high incidence of bean pod mottle virus disease in Iowa fields. Infected plants can be characterized by the leaves, which show a yellow to green blotchy appearance called leaf mottle. Sometimes leaves have a raised or blistered appearance.


Update: Soybean Rust And Other Foliar Diseases, Daren S. Mueller Aug 2006

Update: Soybean Rust And Other Foliar Diseases, Daren S. Mueller

Integrated Crop Management News

Another growing season is passing and soybean rust remains confined to the southeastern United States. With drier-than-normal conditions throughout much of the southeastern United States early in the spring and well into summer, soybean rust has not been able to spread too far from the overwintering sites. To date for 2006, there are 28 counties in six states with soybean rust. In comparison to 2005, there were 21 counties with soybean rust in early August (see maps).


Recent Soybean Yellowing May Be Symptom Of Scn, Gregory L. Tylka Jul 2006

Recent Soybean Yellowing May Be Symptom Of Scn, Gregory L. Tylka

Integrated Crop Management News

There have been many yellow spots in soybean fields throughout Iowa so far this season. In most cases, the yellowing is iron deficiency chlorosis. But since mid-July, additional yellowing of soybean fields has appeared, and it is likely that at least some of the newly appearing chlorosis is being caused by feeding of the soybean cyst nematode (SCN). SCN usually is present in fields for many years before population densities increase to a level that causes obvious stunting or yellowing.


Consider Nematode Feeding As Cause For Poor Corn Growth, Gregory L. Tylka Jul 2006

Consider Nematode Feeding As Cause For Poor Corn Growth, Gregory L. Tylka

Integrated Crop Management News

Plant-parasitic nematodes can cause serious damage to corn. There are numerous species that occur in Iowa, including those with common names like the dagger, lance, lesion, needle, spiral, stubby-root, and stunt nematodes. Symptoms of nematode damage on corn include stunting and/or yellowing of foliage, uneven tasseling, and stunting, swelling, and/or browning of roots.


Midsummer Soybean Disease Scouting, X. B. Yang Jul 2006

Midsummer Soybean Disease Scouting, X. B. Yang

Integrated Crop Management News

Cool weather this year has resulted in different soybean diseases than we have experienced in other years. Cool and wet conditions are favorable to the development of fungal disease. This year has been cool but not wet; therefore, the disease picture will be unique. This article discusses diseases that you are likely to find during summer disease scouting.


Fungicides: Safety And Restrictions, Daren S. Mueller, Joyce Hornstein Jul 2006

Fungicides: Safety And Restrictions, Daren S. Mueller, Joyce Hornstein

Integrated Crop Management News

Reading through a pesticide label will give you most of the needed information concerning safety for both yourself and others while spraying field crops. Below is a synopsis of some of the dangers and restrictions for some common fungicides. For details on a specific fungicide, please follow the label's directions for mixing and application along with the instructions for safe use.


Assessing The Risk Of Soybean White Mold In 2006, X. B. Yang Jul 2006

Assessing The Risk Of Soybean White Mold In 2006, X. B. Yang

Integrated Crop Management News

Soybean white mold was prevalent during the 2004 season in eastern Iowa. Many of the infested fields were replanted with soybean this year. Some farmers, especially those in eastern Iowa, have questioned the risk of soybean white mold this year. White mold management measures are preventative and include the application of chemicals. This means that correctly assessing the risk of this disease helps guide our decisions on chemical controls. This article discusses the risk factors to help you assess the risk for this season.


Fungicides: Plant Health Fungicide Applications, Daren S. Mueller Jun 2006

Fungicides: Plant Health Fungicide Applications, Daren S. Mueller

Integrated Crop Management News

If you take a look at the current distribution of soybean rust in the United States and listen carefully to the experts on the chances of rust making it to Iowa, you have to be encouraged. Despite the good news about soybean rust not spreading quickly (or hardly at all), there have been several reports of chemical reps from major fungicide manufacturers trying to convince growers to purchase fungicides and apply them to soybean to enhance plant health, leading to higher crop yields; suggested treatments involve QoI-containing fungicides, such as Headline® or Quadris®.


Fungicides: Why Fungicides Fail, Daren S. Mueller Jun 2006

Fungicides: Why Fungicides Fail, Daren S. Mueller

Integrated Crop Management News

Sometimes management of plant diseases is accomplished through the application of fungicides. Many factors prior to, during, and after application will determine the success of the fungicide. On certain occasions, fungicide applications fail to manage the targeted disease. It is important to identify the reasons for these failures to prevent them from occurring in the future.


Soybean Cyst Nematode Females Now Apparent On Roots, Gregory L. Tylka Jun 2006

Soybean Cyst Nematode Females Now Apparent On Roots, Gregory L. Tylka

Integrated Crop Management News

The soybean cyst nematode (SCN), Heterodera glycines, is a widespread, destructive pest of soybeans in Iowa and much of the Midwest. Fortunately, SCN can be managed successfully by growing nonhost crops, such as corn, and resistant soybean varieties. But plants in many infested fields may not be stunted and yellow, at least not until SCN population densities (numbers) develop to high levels. It may take several years before noticeable symptoms of SCN damage become apparent.


Spore Traps Help Researchers Watch For Soybean Rust, Ralph Von Qualen, X. B. Yang Jun 2006

Spore Traps Help Researchers Watch For Soybean Rust, Ralph Von Qualen, X. B. Yang

Integrated Crop Management News

We want to keep track of any movement of soybean rust so that we can inform and warn Iowa producers of any risk to their crop. Last year a spore tracking system was set up in the southern states as a part of soybean rust monitoring efforts. In some locations, spores were detected with the spore traps and the spore maps were generally consistent with the predicted spore map, according to reports presented last winter. In the North Central Region, spores also were detected with another type of spore trap.


Fungicides: Fungicide Resistance And The Frac Code, Daren S. Mueller Jun 2006

Fungicides: Fungicide Resistance And The Frac Code, Daren S. Mueller

Integrated Crop Management News

Fungicides that may become an integral part of soybean production are already used in corn and small grain production under certain situations. Since fungal pathogens are often highly variable and may be able to adapt to repeated fungicide sprays, resistance management may become an issue. It is important to protect effective groups of fungicides because resistance may lead to unexpected and costly crop losses to growers, and loss of a valuable product.


Fungicides: Others, Daren S. Mueller Jun 2006

Fungicides: Others, Daren S. Mueller

Integrated Crop Management News

Other fungicides available for use on field crops in Iowa are in the benzimidazoles class or are contact fungicides. Benzimidazoles are widely used fungicides that first became available in the late 1960s; however, thiophanate-methyl is the only fungicide in this class labeled for use on field crops in Iowa. Benomyl also is in this fungicide class but is no longer commercially available. Benzimidazoles are effective against a broad range of fungi that cause leaf spots, root and crown rots, stem rots, and powdery mildew--but not rusts.


Fungicides: Triazoles, Daren S. Mueller May 2006

Fungicides: Triazoles, Daren S. Mueller

Integrated Crop Management News

The fungicide group, demethylation inhibitors (DMI), which contain the triazole fungicides, was introduced in the mid-1970s. Triazoles consist of numerous members, of which several are labeled or are in the process of being labeled for use on field crops in Iowa--cyproconazole, flusilazole, flutriafol, metconazole, myclobutanil, propiconazole, prothioconazole, tebuconazole, and tetraconazole.


Soybean Rust Update And Outlook, X. B. Yang, Paul Esker, Xun Li, Zaitao Pan, Lulin Xue May 2006

Soybean Rust Update And Outlook, X. B. Yang, Paul Esker, Xun Li, Zaitao Pan, Lulin Xue

Integrated Crop Management News

Soybean planting and germination are well under way in Iowa. Similar to our work last year, we have been using computer modeling results combined with information from sentinel plot data to project the seasonal progress of soybean rust and the potential risk for Iowa. Below is our update and seasonal outlook.


Corn Seedling Health And Stand Establishment, Alison E. Robertson May 2006

Corn Seedling Health And Stand Establishment, Alison E. Robertson

Integrated Crop Management News

With all of the corn planted and most of the soybean, now is the time to start evaluating plant stands. Corn germination and emergence were prolonged by cooler than normal temperatures that occurred during planting. Cool soil conditions (<50–55 °F) also predispose seedlings to infection by a number of fungi that cause seedling disease, and can result in seedling death. Therefore, as you start to assess plant stands, it is important to dig up seedlings every now and then to check general root health. Uneven emergence and stunted seedlings may indicate seedling disease but also can be due to insect feeding and herbicide damage.


Fungicides: Qoi Fungicides, Daren S. Mueller May 2006

Fungicides: Qoi Fungicides, Daren S. Mueller

Integrated Crop Management News

Quinone outside inhibitor (QoI) fungicides include three fungicide families, the well-known family of strobilurins and two new families, represented by fenamidone and famoxadone. QoI fungicides approved for, or in review for, use on field crops in Iowa include strobilurins azoxystrobin, pyraclostrobin and trifloxystrobin, and famoxadone. These fungicides are used on cereal grains, corn, and soybean as well as many other crops in Iowa, such as fruit trees, small fruit, vegetables, and turf.


Fungicides: Terminology, Daren S. Mueller May 2006

Fungicides: Terminology, Daren S. Mueller

Integrated Crop Management News

Many growers have never used foliar-applied fungicide for management of field crop diseases, especially on soybean. At this time, foliar-applied fungicides are the only effective option for managing Asian soybean rust. In the following weeks, there will be a series of articles to help producers understand fungicides and how they affect their production practices. Some of the commonly used terms are defined below:


Alto 100sl Approved For Soybean Rust, Daren S. Mueller, Chuck Eckermann May 2006

Alto 100sl Approved For Soybean Rust, Daren S. Mueller, Chuck Eckermann

Integrated Crop Management News

The fungicide Alto 100SL (cyproconazole), manufactured by Syngenta Crop Protection, Inc., has been approved as a Section 18 fungicide in Iowa, effective on April 19, 2006. The exemption will expire on April 19, 2009. Alto 100SL is a systemic, triazole fungicide with early infection and protectant activity. It has post-infection activity that can stop pathogen establishment in the early phases of disease development. Alto 100SL also can stop sporulation, reduce inoculum production, and slow disease progress.


Iowa Soybean Rust Sentinel Plots, Ralph Von Qualen, X. B. Yang Apr 2006

Iowa Soybean Rust Sentinel Plots, Ralph Von Qualen, X. B. Yang

Integrated Crop Management News

Iowa's sentinel plots are being planted so that we can monitor any development of soybean rust during 2006. During this growing season, sentinel plots are being established in 21 locations in Iowa (see map below) as part of coordinated national efforts funded by check-off dollars and federal funds. Most plots are located at Iowa State University research farms, where the rust will be monitored and scouted closely. Our cooperators are planting Iowa's sentinel plots early so they will be at a reproductive growth stage sooner.


Look Out For An Early Season Corn Nematode Problem, Gregory L. Tylka Apr 2006

Look Out For An Early Season Corn Nematode Problem, Gregory L. Tylka

Integrated Crop Management News

Generally, plant-parasitic nematodes are discussed as a problem on corn in July and August because that usually is the time when their damage becomes apparent and also when soil samples should be collected for diagnosis. But there is an exception to this generalization--the needle nematode. The needle nematode has been found in several fields in southeastern Iowa in past growing seasons, and this nematode is unusual in many regards.