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Knowing The Risk Of Soybean Rust By Comparison With Brazil, X. B. Yang, Emerson M. Del Ponte, Ana Paula Dias Dec 2004

Knowing The Risk Of Soybean Rust By Comparison With Brazil, X. B. Yang, Emerson M. Del Ponte, Ana Paula Dias

Integrated Crop Management News

One of the common questions we receive is whether to move away from soybean because of the risk of soybean rust (SBR). Although studies indicate that the U.S. soybean production region is suitable to this disease, many experts believe outbreaks of the disease are likely to be sporadic.


Scn-Resistant Soybean Varieties Listed In Updated Publication, Gregory L. Tylka Nov 2004

Scn-Resistant Soybean Varieties Listed In Updated Publication, Gregory L. Tylka

Integrated Crop Management News

Soybean cyst nematode (SCN) is a serious and widespread pest of soybean throughout Iowa and the Midwest. Fortunately, SCN-resistant soybean varieties have been developed and are an effective management tool. To assist growers in choosing SCN-resistant varieties, Iowa State University Extension annually compiles and publishes a list of public and private SCN-resistant soybean varieties in maturity groups I, II, and III.


Soybean Rust First Detector Training Session Announced, Gregory L. Tylka, Brent A. Pringnitz Nov 2004

Soybean Rust First Detector Training Session Announced, Gregory L. Tylka, Brent A. Pringnitz

Integrated Crop Management News

Asian soybean rust is a topic of great interest among Iowa soybean growers and agribusiness. The Iowa Department of Agriculture and Land Stewardship, the Iowa Soybean Association and Promotion Board, and Iowa State University have formed the Iowa Soybean Rust Team and have developed a system in Iowa whereby soybean samples that are suspected of possibly being infected with soybean rust can be examined and passed through a sequence of trained personnel to offer Iowa soybean growers rapid and accurate identification of the disease.


Asian Soybean Rust Confirmed In The Continental United States, Alison E. Robertson Nov 2004

Asian Soybean Rust Confirmed In The Continental United States, Alison E. Robertson

Integrated Crop Management News

On November 10, 2004, the United States Department of Agriculture (USDA) and the Iowa Department of Agriculture and Land Stewardship announced that Asian soybean rust has been confirmed near Baton Rouge, LA. The fields where the rust was found are located on research farms belonging to Louisiana State University. No information was given on the stage of plant growth in the fields. Most of the commercial fields in Louisiana have been harvested. X.B. Yang, Iowa State University plant pathologist, is one of the leading experts in the world and has flown down to Louisiana as a member of the ...


Corn Ear Molds And Mycotoxins In Fall 2003, Gary P. Munkvold Oct 2004

Corn Ear Molds And Mycotoxins In Fall 2003, Gary P. Munkvold

Integrated Crop Management News

There has been elevated concern again this year about mycotoxins in grain, especially aflatoxins. Aflatoxins are not a common problem in Iowa, but the dry weather that occurred in some parts of the state caused stress on the plants, which lead to aflatoxin problems. Corn plants that experience drought stress are more susceptible than usual to the fungus that produces aflatoxins, Aspergillus flavus.


Check Seed Quality At Harvest, X. B. Yang Oct 2004

Check Seed Quality At Harvest, X. B. Yang

Integrated Crop Management News

This growing season, diseases caused by Cercospora fungi were widespread in Iowa. There were twoCercospora species, one causing frogeye leaf spot and another causing Cercospora leaf blight. Frogeye leaf spot occurred locally in southern Iowa and Cercospora leaf blight was widely spread throughout Iowa. In some cases, Cercospora leaf blight has been called "sunburn." Because fungi of both diseases can infect seeds at harvest, it is likely that soybean from some fields show seed discoloration, which happened two years ago in northern Iowa. This article addresses the seed quality issue of this fall.


Stinkhorns Spotted In Fields, Paula Flynn Oct 2004

Stinkhorns Spotted In Fields, Paula Flynn

Integrated Crop Management News

John Holmes, extension field crop specialist, reported that farmers are finding lots of stinkhorn mushrooms in soybean fields as they harvest. These fungi do not cause disease to plants or animals, but instead live a harmless existence on dead organic matter such as crop debris. They also are commonly found on decaying mulch. A stinkhorn begins life as an egg-like structure.


Fall Is Prime Time To Sample Fields For Scn, Gregory L. Tylka Oct 2004

Fall Is Prime Time To Sample Fields For Scn, Gregory L. Tylka

Integrated Crop Management News

The soybean cyst nematode (SCN) is an extremely damaging and widespread pest of soybean in Iowa. The nematode infests approximately 70 percent of the fields statewide. However, SCN usually causes no obvious aboveground symptoms for many years after being introduced into a field. Consequently, many SCN-infested fields in Iowa have not been diagnosed. The lack of symptoms and subsequent missed diagnosis are unfortunate because the key to effective management of SCN is early detection, before large nematode population densities develop.


Corn Ear Rots, Alison E. Robertson Oct 2004

Corn Ear Rots, Alison E. Robertson

Integrated Crop Management News

This year does not appear to be a particularly bad year for ear rots. The season has been cooler than normal, and the weather has been fairly dry since silking. However, some field crop specialists have noticed ear rot problems, in particular, Diplodia ear rot. The incidence of corn ear rot should be determined before harvest for a number of reasons. First, ear rot diseases can reduce yield and quality of the corn harvest. Second, some of the fungi that infect corn ears may produce mycotoxins, which are harmful, and can be fatal, to livestock. Finally, ear rots can continue ...


Check Seed Quality At Harvest, X. B. Yang Oct 2004

Check Seed Quality At Harvest, X. B. Yang

Integrated Crop Management News

This growing season, diseases caused by Cercospora fungi were widespread in Iowa. There were twoCercospora species, one causing frogeye leaf spot and another causing Cercospora leaf blight. Frogeye leaf spot occurred locally in southern Iowa and Cercospora leaf blight was widely spread throughout Iowa. In some cases, Cercospora leaf blight has been called "sunburn." Because fungi of both diseases can infect seeds at harvest, it is likely that soybean from some fields show seed discoloration, which happened two years ago in northern Iowa. This article addresses the seed quality issue of this fall.


Remember To Scout For Corn Stalk Rots, Alison E. Robertson Sep 2004

Remember To Scout For Corn Stalk Rots, Alison E. Robertson

Integrated Crop Management News

Stalk rot occurs to some extent in every cornfield in Iowa each year because as corn stalks mature, they naturally decay. However, stalk rot can occur prior to physiological maturity and is considered a disease problem, which reduces yields in two ways. First, affected plants die prematurely (Fig. 1) and therefore produce lightweight ears with poorly filled kernels. Second, and this is more common, plants with stalk rot easily lodge (Fig. 2), which makes harvesting difficult, and many ears are left in the field.


Note For Fall Soybean Diseases, X. B. Yang, Shrishail S. Navi Sep 2004

Note For Fall Soybean Diseases, X. B. Yang, Shrishail S. Navi

Integrated Crop Management News

It is well established that outbreaks of plant diseases are associated with extreme weather. This year's extreme weather created favorable conditions for several soybean diseases. Sudden death syndrome(SDS) was severe in southern Iowa, and severe outbreaks of white mold occurred in eastern Iowa. The two diseases also occurred in other parts of Iowa, and an article will address the management of the two diseases later this year. Besides these two diseases, several other diseases are prevalent in fall causing early defoliation, such as brown spot, Cercospora leaf blight, and brown stem rot. In this article, we will discuss ...


Note For Fall Soybean Diseases, X. B. Yang, Shrishail S. Navi Sep 2004

Note For Fall Soybean Diseases, X. B. Yang, Shrishail S. Navi

Integrated Crop Management News

It is well established that outbreaks of plant diseases are associated with extreme weather. This year's extreme weather created favorable conditions for several soybean diseases. Sudden death syndrome(SDS) was severe in southern Iowa, and severe outbreaks of white mold occurred in eastern Iowa. The two diseases also occurred in other parts of Iowa, and an article will address the management of the two diseases later this year.


Diseases Show Up Earlier In 2004, X. B. Yang Aug 2004

Diseases Show Up Earlier In 2004, X. B. Yang

Integrated Crop Management News

Since the third week of July, a few diseases (white mold, sudden death syndrome, and downy mildew) started to show up in Iowa soybean fields. These diseases normally aren't seen until early August. This season's cool weather has promoted their unusually early occurrence.


Soybean Cercospora Diseases Show Up, X. B. Yang Jul 2004

Soybean Cercospora Diseases Show Up, X. B. Yang

Integrated Crop Management News

Since the planting season, weather in Iowa has been cooler and wetter than normal with frequent rainfall. The unusual weather has resulted in the prevalence of foliar diseases. Several diseases have shown up earlier than usual this season. Two weeks ago, we reported that bacterial blight and brown spot were prevalent in Iowa soybean fields. In our early planted research plots, soybean sudden death syndrome started to show foliar symptoms in the second week of July, more than two weeks earlier than normal.


Soybean Diseases To Scout In July, X. B. Yang Jul 2004

Soybean Diseases To Scout In July, X. B. Yang

Integrated Crop Management News

Frequent rain and cool temperatures this crop season have created disease-favorable conditions, resulting in the occurrence of several soybean diseases. Some of the diseases are likely to continue to develop in July. This article summarizes the early-season disease problems encountered thus far and provides some answers to commonly asked questions.


Damping-Off Prevalent This Spring, X. B. Yang Jul 2004

Damping-Off Prevalent This Spring, X. B. Yang

Integrated Crop Management News

The combination of early planting and abundant rains means soybean seedlings have been in cool and wet soil longer than normal this season. That combination creates the perfect breeding ground for soybean seedling diseases. In this Monday's teleconference, almost all Iowa State University Extension field crop specialists (FCS) reported occurrence of damping-off in their regions. Similar reports were received from agronomists from private companies. Replanting resulting from damping-off and other weather related soybean stand reductions has been reported by FCS varying in a range of 2 to 5 percent. Damping-off in corn is also reported.


Soybean Diseases To Scout In July, X. B. Yang Jul 2004

Soybean Diseases To Scout In July, X. B. Yang

Integrated Crop Management News

Frequent rain and cool temperatures this crop season have created disease-favorable conditions, resulting in the occurrence of several soybean diseases. Some of the diseases are likely to continue to develop in July. This article summarizes the early-season disease problems encountered thus far and provides some answers to commonly asked questions.


Holcus Leaf Spot Being Found On Corn, Alison E. Robertson Jul 2004

Holcus Leaf Spot Being Found On Corn, Alison E. Robertson

Integrated Crop Management News

In the past week, the Iowa State University Plant Disease Clinic has received corn leaf samples from northwest Iowa with Holcus leaf spot. Holcus leaf spot is caused by the bacterium Pseudomonas syringae. Light tan (sometimes almost white), round, oval spots, which may appear water soaked at the margins or have a light brown border occur on the lower leaves. The spots are initially about 1/4 inch in diameter, but sometimes grow larger and coalesce into irregular spots and streaks of dead tissue.


Damping-Off Prevalent This Spring, X. B. Yang Jun 2004

Damping-Off Prevalent This Spring, X. B. Yang

Integrated Crop Management News

The combination of early planting and abundant rains means soybean seedlings have been in cool and wet soil longer than normal this season. That combination creates the perfect breeding ground for soybean seedling diseases. In this Monday's teleconference, almost all Iowa State University Extension field crop specialists (FCS) reported occurrence of damping-off in their regions. Similar reports were received from agronomists from private companies.


Assessing The Risk Of Soybean Rust For The 2004 Season, X. B. Yang, Shimon Pivonia Jun 2004

Assessing The Risk Of Soybean Rust For The 2004 Season, X. B. Yang, Shimon Pivonia

Integrated Crop Management News

In recent Iowa State University triage training meetings, a most talked about topic is how to assess the risk of soybean rust, specifically (1) whether the disease will show up in the 2004 season in the continental U.S., and (2) what damage potential it will have if the disease arrives this season. We summarized questions from participants and will address some of them.


Wheat Scab Prediction Model Available To Growers, Alison E. Robertson May 2004

Wheat Scab Prediction Model Available To Growers, Alison E. Robertson

Integrated Crop Management News

Wheat in southern Iowa has now headed. Wheat is most susceptible to Fusarium head blight (scab) during flowering growth stages; however, some infection can occur during kernel development. Although scab often is not a problem in Iowa, if weather conditions are wet the disease can threaten wheat crops as it did in 1996.


Stewart's Disease Risk For 2004, Alison E. Robertson, Marlin E. Rice May 2004

Stewart's Disease Risk For 2004, Alison E. Robertson, Marlin E. Rice

Integrated Crop Management News

There have been reports of corn flea beetles in southern Iowa from May 4 to 10. Overwintering flea beetles may be infested with the bacterium Pantoea (Erwinia) stewartii, which causes Stewart's disease. Field corn inbreds and sweet corn are particularly susceptible to this disease. Seed producers should pay attention to early season flea beetle populations because, if left unchecked, you could have substantial Stewart's disease during grain fill, resulting in yield loss.


Soybean Seedling Diseases In 2004, X. B. Yang May 2004

Soybean Seedling Diseases In 2004, X. B. Yang

Integrated Crop Management News

Seedling diseases cause stand reduction in soybean in the spring season, with severity varying from year to year. Once severe stand reduction happens, it is important to determine if a fungal disease is involved before the decision to replant is made. If damping-off is the cause of stand reduction, seed treatment may be needed for replanting. Proper identification of seedling disease is essential for correcting problems in the future. It is also important to know what fungi caused the seedling disease because different fungicides are effective in controlling different fungi.


Soybean Seedling Diseases In 2004, X. B. Yang May 2004

Soybean Seedling Diseases In 2004, X. B. Yang

Integrated Crop Management News

Seedling diseases cause stand reduction in soybean in the spring season, with severity varying from year to year. Once severe stand reduction happens, it is important to determine if a fungal disease is involved before the decision to replant is made. If damping-off is the cause of stand reduction, seed treatment may be needed for replanting. Proper identification of seedling disease is essential for correcting problems in the future. It is also important to know what fungi caused the seedling disease because different fungicides are effective in controlling different fungi.


It's Not Too Late To Sample Fields For Soybean Cyst Nematode, Gregory L. Tylka Apr 2004

It's Not Too Late To Sample Fields For Soybean Cyst Nematode, Gregory L. Tylka

Integrated Crop Management News

There is still time this spring to check fields for the presence of soybean cyst nematode (SCN) before planting starts. This nematode is widespread throughout much of Iowa. However, soybean cyst nemadote infestations can go unnoticed because obvious aboveground symptoms may not be visible for many years after the introduction of the pest into the field. Early detection of soybean cyst nemadote infestations, when population densities (numbers) are still low, is very important. It is much easier to keep low population densities of soybean cyst nemadote in check than to try to decrease high population densities.


Soybean Rust Update, X. B. Yang Mar 2004

Soybean Rust Update, X. B. Yang

Integrated Crop Management News

Soybean rust was one of the major topics of interest and concern among Iowa producers during the winter extension meetings. This article updates the development of soybean rust in the South America and addresses the most commonly asked questions that I received during the extension meetings.


Management Of Charcoal Rot, X. B. Yang, John M. Shriver, Shrishail S. Navi Jan 2004

Management Of Charcoal Rot, X. B. Yang, John M. Shriver, Shrishail S. Navi

Integrated Crop Management News

In the 2003 growing season, charcoal rot caused by a fungus called Macrophomina phaseolina was prevalent in the soybean fields of Iowa, the first ever statewide occurrence. Damage by the disease was not identified by many producers since the disease was relatively new. Surveys covering areas from northern to southern Iowa showed that in the northern Iowa (north of Highway 3), the prevalence was 60 percent. In central Iowa (between Highway 3 and Interstate 80), 90 percent of fields sampled were positive with plants having M. phaseolina. In southern Iowa (south of Interstate 80), 20 percent fields had charcoal rot ...


Population Dynamics Of Corn Flea Beetles And Their Importance For Stewart’S Disease Of Corn, Paul Esker, Forrest W. Nutter Jr. Jan 2004

Population Dynamics Of Corn Flea Beetles And Their Importance For Stewart’S Disease Of Corn, Paul Esker, Forrest W. Nutter Jr.

Iowa State Research Farm Progress Reports

Stewart's disease of corn, caused by the bacterium Pantoea (Erwinia) stewartii, is extremely important for seed and sweet corn producers. Substantial economic losses are possible in both types of production. For the seed corn industry, zero tolerance phytosanitary regulations greatly inhibit the ability of seed corn to be exported from Stewart’s diseaseinfected fields. Management often focuses on the role of the corn flea beetle (Chaetocnema pulicaria) vector that is necessary for both pathogen survival during the winter months and pathogen transmission during the field season. Research on the corn flea beetle is limited, especially in regard to its ...


A Row Cover And Low-Risk Insecticide Strategy For Cucumber Beetle Management, Mark L. Gleason, Sara Jane Helland, Bernard J. Havlovic Jan 2004

A Row Cover And Low-Risk Insecticide Strategy For Cucumber Beetle Management, Mark L. Gleason, Sara Jane Helland, Bernard J. Havlovic

Iowa State Research Farm Progress Reports

Spotted and striped cucumber beetles vector a bacterium that causes wilt in cucurbits. These beetles are the major pest of muskmelons in Iowa. We investigated the success of spun-cotton Reemay row covers and several reduced-risk insecticides for management of cucumber beetles and bacterial wilt.