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Soybean Seed Coat Mottling, X. B. Yang Jun 1998

Soybean Seed Coat Mottling, X. B. Yang

Integrated Crop Management News

For last week's ICM newsletter, Michael Uphoff and I wrote an article on management of soybean diseases for specialty soybean. In the article we mentioned that soybean mosaic virus (SMV) can cause seed coat discoloration. This week, the ISU extension staff and a seed dealer reported emergence problems of regular soybean seeds that had SMV-like seed coat mottling. This article will address a few questions that should be useful in preventing such problems.


Disease Management For Specialty Soybeans, X. B. Yang, Michael D. Uphoff May 1998

Disease Management For Specialty Soybeans, X. B. Yang, Michael D. Uphoff

Integrated Crop Management News

Production of specialty soybeans, such as tofu soybeans, brings new opportunities for soybean growers. As more and more growers plant specialty soybeans, which are not commonly bred for disease resistance, we have received an increased number of questions on disease management. Common questions can be grouped into two areas: the first pertains to diseases that cause stand reduction and the second relates to seed quality.


Scouting For Soybean Seedling Diseases, X. B. Yang May 1998

Scouting For Soybean Seedling Diseases, X. B. Yang

Integrated Crop Management News

When soybeans start to emerge, a few of us may experience stand reductions caused by seedling diseases. Several fungi can cause stand establishment problems either before or after soybean emergence. Pythium, Phytophthora, Rhizoctonia, and Fusarium are fungi that cause seedling blight in Iowa. Research shows that the first three fungi account for about 90 percent of disease-related stand reduction problems in Iowa. Fusarium is a minor problem. Determining which fungi are the cause of a problem in a particular field is a main task of scouting.


Controlling Wheat Leaf Diseases, Gary P. Munkvold May 1998

Controlling Wheat Leaf Diseases, Gary P. Munkvold

Integrated Crop Management News

Now is the time to start thinking about controlling leaf diseases in wheat if necessary. Conditions have been wet enough in the southern Iowa wheat-producing areas to promote significant leaf disease development. Wheat can be affected by a number of foliar diseases caused by fungi, including Septoria leaf blotch, powdery mildew, and tan spot. There are also three different rust fungi that can infect wheat. Leaf rust, Puccinia recondita, is the most common rust disease and has the most destructive potential of the foliar diseases.


Alfalfa Leaf Diseases Reported, X. B. Yang, Gary P. Munkvold May 1998

Alfalfa Leaf Diseases Reported, X. B. Yang, Gary P. Munkvold

Integrated Crop Management News

Alfalfa is turning green early in this warmer-than-usual spring and the frequent rains have promoted foliar diseases in parts of Iowa. Last week, ISU extension field specialists-crops Brian Lang (northeast) and Virgil Schmitt (east) reported spring black stem, and Mark Carlton (south central) reported Leptosphaerulina leaf spot.


Alfalfa Seedling Diseases In 1998, Gary P. Munkvold Apr 1998

Alfalfa Seedling Diseases In 1998, Gary P. Munkvold

Integrated Crop Management News

Wet conditions have delayed new alfalfa seedings in many parts of the state, and these conditions also may lead to problems with soilborne fungi. Several genera of fungi can attack alfalfa seedlings, includingPhytophthora, Pythium, Aphanomyces, Fusarium, and Rhizoctonia. Traditionally, Phytophthora andPythium have been considered the primary pathogens, but recently Aphanomyces euteiches has been more widely recognized. According to a survey we did in 1994, Aphanomyces is more common thanPhytophthora in Iowa soils, and these two fungi should be considered equal threats to seedlings. Seedling diseases should be suspected when emergence is poor and/or there are obviously ...


Plan Your Disease Scouting, X. B. Yang Apr 1998

Plan Your Disease Scouting, X. B. Yang

Integrated Crop Management News

As crop scouts, we know that detecting a disease in the early stages of its development is critical to disease management. Early detection of a disease can help us make management decisions to minimize disease risk or to prevent disease problems before they take place.


Planting Date And Soybean Diseases, X. B. Yang Apr 1998

Planting Date And Soybean Diseases, X. B. Yang

Integrated Crop Management News

We know that planting date affects soybean diseases and that delayed planting is a useful management tool to reduce the risk of some diseases, especially in regions with a long planting season. However, research by Iowa agronomists shows that early planting increases the possibility of achieving maximum yield and that the level of success decreases as planting is delayed. Because of narrow planting windows for high yield, especially in northern Iowa, the value of delayed planting for disease management is less in Iowa than in other regions with a longer planting season.


Site-Specific Farming Shows Hidden Nature Of Soybean Cyst Nematode Yield Losses, Gregory L. Tylka, Carmen Sanogo, Dean Michael Tranel Apr 1998

Site-Specific Farming Shows Hidden Nature Of Soybean Cyst Nematode Yield Losses, Gregory L. Tylka, Carmen Sanogo, Dean Michael Tranel

Integrated Crop Management News

The soybean cyst nematode (SCN) is a serious and widespread pathogen of soybeans in Iowa. In fact, results of a recent random survey in Iowa indicate that SCN may be present in nearly two-thirds of the fields in the state. Unfortunately, many growers do not realize that their fields are infested with SCN. Why? Results of an Iowa State University, soybean-checkoff-funded research project using site-specific farming technology illustrate the hidden nature of SCN yield losses in Iowa fields.


Plant Oats Early To Avoid Diseases, Gary P. Munkvold Apr 1998

Plant Oats Early To Avoid Diseases, Gary P. Munkvold

Integrated Crop Management News

Oats in Iowa suffer from two major diseases, crown rust and barley yellow dwarf virus. Crown rust appears as orange leaf pustules and also causes yellowing and death of the leaves. Severely affected plants are stunted and produce little grain. The disease usually first appears in late May and can remain active throughout the rest of the season. Spores can be windblown long distances, but in Iowa some initial infections are the result of spread from local buckthorn shrubs. Buckthorn is the alternate host of the crown rust fungus, Puccinia coronata.


Scn In At Least 85 Iowa Counties, Gregory L. Tylka Apr 1998

Scn In At Least 85 Iowa Counties, Gregory L. Tylka

Integrated Crop Management News

Recently, data from several sources were compiled to determine the known distribution of the soybean cyst nematode (SCN) in Iowa. These data included results of analyses of more than 3,500 samples submitted to the Iowa State University (ISU) Plant Disease Clinic from 1994 to 1998 and nearly 400 samples collected from randomly selected sites in a survey conducted in Iowa from 1995 to 1996. Presently, SCN has been found in 85 of 99 Iowa counties. The counties where SCN has not yet been confirmed are located primarily in northeast and south central Iowa.


Corn Seed Treatments In 1998, Gary P. Munkvold Mar 1998

Corn Seed Treatments In 1998, Gary P. Munkvold

Integrated Crop Management News

The snow will be gone soon and it will be time to plant corn. El NiƱo promises to bring us a cool, wet spring, and this means seedling diseases. If you don't know which fungicidal seed treatment is on your corn seed, now is a good time to have a look at those labels on the bags and check it out. Recent trends in corn seed treatment are continuing in 1998--most seed has been treated with Maxim+Apron this year instead of the traditional, standard fungicide Captan.


Questions On White Mold Control, X. B. Yang Feb 1998

Questions On White Mold Control, X. B. Yang

Integrated Crop Management News

This winter two questions on soybean white mold have been frequently asked by growers and agronomists in agribusiness: (1) Can white mold fungus infect soybean seed and spread with the seed? and (2) What are the latest findings on the use of chemicals, especially Cobra, to control white mold by foliar spray? Plant pathologists in the north central region have been working on the answers to these questions for the past two years. Although final answers are yet to come, significant progress has been made. In this article I will address the two questions by using the latest research results.


New Information On Soybean Response To White Mold, X. B. Yang Jan 1998

New Information On Soybean Response To White Mold, X. B. Yang

Integrated Crop Management News

In collaboration with Bruce Voss, Department of Agronomy, Iowa State University, and Kevin Muhlenbruch, Northern Iowa Community College, plant pathologists at ISU evaluated approximately 750 soybean entries in the 1997 Iowa Crop Performance Test-Soybeans (ICPTS) for their response to white mold. The tests were conducted in northeastern Iowa. The data have been analyzed and compiled into a publication called White Mold Tolerance in Iowa Soybean Varieties that should be very helpful to growers in determining variety selection if white mold has been a problem in their fields. The publication also provides data from the last two years of white mold ...


Herbicide-Tolerant Crops And Plant Diseases, Soum Sanogo, X. B. Yang Jan 1998

Herbicide-Tolerant Crops And Plant Diseases, Soum Sanogo, X. B. Yang

Integrated Crop Management News

Crop management is a dynamic activity that changes as technologies are developed. During winter extension activities, there were some discussions on soybean diseases observed on Roundup-Ready soybeans. This article takes a proactive approach to address some concerns that were commonly raised about herbicide-tolerant crops, herbicides, and the occurrence of plant diseases.


Disease Control With Bt Corn, Gary P. Munkvold Jan 1998

Disease Control With Bt Corn, Gary P. Munkvold

Integrated Crop Management News

Insect pests of corn are often involved in the disease cycles of ear rot and stalk rot diseases. The European corn borer is particularly well known for its involvement in these diseases. The interaction between corn borer larvae and pathogenic fungi is threefold:

  1. wounds on the plant made by corn borers are open infection sites for fungi;
  2. corn borer larvae act as vectors of pathogenic fungi (they carry the spores directly into the wounds); and
  3. the larvae cause stress on the plant that makes it more susceptible to infection and disease.