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Occurrence Of Putative Endornaviruses In Non-Cultivated Plant Species And Characterization Of A Novel Endornavirus In Geranium Carolinianum, Rachel Herschlag Nov 2017

Occurrence Of Putative Endornaviruses In Non-Cultivated Plant Species And Characterization Of A Novel Endornavirus In Geranium Carolinianum, Rachel Herschlag

LSU Master's Theses

Endornaviruses are RNA viruses, which can infect plants yet cause no apparent symptoms. To date, most descriptions of endornaviruses infecting plants have been in cultivated species. A survey for endornaviruses in non-cultivated plants was initiated in 2015 and continued through 2017 in Baton Rouge, Louisiana. Two hundred and seven plant species were tested for distinctive dsRNA profiles by selective extraction and gel electrophoresis, of which seven contained endornavirus-like dsRNA. RT-PCR amplification of an endornavirus-specific sequence supported the endornavirus nature of six of the seven samples. Of the six host species, one species, Geranium carolinianum was confirmed as being infected with ...


2015 Evaluation Of Commercial Seed Treatments On Soybean At Three Locations In Iowa, Alison E. Robertson, Mauricio Serrano, Stith N. Wiggs Jun 2017

2015 Evaluation Of Commercial Seed Treatments On Soybean At Three Locations In Iowa, Alison E. Robertson, Mauricio Serrano, Stith N. Wiggs

Alison Robertson

In 2015, 13 currently available commercial seed treatments were evaluated at three locations in Iowa. Seed treatments that reduce the risk of seedling diseases, soybean cyst nematode (SCN) and sudden death syndrome (SDS) were included in the trial. The goal of the trials is to provide information of the effect of commercial seed treatments on stand count, disease incidence and severity, and yield of soybean. Funding is provided by Iowa Soybean Association.


Performance Of Scn-Resistant Soybean Varieties In Iowa In 2016, Greg Tylka Apr 2017

Performance Of Scn-Resistant Soybean Varieties In Iowa In 2016, Greg Tylka

Gregory Tylka

Soybean varieties that are resistant to the soybean cyst nematode (SCN) are essential tools for managing the pest. Resistance to SCN requires multiple genes, and soybean varieties bred to be resistant may not contain all of the resistance genes necessary to provide maximum nematode control. Consequently, SCN control can vary greatly among resistant soybean varieties, just as yield.

Iowa State University evaluates the SCN control and yield of SCN-resistant soybean varieties in field experiments conducted throughout Iowa annually. The effort is supported, in part, by soybean checkoff funds from the Iowa Soybean Association.


More Scn-Resistant Soybean Varieties Than Ever, But Diversity Of Resistance Is Lacking, Greg Tylka Apr 2017

More Scn-Resistant Soybean Varieties Than Ever, But Diversity Of Resistance Is Lacking, Greg Tylka

Gregory Tylka

Nearly 40 years after its discovery in the upper Midwest, the soybean cyst nematode (SCN) continues to be a highly damaging pathogen of soybeans in Iowa and surrounding soybean-producing states. SCN is most damaging in hot, dry growing seasons, but yield losses of 10% to 25% or more can occur in years when temperatures are moderate and rainfall is average or above average. Growing SCN-resistant soybean varieties can slow the build-up of SCN population densities (numbers) in the soil and produce profitable soybean yields in SCN-infested fields.


Soybean Top Dieback Shows Up In Iowa Again, Xiao-Bing Yang, John E. Sawyer Mar 2017

Soybean Top Dieback Shows Up In Iowa Again, Xiao-Bing Yang, John E. Sawyer

John E. Sawyer

Extension field agronomists report the occurrence of soybean top dieback in northeastern Iowa soybean fields this week. Soybean top dieback symptoms have shown up occasionally since it was first reported by Jim Fawcett and Jerry Long in Cedar County a few years ago. Last year it was also found in eastern and central Iowa.


Last County In Iowa Found Infested With Scn, Greg Tylka, Brian Lang Jan 2017

Last County In Iowa Found Infested With Scn, Greg Tylka, Brian Lang

Integrated Crop Management News

More than 100 fields throughout Iowa were surveyed for the presence of the soybean cyst nematode (SCN) in 2016 in a project sponsored by the ISU Soybean Research Center and the Iowa Soybean Association (ISA). Soil samples were collected by Iowa State University Extension and Outreach field agronomists and ISA staff and interns and sent to the ISU Plant and Insect Diagnostic Clinic for processing.


Development Of Methods To Study Plant-Parasitic Nematode Chemotaxis And The Effect Of Ilevo And Votivo Seed Treatments On The Soybean Cyst Nematode, Heterodera Glycines, Augustine Quirarte Beeman Jan 2017

Development Of Methods To Study Plant-Parasitic Nematode Chemotaxis And The Effect Of Ilevo And Votivo Seed Treatments On The Soybean Cyst Nematode, Heterodera Glycines, Augustine Quirarte Beeman

Graduate Theses and Dissertations

Nematode-protectant seed treatments for controlling the soybean cyst nematode, Heterodera glycines, have been introduced for integration into existing nematode management plans. Several seed treatments labeled for H. glycines control are currently available, with more expected in the near future. This dissertation describes i) tools to study nematode chemotaxis to chemicals and roots and ii) assessment of two commercial seed treatments, ILeVO (active ingredient: fluopyram) and VOTiVO (active ingredient: Bacillus firmus I-1582), on important H. glycines life processes.

The first objective was to develop and test two novel microfluidic chips to study chemotaxis of plant-parasitic nematodes to chemicals (“basic chip”) and ...


Performance Of Scn-Resistant Soybean Varieties In Iowa In 2016, Greg Tylka Dec 2016

Performance Of Scn-Resistant Soybean Varieties In Iowa In 2016, Greg Tylka

Integrated Crop Management News

Soybean varieties that are resistant to the soybean cyst nematode (SCN) are essential tools for managing the pest. Resistance to SCN requires multiple genes, and soybean varieties bred to be resistant may not contain all of the resistance genes necessary to provide maximum nematode control. Consequently, SCN control can vary greatly among resistant soybean varieties, just as yield.

Iowa State University evaluates the SCN control and yield of SCN-resistant soybean varieties in field experiments conducted throughout Iowa annually. The effort is supported, in part, by soybean checkoff funds from the Iowa Soybean Association.


What’S The Situation With Scn In Your Fields?, Greg Tylka Oct 2016

What’S The Situation With Scn In Your Fields?, Greg Tylka

Integrated Crop Management News

The soybean cyst nematode (SCN) is capable of causing serious yield loss on soybeans every year and is widespread throughout Iowa and much of the Midwest. In the “good ole days,” a farmer was “good to go” with SCN management if he or she knew what fields were infested with the nematode and then grew SCN-resistant soybean varieties in rotation with the nonhost crop corn. Nowadays, though, things are a little more complicated.

The fact is, your SCN numbers may be building up unbeknownst to you. This buildup can go unrecognized because a soybean crop often does not appear stressed ...


More Scn-Resistant Soybean Varieties Than Ever, But Diversity Of Resistance Is Lacking, Greg Tylka Oct 2016

More Scn-Resistant Soybean Varieties Than Ever, But Diversity Of Resistance Is Lacking, Greg Tylka

Integrated Crop Management News

Nearly 40 years after its discovery in the upper Midwest, the soybean cyst nematode (SCN) continues to be a highly damaging pathogen of soybeans in Iowa and surrounding soybean-producing states. SCN is most damaging in hot, dry growing seasons, but yield losses of 10% to 25% or more can occur in years when temperatures are moderate and rainfall is average or above average. Growing SCN-resistant soybean varieties can slow the build-up of SCN population densities (numbers) in the soil and produce profitable soybean yields in SCN-infested fields.


Corn Following Corn In 2008, Mahdi Al-Kaisi, Roger W. Elmore, Antonio P. Mallarino, Palle Pedersen, Alison E. Robertson, John E. Sawyer, Jon J. Tollefson Jul 2016

Corn Following Corn In 2008, Mahdi Al-Kaisi, Roger W. Elmore, Antonio P. Mallarino, Palle Pedersen, Alison E. Robertson, John E. Sawyer, Jon J. Tollefson

John E. Sawyer

Corn following corn is in rough shape in areas across Iowa. Many wonder what is happening. The crop’s condition in general is not normal for this time of year. For example, last Sunday the USDA rated this year’s Iowa corn crop as 54 percent in ‘Good’ to ‘Excellent’ condition and 15 percent is ‘Poor’ or ‘Very Poor.’ Last year 72 percent was rated ‘Good’ to ‘Excellent’ and 5 percent was in ‘Poor’ or ‘Very Poor’ condition during the same week. Average plant height as of Sunday was 24 inches compared to 40 inches at end of the same ...


Towards A Molecular Method For The Detection Of Leaf Rust In Lowbush Blueberry, Steven Valentino May 2016

Towards A Molecular Method For The Detection Of Leaf Rust In Lowbush Blueberry, Steven Valentino

Honors College

Thekopsora minima, or leaf rust, is a fungal pathogen that infects Vaccinium angustifolium (lowbush blueberry), an economically important crop to the state of Maine. T. minima undergoes a complicated life cycle that contains five unique spore stages. It causes abscissions in the leaves of plants that may consequently lower yields in the next growing cycle if leaf drop is severe. Currently, growers are instructed to apply fungicides in late July to prevent further infection. However, this is often not effective due to poor timing. Data on spore release patterns would be beneficial to elucidate the infection period. However, microscopic identification ...


2015 Evaluation Of Commercial Seed Treatments On Soybean At Three Locations In Iowa, Alison E. Robertson, Mauricio Serrano, Stith N. Wiggs Apr 2016

2015 Evaluation Of Commercial Seed Treatments On Soybean At Three Locations In Iowa, Alison E. Robertson, Mauricio Serrano, Stith N. Wiggs

Integrated Crop Management News

In 2015, 13 currently available commercial seed treatments were evaluated at three locations in Iowa. Seed treatments that reduce the risk of seedling diseases, soybean cyst nematode (SCN) and sudden death syndrome (SDS) were included in the trial. The goal of the trials is to provide information of the effect of commercial seed treatments on stand count, disease incidence and severity, and yield of soybean. Funding is provided by Iowa Soybean Association.


Research Shows Extra Cover Crop Growth Prior To Soybeans Provides Benefits, Daren S. Mueller, Michael J. Castellano Mar 2016

Research Shows Extra Cover Crop Growth Prior To Soybeans Provides Benefits, Daren S. Mueller, Michael J. Castellano

Integrated Crop Management News

This study, funded by the United Soybean Board (USB), was conducted to understand the potential for cover crops to perform in a corn and soybean rotation, and to collect data on the performance of cover crops in those rotations in relation to the timing of termination.


Top Dieback In Corn: Is Anthracnose The Cause?, Alison E. Robertson Feb 2016

Top Dieback In Corn: Is Anthracnose The Cause?, Alison E. Robertson

Alison Robertson

Over the past week, I have had calls and e-mails regarding anthracnose top dieback in corn. First, a word of caution: Not all top dieback is caused by the anthracnose pathogen. Death of top leaves may be due to one or more of several factors that include hybrid characteristics, environmental stress, and corn borer damage. Bob Nielsen at Purdue University discusses these various factors in an article titled Top Leaf Death in Corn.


Storing Fungicides Safely, Alison E. Robertson, Richard O. Pope Feb 2016

Storing Fungicides Safely, Alison E. Robertson, Richard O. Pope

Alison Robertson

Growers who stocked up on fungicides for the 2005 growing season due to the threat of Asian soybean rust will likely be facing fungicide storage issues this winter, especially since it is likely that most products cannot be returned. The good news is that most fungicides have a shelf life of at least two years--and probably longer--assuming they are stored correctly. Optimum storage conditions are cool, dry conditions, away from sunlight. Storage temperatures should not go below freezing; however, if a fungicide does freeze, then slowly thaw it out at room temperature.


Managing Two Soybean Pests To Optimize Yield, Erin W. Hodgson, Gregory L. Tylka, Aaron J. Gassmann Feb 2016

Managing Two Soybean Pests To Optimize Yield, Erin W. Hodgson, Gregory L. Tylka, Aaron J. Gassmann

Integrated Crop Management News

Soybean cyst nematode (SCN) and soybean aphid (SBA) are important soybean pests in the north-central region. Soybean varieties with host plant resistance for SCN (PI88788) and SBA (Rag1) can suppress pest populations and subsequently protect yield. In addition, seed treatments are becoming widely adopted and now can include a nematacide, fungicides and insecticide. Combining host plant resistance with seed treatments could potentially further protect yield. This article summarizes a 3-year research effort, funded by the soybean checkoff through a grant from the Iowa Soybean Association, that evaluated interactions among these two pests, host plant resistance, and seed treatments.


Scn Resistance Continues To Pay Twice In 2015, Gregory L. Tylka Jan 2016

Scn Resistance Continues To Pay Twice In 2015, Gregory L. Tylka

Integrated Crop Management News

Resistant soybean varieties are a vital tool for managing the soybean cyst nematode (SCN). These soybean varieties must contain several genes to be fully resistant to the nematode. Not all SCN-resistant varieties contain a full set of resistance genes. Consequently, SCN-resistant soybean varieties can vary greatly in their agronomic performance and the SCN control that they provide.


Stalk And Ear Diseases In Bt And Non-Bt Corn Hybrids In Northeast Iowa, 2000, Gary P. Munkvold Nov 2015

Stalk And Ear Diseases In Bt And Non-Bt Corn Hybrids In Northeast Iowa, 2000, Gary P. Munkvold

Gary P. Munkvold

Ear rot and stalk rot diseases are not under adequate control by direct genetic resistance in corn hybrids, and cultural or chemical control methods do not exist or are not effective. Because infection by ear- and stalk-rotting fungi sometimes occurs through European corn borer (ECB) injury, there is a potential to reduce infection through the use of Bt hybrids, which are resistant to ECB. In previous research, we have shown that Fusarium ear rot, caused by Fusarium moniliforme and Fusarium proliferatum, is reduced in Bt hybrids with the YieldGard genes. We also found that the primary mycotoxins produced by these ...


Ecological Specialization Of Tubakia Iowensis, And Searching For Variation In Resistance To Bur Oak Blight, Ashley Marie West Jan 2015

Ecological Specialization Of Tubakia Iowensis, And Searching For Variation In Resistance To Bur Oak Blight, Ashley Marie West

Graduate Theses and Dissertations

Tubakia iowensis was recently recognized and described as the causative agent of bur oak blight. The pathogen causes vein necrosis and early season leaf death on Quercus macrocarpa (bur oak). Tubakia sp. B, an undescribed species, was isolated from bur oak and other oaks and was found to be morphologically indistinguishable from T. iowensis. In chapter 2, T. iowensis and Tubakia sp. B differed in causing a greater amount of necrosis on inoculated leaf blade tissue and in causing less petiole death and fewer conidiomata (pustules) after inoculation of expanding shoots. Both Tubakia spp. caused vein necrosis, but Tubakia sp ...


Seedborne Black Aspergillus Species As Maize Seedling Pathogens: Role Of Fumonisin Production And Interaction With Soilborne Pythium Species, Laura Kaelia Weieneth Jan 2015

Seedborne Black Aspergillus Species As Maize Seedling Pathogens: Role Of Fumonisin Production And Interaction With Soilborne Pythium Species, Laura Kaelia Weieneth

Graduate Theses and Dissertations

Twenty-six strains of black Aspergillus (Aspergillus section Nigri) were studied as seedling pathogens of maize. There were two major research components. The first component was an evaluation of the pathogenicity of isolates from several black Aspergillus species and a comparison of the pathogenicity of isolates with and without fumonisin production. This was accomplished by testing inoculated seeds in warm germination and cold tests, and by evaluating growth of inoculated seeds in rolled paper towel assays. In the second component, four of these species were selected for evaluation of interactions between Aspergillus and Pythium as a seedling disease complex in maize ...


Bacterial Wilt Of Cucurbits: Impact Of Plant Age On Symptom Progression And Pathogen Movement And Locating Genes Associated With Host Preference And Pathogenesis In E. Tracheiphila, Qian Liu Jan 2015

Bacterial Wilt Of Cucurbits: Impact Of Plant Age On Symptom Progression And Pathogen Movement And Locating Genes Associated With Host Preference And Pathogenesis In E. Tracheiphila, Qian Liu

Graduate Theses and Dissertations

Bacterial wilt of cucurbits is a devastating disease of cucurbit crops in the mid-Atlantic region of the USA. Caused by Erwinia tracheiphila, it is transmitted by striped (Acalymma vittatum (F.)) and spotted (Diabrotica undecimpunctata howardi (Barber)) cucumber beetles. The management of bacterial wilt relies primarily on the control of cucumber beetles with insecticides. However, alternative management strategies are needed due to the high cost of insecticides and their negative impact on the environment. Understanding bacterial wilt etiology and the ecology of E. tracheiphila may provide insights to help control bacterial wilt of cucurbits.

The first objective of my thesis research ...


Emerging Issues In The U.S. Corn Belt: Infection Of Corn By Clavibacter Michiganensis Subsp. Nebraskensis And Use Of Foliar Fungicides To Protect Yield, Salome Mallowa Obura Jan 2015

Emerging Issues In The U.S. Corn Belt: Infection Of Corn By Clavibacter Michiganensis Subsp. Nebraskensis And Use Of Foliar Fungicides To Protect Yield, Salome Mallowa Obura

Graduate Theses and Dissertations

Currently two major issues pertaining to disease management in corn production in the US Corn Belt are the spread of Goss's wilt and leaf blight caused by Clavibacter michiganensis subsp. nebraskensis (Cmn), and the use of foliar fungicides on corn for `plant health' benefits. This dissertation presents data regarding infection of corn by Cmn, and fungicide effects on disease management and yield.

Greenhouse and laboratory research was undertaken to determine if infection of corn by Cmn may occur without severe wounding, such as that caused by hail, sand blasting or wind damage. Corn plants with no obvious wounding were ...


The Role Of Fusarium Mycotoxins In Seedling Infection Of Soybeans, Wheat And Maize, Tracy L. Bruns Jan 2015

The Role Of Fusarium Mycotoxins In Seedling Infection Of Soybeans, Wheat And Maize, Tracy L. Bruns

Graduate Theses and Dissertations

Fusarium graminearum and Fusarium verticillioides are fungal plant pathogens that can cause yield losses, reductions in grain quality, and produce mycotoxins that can cause serious diseases in animals and humans when contaminated grain is consumed. Both pathogens can infect and cause disease in seedlings. F. graminearum infects cereals and other crops and produces mycotoxins including deoxynivalenol (DON), which can act as a virulence factor for Gibberella ear rot in maize and head blight of wheat. F. verticillioides infects maize and produces fumonisins, a group of mycotoxins with phytotoxic properties. Previous research into the role of these mycotoxins in seedling diseases ...


Detection And Management Of Colletotrichum Acutatum Sensu Lato On Strawberry, Xiaoyu Zhang Jan 2015

Detection And Management Of Colletotrichum Acutatum Sensu Lato On Strawberry, Xiaoyu Zhang

Graduate Theses and Dissertations

Colletotrichum acutatum sensu lato, one of the most economically damaging pathogens of strawberry, is the primary causal agent of anthracnose fruit rot (AFR). A key challenge in managing AFR is detecting the pathogen on asymptomatic plants. To meet this need, a loop-mediated isothermal amplification (LAMP) assay was developed that incorporated two sets of primers: LITSG1 targeted on the ITS region of ribosomal DNA and Ltub2 on the β-tubulin 2 gene. In pure culture assays, Ltub2 was specific for detection of C. acutatum, whereas LITSG1 detected C. acutatum and two additional anthracnose pathogens, C. gloeosporioides and C. fragariae. LITSG1 had 10-fold ...


Raffaelea Spp. From Five Ambrosia Beetles In The Genera Xyleborinus And Cyclorhipidion (Coleoptera: Curcurlionidae: Scolytinae: Xyleborini), Yeganeh Gharabigloozare Jan 2015

Raffaelea Spp. From Five Ambrosia Beetles In The Genera Xyleborinus And Cyclorhipidion (Coleoptera: Curcurlionidae: Scolytinae: Xyleborini), Yeganeh Gharabigloozare

Graduate Theses and Dissertations

Five undescribed species of Raffaelea (Ophiostomatales), as well as Raffaelea sulphurea, were isolated and illustrated from the ambrosia beetle tribe Xyleborini: Raffaelea sulphurea and Raffaelea sp. A from Xyleborinus saxeseni; Raffaelea sp. B and Raffaelea sp. C from Xyleborinus attenuatus; Raffaelea sp. D from Xyleborinus gracilis; Raffaelea sp. F from Cyclorhipidion bodoanum; and Raffaelea sp. G from C. pelliculosum.

Each fungal symbiont was isolated from a single beetle host species or its galleries and characterized by culture morphology and DNA sequencing. Analysis of of 18S rDNA and translocation elongation factor sequences of five undescribed symbionts (Raffaelea sulphurea, Raffaelea sp. B ...


Mid-Season Soybean Diseases Out In Full Force: How To Send A Sample To Isu Diagnostic Clinic, Laura C.H. Jesse, Daren S. Mueller Jul 2014

Mid-Season Soybean Diseases Out In Full Force: How To Send A Sample To Isu Diagnostic Clinic, Laura C.H. Jesse, Daren S. Mueller

Integrated Crop Management News

Soybean samples have been arriving almost daily at the ISU Plant and Insect Diagnostic Clinic this year. Early season problems were primarily damping off diseases and problems with herbicide carryover or sometimes a combination of the two.


Northern Leaf Blight Prevalent In Iowa, Alison E. Robertson Jul 2014

Northern Leaf Blight Prevalent In Iowa, Alison E. Robertson

Integrated Crop Management News

Northern corn leaf blight (NCLB) has been reported in numerous fields in Iowa. Most of the reports have come from central and western Iowa, but since the pathogen that causes this disease is spread by wind and rain, the disease could be more widespread.


Effects Of Ilevo® On Soybean Sudden Death Syndrome And Soybean Cyst Nematode, Edward R. Zaworski Jan 2014

Effects Of Ilevo® On Soybean Sudden Death Syndrome And Soybean Cyst Nematode, Edward R. Zaworski

Graduate Theses and Dissertations

Fusarium virguliforme, the causal agent of soybean sudden death syndrome (SDS), and Heterodera glycines, soybean cyst nematode (SCN), are two of the most important pathogens of soybean. Host resistance is currently the main management strategy for both pathogens, and there are few other options available for each pathogen. Seed treatments are now an option for farmers for use of pesticides in early plant development. Bayer CropScience recently registered a seed treatment, ILeVO® (fluopyram), with reported activity against both SDS and SCN. The research described in the following manuscript tested ILeVO® in different combinations with currently available seed treatment products for ...


Influence Of Heterodera Glycines Infection, Plant Age And Water Availability On Foliar Symptoms Of Sudden Death Syndrome, Root Symptom Severity And Root Morphology Of Soybean Plants Infected By Fusarium Virguliforme, Nenad Tatalović Jan 2014

Influence Of Heterodera Glycines Infection, Plant Age And Water Availability On Foliar Symptoms Of Sudden Death Syndrome, Root Symptom Severity And Root Morphology Of Soybean Plants Infected By Fusarium Virguliforme, Nenad Tatalović

Graduate Theses and Dissertations

Fusarium virguliforme Aoki, O'Donnell, Homma and Lattanzi (FV), a causal organism of sudden death syndrome (SDS), and Heterodera glycines Ichinohe, the soybean cyst nematode (SCN), are two of the most important soil-borne pathogens affecting soybean production in the USA. These pathogens often occur together in production fields and interact, which results in significant yield losses. In co-infected plants, SDS symptoms appear earlier and are more severe than in plants infected by FV alone. However, the mechanism of the SCN-FV interaction remains unclear. Fusarium virguliforme is able to infect soybean plants of different growth stages, but plants infected at younger ...