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Iowa State University

Plant Sciences

Proceedings of the Integrated Crop Management Conference

1994

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Weed Resistance Assessment Program (Wrap), Bob Hartzler Dec 1994

Weed Resistance Assessment Program (Wrap), Bob Hartzler

Proceedings of the Integrated Crop Management Conference

The phenomena of herbicide resistance is not a new concern; triazine resistant weeds were first reported in the late 1960's. Since then, resistance has developed to many other important classes of herbicides. Although there are isolated infestations of triazine resistant weeds across Iowa, these weeds are not considered a major problem in the state. Recent shifts in herbicide use patterns has increased the potential for the development of resistant biotypes. This paper will describe factors which influence the development of resistance and how weed management programs can be manipulated to minimize the potential for resistance.


Foliar Fungicides In Seed Corn Production, C. A. Martinson, F. W. Nutter Jr., Stephen N. Wegulo, J. M. Rivera C. Dec 1994

Foliar Fungicides In Seed Corn Production, C. A. Martinson, F. W. Nutter Jr., Stephen N. Wegulo, J. M. Rivera C.

Proceedings of the Integrated Crop Management Conference

Since 1982, we have conducted a program to determine the fungicides that may be effective for controlling foliar diseases in inbred and hybrid com. For the past seven years we have limited our research to only inbreds or sister line hybrids. In 1990, we started a cooperative program with seed companies and have conducted our research in commercial seed production fields in five greatly different years in terms of weather patterns. Thirty experiments have been established in seed production fields and 25 fields have been harvested for yield. Five experiments were abandoned because of herbicide injury interactions (2,4-D) with ...


The 1994 Iowa Crop- Did We Get It Right?, Garren O. Benson Dec 1994

The 1994 Iowa Crop- Did We Get It Right?, Garren O. Benson

Proceedings of the Integrated Crop Management Conference

The answer to the question raised in the title is yes. The October Crop Report estimated Iowa corn and soybean yields at 150 and 51 bu/ac respectively. If maintained in the November and January reports both yields would be records. The prior corn record was 147 bu/ ac in 1992. The soybean yield is an incredible 7 bu/ ac over the previous record of 44 bu/ac set in 1992. If 1994 yield estimates fit historic patterns, the final estimate in January may be even higher than those indicated in Table 1. The 1994 crop is a complete reversal ...


No-Till And Soybean Diseases In Iowa, X. B. Yang, Fekede Workneh, Gregory Tylka Dec 1994

No-Till And Soybean Diseases In Iowa, X. B. Yang, Fekede Workneh, Gregory Tylka

Proceedings of the Integrated Crop Management Conference

Conventional tillage methods are effective means of controlling plant disease because completely burying crop residues destroys plant pathogens and breaks disease cycles (Boosalis et al, 1986). Today, cropping practices are shifting to surface-tillage systems to offset the rising cost of production and to comply with USDA/ ASCS mandatory soil conservation requirements which have a deadline of 1 January 1995. The percentage of no-till soybean fields in Iowa was 19% of total acreage in 1993. It is predicted that the total acreage of conservation tillage in Iowa will increase to 11 million acres by 1995. Because conservation tillage practices leave crop ...


Nutrient Use Efficiency: An Ecological Approach, Cynthia A. Cambardella Dec 1994

Nutrient Use Efficiency: An Ecological Approach, Cynthia A. Cambardella

Proceedings of the Integrated Crop Management Conference

The practice of agriculture by humankind intentionally disturbs the nutrient and energy balance (especially Nand C) of natural ecological systems to produce the food, feed, and fiber needed to sustain human activities. These disturbed ecological systems are generally referred to as agroecosystems. A sustainable agroecosystem is one managed for the long-term profitable production of food, feed, or fiber while utilizing the full potential of biological, chemical and physical processes to conserve natural resources and minimize environmental damage (Elliott et al., 1993). Low nutrient-use efficiency is a major factor contributing to the non-sustainability of agroecosystems. To improve efficiency, a more complete ...


Site Specific Management: The Pros, The Cons, And The Realities, F. J. Pierce, P. C. Robert, G. Mangold Dec 1994

Site Specific Management: The Pros, The Cons, And The Realities, F. J. Pierce, P. C. Robert, G. Mangold

Proceedings of the Integrated Crop Management Conference

Site specific management (SSM) for agriculture involves the variable management of soils and crops according to localized conditions within a field. Known by many other names, such as "Grid Farming", "Farming by Soils" or "Variable Rate Technology (VRT), SSM is a rapidly emerging set of technologies that allow farmers to manage their soils and crops on-the-go as equipment moves across a field. In essence, SSM is about doing the right thing, at the right time, in the right place, in the right way. Thus, SSM is intuitively appealing because it represents a means of improving the economic and environmental performance ...


Diseases Of Corn And Soybeans In 1994, Gary P. Munkvold Dec 1994

Diseases Of Corn And Soybeans In 1994, Gary P. Munkvold

Proceedings of the Integrated Crop Management Conference

Growing conditions in 1994 were quite favorable overall, but the variability of weather this year resulted in some areas with substantially wetter or drier than normal conditions for some portion of the season. Serious disease problems are often associated with weather conditions outside the norms. Some diseases can be expected to appear almost every year, and 1994 was typical in regard to some of the common corn and soybean diseases. In corn, there were some problems with Fusarium crovm rot, common smut, northern leaf blight, Gibberella ear rot and stalk rots caused by Gibberella zeae and Colletotrichum graminicola {anthracnose). However ...


Soybean Cyst Nematode- Biology And Management, Gregory L. Tylka Dec 1994

Soybean Cyst Nematode- Biology And Management, Gregory L. Tylka

Proceedings of the Integrated Crop Management Conference

Soybean cyst nematode, Heterodera glycines, is a small, unsegmented plant-parasitic roundworm that attacks the roots of soybeans. While many plant-parasitic nematodes are believed to be endemic or native to the United States, soybean cyst nematode is believed to have been introduced from Japan. Soybean cyst nematode was first discovered in the United States in 1954 in North Carolina (Winstead et al., 1955), and has since spread to 25 additional states in the Southeast and Midwest (Noel, 1992). It was first discovered in Iowa in Winnebago County in 1978. In 1994, soybean cyst nematode was identified for the first time in ...


Influence Of Aphanomyces Root Rot On Alfalfa Health And Forage Yields, Craig R. Grau, D. W. Weirsma, D. J. Undersander Dec 1994

Influence Of Aphanomyces Root Rot On Alfalfa Health And Forage Yields, Craig R. Grau, D. W. Weirsma, D. J. Undersander

Proceedings of the Integrated Crop Management Conference

Maximum alfalfa performance is achieved when grown on deep, well drained soils, while severe stand and yield losses can occur on soils that are imperfectly drained (Wing, 1909; Alva et al., 1985). In Wisconsin, nearly half of all forage production is on soils that are classified as somewhat poorly drained.


Realitites Of Providing Site-Specific Services To Customers, John E. Sawyer, Ron Milby Dec 1994

Realitites Of Providing Site-Specific Services To Customers, John E. Sawyer, Ron Milby

Proceedings of the Integrated Crop Management Conference

Site-specific agriculture has the potential to improve management of crop production inputs and efficiency of use. Improved technologies should be applied when a need is identified and implementation is feasible. Currently, technology costs and our capacity to reliably delineate or map properties affecting crop production does not always allow maximum benefit to be derived from site-specific services. This will likely improve as the costs for certain technologies decrease and there is a better understanding about variability management. Today a whole range of "new technologies" are often thrown together as the site-specific approach. These include GPS, GIS, yield monitoring, grid soil ...


Spatial Variability Of Phosphorus And Potassium In No-Till Corn And Soybean Fields, Antonio P. Mallarino Dec 1994

Spatial Variability Of Phosphorus And Potassium In No-Till Corn And Soybean Fields, Antonio P. Mallarino

Proceedings of the Integrated Crop Management Conference

Soil testing is a useful tool to evaluate soil fertility, and fertilization recommendations for phosphorus (P) and potassium (K) usually are based on soil testing. There are many potential errors involved, however. One of the most important sources of error is obtaining a representative sample in the field. A very small amount of soil needs to appropriately represent thousands of tons of soil, and usually there is significant spatial variability of nutrient levels. This is the basis for the development of technology to spatially vary the rate of fertilizer application within a field. Conventional soil sampling methods, however, are not ...


Production And Marketing Of Specialty Soybeans, Walter R. Fehr Dec 1994

Production And Marketing Of Specialty Soybeans, Walter R. Fehr

Proceedings of the Integrated Crop Management Conference

The soybean breeding project at Iowa State University has been involved in the development of soybean cultivars for specific end uses for more than 40 years. The initial objective was to develop cultivars with unique characteristics for food products, including tofu, miso, and vegetable soybeans. In the late 1960's, research began at Iowa State on the development of cultivars with modified oil composition. Until the 1980's, the interest of other public institutions and of private companies in breeding specialty cultivars was limited. The situation changed dramatically in the 1980's as more breeders in the public and private ...


Current Issues In Weed Management, Micheal D. K. Owen, Robert G. Hartzler Dec 1994

Current Issues In Weed Management, Micheal D. K. Owen, Robert G. Hartzler

Proceedings of the Integrated Crop Management Conference

Weed management is in a continual state of change, however there are several issues that will likely be major considerations for several years and reflect concerns for the environment and the economics of weed management. These issues include guaranteed performance agreements and the advisability of respray programs, herbicide resistance in weeds, herbicide resistant crops, the interaction of pesticides as it affects crop phytotoxicity and new herbicide products and associated environmental risks. This paper will briefly review these issues and provide the perspective of the authors about the impact of these issues on weed management.


The Identification And Management Of Sweet Corn Diseases, Laura E. Sweets Dec 1994

The Identification And Management Of Sweet Corn Diseases, Laura E. Sweets

Proceedings of the Integrated Crop Management Conference

Diseases can and do cause losses in sweet corn production. Various sweet corn diseases may result in germination and stand establishment problems, losses in yield and reduction in quality. Because of the extreme importance of quality in sweet corn production for either fresh market or processing along with the higher value of sweet corn, disease management in sweet corn production is an excellent opportunity to employ integrated pest management tactics. Sweet corn fields should be scouted on a regular basis to identify diseases present and to assess the severity of these diseases. Emphasis is certainly placed on preventing sweet corn ...


Seed Coatings To Improve Seed Performance, Reduce Pesticide Usage And As Production Tools In Soybeans And Corn, J. S. Burris Dec 1994

Seed Coatings To Improve Seed Performance, Reduce Pesticide Usage And As Production Tools In Soybeans And Corn, J. S. Burris

Proceedings of the Integrated Crop Management Conference

For hundreds if not thousands of years seeds have been amended with various materials to insure their survival or to improve their emergence and growth. The early Greeks and Egyptians used salts to insure seed storability and applied elemental dusts to protect the seed after it was planted. Although hot water treatments might not be considered a seed treatment they have the effect of eliminating harmful organisms while maintaining seed viability. With the discovery of the pesticidal properties of some of the heavy metals especially copper, mercury and zinc modem seed treatment as we know it today was introduced.


Soybean Cyst Nematode- Identification And Extraction Techniques, Gregory L. Tylka Dec 1994

Soybean Cyst Nematode- Identification And Extraction Techniques, Gregory L. Tylka

Proceedings of the Integrated Crop Management Conference

A major factor limiting soybean production in Iowa is parasitism by the soybean cyst nematode, Heterodera glycines. Soybean cyst nematode was identified in Carroll, Davis, Henry, and Sac Counties for the first time in 1994 and is now known to be present in 62 Iowa counties. It is very likely that the nematode is present in many other counties as well, but the nonspecific nature of the above-ground symptoms of soybean cyst nematode damage makes early identification or diagnosis of infestations difficult. Above-ground symptoms of soybean cyst nematode damage often do not appear consistently, and may be absent for several ...


Use Of Portable Chlorophyll Meters To Predict Sidedress In Requirements For Corn, Randy Killorn, Chad Berghoefer Dec 1994

Use Of Portable Chlorophyll Meters To Predict Sidedress In Requirements For Corn, Randy Killorn, Chad Berghoefer

Proceedings of the Integrated Crop Management Conference

The leaf nitrogen (N) concentration of com is related to the amount of chlorophyll in the leaf, and it may be possible to use a portable chlorophyll meter to estimate whether a crop is deficient in N and, when calibrated, to estimate the amount of N fertilizer required to attain optimum yield if the reading is below the critical value. Taking chlorophyll readings on the plant allows sampling in fields fertilized with injected N before planting. With the technology currently available it may be possible to walk through a field taking random chlorophyll readings and to predict if additional fertilizer ...


Grid Soil Sampling For Precision And Profit, N. C. Wollenhaupt, R. P. Wolkowski Dec 1994

Grid Soil Sampling For Precision And Profit, N. C. Wollenhaupt, R. P. Wolkowski

Proceedings of the Integrated Crop Management Conference

Site specific management of plant nutrients for crop production begins with an inventory of soil test levels in a field. Fertilizer recommendations are based on the expected response to addition of fertilizers as a function of soil test levels. Therefore, the accuracy of site specific fertilizer applications depends on how accurately the nutrient status of soils is mapped. Mapping accuracy usually increases as fields are divided and sampled as smaller areas.


Factors Influencing Sudden Death Syndrome And Root Health In Soybean, T. Scott Abney Dec 1994

Factors Influencing Sudden Death Syndrome And Root Health In Soybean, T. Scott Abney

Proceedings of the Integrated Crop Management Conference

Each year, soybean growers lose at least 14 percent (approximately $175,000,000 in Indiana) of their crop to disease. Root rots disease caused by particular species of Fusarium, Phytophthora, Rhizoctonia, Phialophora, and Macrophomina account for a significant portion of this annual yield loss and substantially increase yield losses above 14 percent in specific production areas in the Midwest. Yield losses due to diseases like Fusarium root rot, Phytophthora root rot, Rhizoctonia root rot, Brown stem rot, and Charcoal root rot caused by species of the fungi mentioned above have been recognized for a number of years and most soybean ...


An Integrated Approach To Control Sclerotinia Stem Rot (White Mold) In Soybean, Craig R. Grau, Eric A. Adee, Edward S. Oplinger Dec 1994

An Integrated Approach To Control Sclerotinia Stem Rot (White Mold) In Soybean, Craig R. Grau, Eric A. Adee, Edward S. Oplinger

Proceedings of the Integrated Crop Management Conference

While brown stem rot, Phytophthora root rot, sudden death syndrome and the soybean cyst nematode generally are regarded as the most significant diseases of soybean in the North Central States, Sclerotinia stem rot, also called white mold, has been a problem in Minnesota, Wisconsin and Michigan for many years. Beginning in 1992, and again in 1994, Sclerotinia stem rot developed throughout the northern range of the North Central Region. Nationally, the disease is considered to be minor because it has not involved a high percentage of the national soybean acreage. Possibly this situation has changed and Sclerotinia stem rot will ...