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Plant Pathology

Integrated Crop Management News

2000

Articles 1 - 20 of 20

Full-Text Articles in Life Sciences

Sds-Tolerant Soybean Varieties For Iowa, Michael D. Uphoff Dec 2000

Sds-Tolerant Soybean Varieties For Iowa, Michael D. Uphoff

Integrated Crop Management News

Last year we began testing soybean varieties for tolerance to sudden death syndrome (SDS). Funded by checkoff dollars, we have repeated the test this year with varieties submitted to us by private companies. The SDS tolerance test was conducted in a field near Ames, Iowa. To ensure uniform and consistent disease pressure across plots, we planted dry oats infested with the SDS pathogen along with the soybean seed. Our field experiments show this method, developed by our project at Iowa State University, can provide a consistent level of disease pressure. Details of this method are available upon inquiry.


Yield Maps For Sds Management, X. B. Yang, Peter Lundeen Nov 2000

Yield Maps For Sds Management, X. B. Yang, Peter Lundeen

Integrated Crop Management News

During the winter, take the time to study your yield maps. They can provide clues for disease management. In this article, we discuss how to manage disease by using a yield map provided by Lyle Stacy of Jefferson County where sudden death syndrome (SDS) has been a problem for years. Yield reduction from SDS damage was evident this past season. Stacy followed SDS development in this field for several years and is working with his client to combat this problem. The yield map (see page 188) of this 55-acre soybean field illustrates a few tips for SDS management.


Infected Soybean Seeds, X. B. Yang Oct 2000

Infected Soybean Seeds, X. B. Yang

Integrated Crop Management News

This past growing season was unique because different regions in Iowa experienced different soybean diseases. Several of the diseases are seedborne and can cause discoloration of the seeds. Some growers may want to save their own seed this year to reduce production costs, as indicated by questions I have received on seed quality concerning seedborne diseases. The following seedborne diseases were reported as production problems in Iowa: white mold, Phomopsis diseases, Cercospora leaf spot, and bean pod mottle virus. This article discusses how to handle infected soybean seeds.


Alternatives To Tillage For Soybean Disease Management, X. B. Yang, Gary P. Munkvold Oct 2000

Alternatives To Tillage For Soybean Disease Management, X. B. Yang, Gary P. Munkvold

Integrated Crop Management News

In the 1999 growing season, sudden death syndrome and Phytophthora caused damage in some soybean fields. These fields may return to soybean next year after a 1-year rotation with corn. Often, tillage would be considered as a major management option to reduce disease risk. Because of lack of precipitation this year, use of tillage may not be wise in terms of preserving soil moisture. Other methods should be selected as alternatives for disease management for the following soybean diseases.


Tillage Alternatives For Corn Disease Management, Gary P. Munkvold Oct 2000

Tillage Alternatives For Corn Disease Management, Gary P. Munkvold

Integrated Crop Management News

Now that harvest is coming to a fast close, producers are thinking about fall tillage practices. I have seen quite a few cornfields that have already been chiseled. Fall tillage marks the beginning of disease management practices for 2001. Most disease management tactics are performed before the crop is planted, and include planning for rotation, tillage, and variety selection. The most immediate decision is whether fall tillage is appropriate for managing disease problems.


Corn Stalk Rots Taking A Bite, Gary P. Munkvold Sep 2000

Corn Stalk Rots Taking A Bite, Gary P. Munkvold

Integrated Crop Management News

During the past 2 weeks, the appearance of many cornfields has begun to deteriorate, and many plants are now dead. I have inspected several fields in western and southern Iowa and found that stalk rots are common in fields with prematurely dead plants. With early planting this year, we expect the crop to be ahead of the normal maturity schedule, but it's clear that many plants are dying prematurely, in response to a combination of dry late-season conditions and stalk rots.


Premature Defoliation In Soybean, X. B. Yang Sep 2000

Premature Defoliation In Soybean, X. B. Yang

Integrated Crop Management News

After Labor Day, some soybeans started to turn yellow, especially those in maturity groups II or earlier. However, you also may have observed premature defoliation in soybean fields planted with later maturity groups, such as group III or later. Typically, only some areas within fields have defoliated plants; in the rest of the field, the plants are still green. Such defoliation can be caused by abiotic and biotic factors such as diseases. If defoliation is caused by disease, infected areas offer a good opportunity to spot the disease, which can be helpful in future prevention.


Soybean Disease Update, X. B. Yang Aug 2000

Soybean Disease Update, X. B. Yang

Integrated Crop Management News

Bean pod mottle virus (BPMV) is prevalent this summer and damage already has occurred in some soybean fields. Because soybean mosaic virus also can produce symptoms similar to BPMV, a test kit is sometimes necessary for correct disease identification. The Iowa State University "Plant Disease Clinic" provides a service to test for BPMV with an identification kit manufactured by Agdia. The kit is easy to use and produces results quickly. Submit fresh leaves from suspected plants (root tissue is not needed) to the ISU Plant Disease Clinic at Department of Plant Pathology, 323 Bessey, Iowa State University, Ames, IA 50011.


Midsummer Soybean Diseases, X. B. Yang Aug 2000

Midsummer Soybean Diseases, X. B. Yang

Integrated Crop Management News

The unusual weather this year has resulted in a diversity of soybean diseases. Both insect-vectored viral and fungal diseases are prevalent in Iowa, similar to diseases typical of southern soybean production states. This article discusses the diseases that you are likely to find during summer disease scouting (see table on page 148).


Sds Shows Up In Early Summer, X. B. Yang, Mark W. Carlton Jul 2000

Sds Shows Up In Early Summer, X. B. Yang, Mark W. Carlton

Integrated Crop Management News

Sudden death syndrome (SDS) generally strikes soybean around the middle of August in Iowa. Because of the unusual weather this growing season, the disease is showing up much earlier and was reported last week from several southern Iowa counties. The fields that we visited last week had several disease patches in poor drainage areas. Plants in these areas showed intervienal necrosis on leaves and root rot symptoms. The lower portion of stems, when they were split, was gray. In some plants, bluish fungal colonies could be seen on the roots, but these colonies were not as common as in plants ...


Phytophthora Race 25 And Soybean 1k Gene, X. B. Yang, Michael D. Uphoff Jul 2000

Phytophthora Race 25 And Soybean 1k Gene, X. B. Yang, Michael D. Uphoff

Integrated Crop Management News

Phytophthora has many races and the Rps-1k gene confers resistance to many of them. The 1k gene has been widely bred into soybeans to manage Phytophthora root rot. It has been very effective in management of Phytophthora; however, this summer we have received many reports of Phytophthora root rot on soybean varieties with the 1k gene. Recently, we have observed an increased prevalence of a new race in Iowa that can overcome the 1k gene called race 25. Growers are wondering why the 1k gene is not working, and if they can test to determine whether their fields contain race ...


Early Summer Soybean Diseases, X. B. Yang Jul 2000

Early Summer Soybean Diseases, X. B. Yang

Integrated Crop Management News

After the dry, warm planting season, most areas in Iowa have received more rain than predicted. These conditions have lead to various disease problems. The diseased plant samples sent to the Iowa State University Plant Disease Clinic and the questions received can be divided into root diseases and foliar diseases. This article summarizes these disease problems and how they may influence the coming season.


Controlling Leaf Diseases In Seed Corn In 2000, Gary P. Munkvold, Charlie Martinson Jun 2000

Controlling Leaf Diseases In Seed Corn In 2000, Gary P. Munkvold, Charlie Martinson

Integrated Crop Management News

Now is the time to be looking for early symptoms of leaf diseases in seed corn. The dry conditions of the early season were not favorable for reproduction and spread of these fungi, but recent rains may be sufficient to initiate some infections. Seed corn presents different challenges (and opportunities) when it comes to disease management. Some unique features of seed production compared with grain production are as follows.


What's Next For Stewart's Disease?, X. B. Yang Jun 2000

What's Next For Stewart's Disease?, X. B. Yang

Integrated Crop Management News

Seedling infection by Stewart's disease (greater than 30 percent) has been reported in some southern Iowa fields planted to field corn. The disease also was reported by Iowa State University field specialists-crops in field corn in central and northern Iowa. Stewart's disease is spread by overwintering flea beetle adults as they feed on corn seedlings. Overwintering flea beetle populations have declined, so questions are focused on what happens next. This article gives some questions and answers about Stewart's disease as the growing season progresses.


Races Of Phytophthora, X. B. Yang, Michael D. Uphoff Jun 2000

Races Of Phytophthora, X. B. Yang, Michael D. Uphoff

Integrated Crop Management News

Phytophthora root rot is a well-known disease to Iowa soybean growers. Although the disease has been under control, with no large-scale severe outbreaks, it continues to be a production concern and causes damage in scattered areas because of the development of new races. In the last 2 years, reports have increased for Phytophthora root rot from varieties with the Rps1k gene (or k-gene). Despite the relatively dry spring thus far, we have received reports of Phytophthora root rot on varieties with the Rps1k gene.


Scouting For Soybean Seedling Diseases In 2000, X. B. Yang Jun 2000

Scouting For Soybean Seedling Diseases In 2000, X. B. Yang

Integrated Crop Management News

The relatively dry spring has provided good conditions for controlling postemergence damping-off. Seedling disease problems this season are lighter than usual after soybean emergence. However, the rain in past 2 weeks in some regions of Iowa has been followed with a few reports of seedling diseases. The ISU Plant Disease Clinic also has received samples of infected soybean seedlings. This article discusses some seedling diseases of soybeans that growers may see this season.


More On Stewart's Wilt, X. B. Yang May 2000

More On Stewart's Wilt, X. B. Yang

Integrated Crop Management News

Iowa State University Extension continues to receive questions on Stewart's wilt, a relatively new corn disease for many Iowa producers. This article gives some of the most common questions, along with input from my research and extension colleagues on what is currently known.


Severe Risk For Stewart's Disease, Paul D. Esker, Forrest W. Nutter Jr. May 2000

Severe Risk For Stewart's Disease, Paul D. Esker, Forrest W. Nutter Jr.

Integrated Crop Management News

Stewart's disease of corn, also known as Stewart's wilt, is caused by the bacterium Pantoea stewartii. The 2000 growing season is predicted to be a very severe year for this disease, largely because of six successive winters with above-average monthly temperatures that have favored the survival of the insect vector for this disease, the corn flea beetle (Chaetocnema pulicaria). There are commonly two stages to the disease. Initially, leaf lesions that are off-green to yellow extend along the leaf veins, followed by mild-to-severe early seedling "blight" symptoms.


Soybean Seed Treatments For 2000, X. B. Yang Apr 2000

Soybean Seed Treatments For 2000, X. B. Yang

Integrated Crop Management News

Dry weather conditions are predicted for this year's growing season. Although soybean seedling disease is generally not a concern under dry conditions, I have received questions on

  1. seed treatments because of the early planting of soybeans in March
  2. the effects of seed discoloration on seed quality, and
  3. new seed treatment chemicals on the market.


North Central White Mold Web Site, X. B. Yang Mar 2000

North Central White Mold Web Site, X. B. Yang

Integrated Crop Management News

In the past 4 years, soybean pathologists in the north central region have been working on a coordinated project to find solutions of controlling soybean white mold. A new white mold Web site has been developed from this program for the North Central Soybean Research Program, a check-off dollar program. The site is hosted at University of Wisconsin at http://www.plantpath.wisc.edu/ncsrpwhitemold/