Plant Pathology Commons^™

Big Bud Disease In Tomatoes And Peppers, Claudia Nischwitz, Erin Petrizzo

All Current Publications

This fact sheet provides information on the symptoms of big bud on tomatoes and peppers. It reviews the disease cycle and recommendations on controlling beet leafhopper and managing big bud disease in Utah.

Reactive Oxygen Species In Plant Interactions With Aphids, Fiona L. Goggins, Hilary D. Fischer

Entomology Faculty Publications and Presentations

Reactive oxygen species (ROS) such as hydrogen peroxide and superoxide are produced in plants in response to many biotic and abiotic stressors, and they can enhance stress adaptation in certain circumstances or mediate symptom development in others. The roles of ROS in plant-pathogen interactions have been extensively studied, but far less is known about their involvement in plant-insect interactions. A growing body of evidence, however, indicates that ROS accumulate in response to aphids, an economically damaging group of phloem-feeding insects. This review will cover the current state of knowledge about when, where, and how ROS accumulate in response to aphids, …

The Impact Of Beneficial Organisms In Corn Agroecosystems, Callie Rosalind Braley

Doctor of Plant Health Program: Dissertations and Student Research

Corn is one of the world’s, and Nebraska’s, most important crops. Millions of acres are planted to corn each year in the Cornhusker State. However, each year there are a plethora of arthropod, weed, and microorganism pests that rob farmers of reaching their maximum yield potential. There are many options available to manage these pests in corn agroecosystems, but one option is often underutilized: beneficial organisms. For each pest, there are a variety of natural enemies that can assist in mitigating the damage caused by pests.

Many beneficial organisms exist, and they can be grouped by the type of pest …

Response Of Roseau Cane (Phragmites Australis) To Two Biotic Stresses: Hyalopterus Pruni And Bipolaris Yamadae, Heather E. Cizek

LSU Master's Theses

Roseau cane (Phragmites australis) is considered an invasive plant because of its ability to replace native plant species. However, in Louisiana it plays an important role protecting coastal infrastructure and being part of the marsh ecosystem in the lower Mississippi River Delta. In recent years, Roseau cane has been affected by a die-off, a problem that has also been reported in some European countries. Possible biotic and abiotic factors that have been associated with the die-off include scale insects, climate change, pollution, salinity levels, and pathogens.

In this research, the individual and combined effect of a foliar disease …

Lily Leaf Beetle, Ann Mull, Lori R. Spears

All Current Publications

The lily leaf beetle (LLB) (Coleoptera: Chrysomelidae) is an important pest from Eurasia that threatens native and cultivated true lilies (Lilium spp.) and fritillaries (Fritillaria spp.). It is also known as the red lily leaf beetle or scarlet lily beetle. LLB was first reported in North America in Montréal, Canada, in 1945 and in the U.S. in 1992 in Massachusetts, likely arriving via European shipments of lily bulbs. LLB has been detected in nine of the 10 Canadian provinces and 14 U.S. states, including the New England states, Pennsylvania, Wisconsin, Minnesota, and Washington (EDDMapS, 2021). Based on LLB’s native distribution …

Identity And Population Density Of Thrips Hawaiiensis (Insecta: Thysanoptera) In Conventional “Magallanes” Pummelo Orchard In Carmen, Davao Del Norte, Philippines, Roderick Granada, Flor Ceballo, Pio Javier

The Philippine Agricultural Scientist

A conventional “Magallanes” Pummelo orchard in Brgy. Minda, Carmen, Davao del Norte, Philippines was selected to assess thrips species composition, population density, and associated natural enemies. The insecticide treated pummelo orchard was situated adjacent to vast Cavendish banana plantations. Thrips were collected weekly from September 2017 to July 2018 from five different randomly selected flowering pummelo trees by destructive sampling and yellow sticky trap methods. Thrips were sorted and examined under the microscope. Findings of the study showed that Thrips hawaiiensis (Morgan), (Thripidae: Thripinae) was the only species of thrips infesting “Magallanes” pummelo. This constitutes the first report in this …

Efficacy Study Of Selected Maize (Zea Mays L.) Genotypes Against The Asian Corn Borer, Ostrinia Furnacalis (Guenée), Yoryncita Marfori, Merdelyn Caasi-Lit, Tonette Laude

The Philippine Agricultural Scientist

Laboratory and screen house studies were conducted to assess the efficacy of selected twenty-six maize varieties against Asian corn borer (ACB), Ostrinia furnacalis (Guenée). Hierarchical tree based on resistance parameters clearly revealed that the twenty-six maize varieties are best classified into three groups, viz. resistant, intermediate, and susceptible. In laboratory test, the varieties RCS2, RCS4, RCS5, 'IPB Var13', Bt2, Bt3, and Bt4 were consistently identified as highly resistant. Further examinations in stalk feeding assay showed that the resistant varieties had sharp decline in larval survival (LS) on the 2^nd to the 5^th day of larval feeding in …

The Influence Of Singlet Oxygen And Loss Of Function Of Fatty Acid Desaturase 7 In The Chloroplast On Aphid Resistance In Arabidopsis Thaliana, Hillary Donna Fischer

Graduate Theses and Dissertations

Fatty Acid Desaturase 7 (FAD7) is a chloroplast-localized enzyme that alters the fatty acid content of photosynthetic membranes, and that negatively regulates plant defenses against aphids. Previous studies in the model organism Arabidopsis (Arabidopsis thaliana) have shown that loss-of-function mutations in FAD7 decrease population growth of the green peach aphid (GPA; Myzus persicae Sulzer). This study further characterized the effects of a fad7 null mutant on aphids, and investigated the role of reactive oxygen species (ROS), including singlet oxygen (1O2), in plant responses to aphid resistance in fad7 as well as in wild type plants and a mutant with heightened …

Maximum Entropy (Maxent) Modeling Of The Potential Distribution Of Aspidiotus Rigidus Reyne (Hemiptera: Diaspididae) In The Philippines, Ireneo B. Pangga, Sheryl A. Yap, Arnold R. Salvacion

The Philippine Agricultural Scientist

The coconut scale insect (CSI) Aspidiotus rigidus Reyne (Hemiptera: Diaspididae) poses a significant threat to coconut production in the Philippines as shown by recent outbreaks. Ecological niche modeling using Maximum Entropy (MaxEnt) was used to determine the effects of environmental factors on the infestation of A. rigidus, and map its potential distribution in the Philippines to assess the risk of future outbreaks. The influence of bioclimatic variables on A. rigidus infestation was determined using MaxEnt modeling using the location data of A. rigidus occurrence confirmed using molecular markers. Rainfall and temperature variables were important for A. rigidus distribution with …

High Plains Wheat Mosaic Virus: An Enigmatic Disease Of Wheat And Corn Causing The High Plains Disease, Satyanarayana Tatineni, Gary Hein

Department of Entomology: Faculty Publications

Brief history: In 1993, severe mosaic and necrosis symptoms were observed on corn (maize) and wheat from several Great Plains states of the USA. Based on the geographical location of infections, the disease was named High Plains disease and the causal agent was tentatively named High Plains virus. Subsequently, researchers renamed this virus as maize red stripe virus and wheat mosaic virus to represent the host and symptom phenotype of the virus. After sequencing the genome of the pathogen, the causal agent of High Plains disease was officially named as High Plains wheat mosaic virus. Hence, High Plains virus, …

Arthropod Resistant Tomatoes: Screening Tools, Yield And Nutritional Quality Of Interspecific Hybrids, Mohammad Hasan Salman Ali Dawood

Theses and Dissertations--Plant and Soil Sciences

Tomato (Solanum lycopersicum) is one of the most economically important vegetable crops grown around globe but is a host for numerous pests and pathogens. In the future, tomato breeders will have to focus on increasing fruit quantity and on enhancing pest resistance. Many accessions of the wild relative of tomato, S. habrochaites display high levels of resistance towards arthropods such as spider mites. The presence of the sesquiterpene hydrocarbon, 7-epi-zingiberene, found in S. habrochaites type IV trichomes has been associated with arthropod resistance. However, the presence of other compounds in its trichome secretions may also be related …

Neonicotinoid Seed Treatments Of Soybean Provide Negligible Benefits To Us Farmers, Spyridon Mourtzinis, Christian H. Krupke, Paul D. Esker, Adam J. Varenhorst, Nicholas J. Arneson, Carl A. Bradley, Adam M. Byrne, Martin I. Chilvers, Loren Giesler, Ames Herbert, Yuba R. Kandel, Maciej J. Kazula, Catherine Hunt, Laura E. Lindsey, Sean Malone, Daren S. Mueller, Seth Naeve, Emerson Nafziger, Dominic D. Reisig, William J. Ross, Devon R. Rossman, Sally Taylor, Shawn P. Conley

Department of Plant Pathology: Faculty Publications

Neonicotinoids are the most widely used insecticides worldwide and are typically deployed as seed treatments (hereafter NST) in many grain and oilseed crops, including soybeans. However, there is a surprising dearth of information regarding NST effectiveness in increasing soybean seed yield, and most published data suggest weak, or inconsistent yield benefit. The US is the key soybean-producing nation worldwide and this work includes soybean yield data from 194 randomized and replicated field studies conducted specifically to evaluate the effect of NSTs on soybean seed yield at sites within 14 states from 2006 through 2017. Here we show that across the …

Dual Biological Control: Characterization Of Fungi And Bacteria To Control Granary Weevil And Fungal Pathogens Of Stored Grain, Gülçin Ercan

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Cereals are main food sources for humans and animals. However, during storage, cereal grains can be infested by insects and fungi. One of the most important insect storage pests is Sitophilus granarius (L., Coleoptera: Curculionidae). Adults and larvae can cause serious grain losses. In addition to insect pests, fungal pathogens may also invade the grain and cause economic loss, including contamination with mycotoxins, which threaten mammal health by causing serious disease. The most common mycotoxigenic grain fungi are species that belong to the genera Fusarium, Aspergillus and Penicillium. Currently, the most commonly used management strategies for insect and …

The Impact Of Fall Armyworm, Spodoptera Frugiperda (J.E. Smith), Feeding And Mechanical Defoliation On Growth And Yield Of Rice, Oryza Sativa (L.), Layton Denman Mccullars

Graduate Theses and Dissertations

The fall armyworm, Spodoptera frugiperda (J.E. Smith), (FAW) is a serious pests of many crops, and can be observed feeding throughout the entire growing season on rice, Oryza sativa, (L.). A new defoliation based threshold would help rice growers and consultants make more economically sound decisions for FAW. Work from this thesis focuses on determining the amount of damage caused by FAW feeding at different growth stages and effective insecticide seed treatments for controlling this pest.

Field plots were mechanically defoliated to determine grain yield loss across multiple growth stages and defoliation percentages. Results indicated that defoliation in late vegetative …

The Tripartite Interaction Between Arbuscular Mycorrhizal Fungi, Rice, And Insects, Lina Bernaola Alvarado

LSU Doctoral Dissertations

Losses caused by pests remain an important limitation to achieving high rice yields in the United States. Arbuscular mycorrhizal fungi (AM fungi) are able to modify plant physiology by increasing plant growth or inducing defense responses against insect herbivores. However, studies of the role of AM fungi in agroecological factors, including natural occurrence, plant resistance, soil dependency, and plant tolerance, with specific regards to pests that feed on rice plants have not been conducted before. A three-year study revealed natural occurring colonization by AM fungi on rice roots sampled in four rice-producing areas in the southern United States. Overall, rice-AM …

Global Responses Of Resistant And Susceptible Sorghum (Sorghum Bicolor) To Sugarcane Aphid (Melanaphis Sacchari), Hannah M. Tetreault, Sajjan Grover, Erin Scully, Tammy Gries, Nathan A. Palmer, Gautam Sarath, Joe Louis, Scott E. Sattler

Department of Entomology: Faculty Publications

The sugarcane aphid (Melanaphis sacchari) has emerged as a significant pest for sorghum. The use of sugarcane aphid-resistant sorghum germplasm with integrated pest management strategies appears to be an excellent solution to this problem. In this study, a resistant line (RTx2783) and a susceptible line (A/BCK60) were used to characterize the differences in plant responses to the sugarcane aphid through a series of experiments, which examined global sorghum gene expression, aphid feeding behavior and inheritance of aphid resistance. The global transcriptomic responses to sugarcane aphids in resistant and susceptible plants were identified using RNA-seq and compared to the …

Evaluation Of Rice Stink Bug, Oebalus Pugnax (F.), Damage And Monitoring Techniques In Rice, Oryza Sativa L., And Grain Sorghum, Sorghum Bicolor (L.), Aaron Joseph Cato

Graduate Theses and Dissertations

Rice stink bug, Oebalus pugnax (F.), is a serious pest of headed rice, Oryza sativa L. and an occasional pest of heading grain sorghum in the Mid-south. Work from this dissertation focuses on resolving gaps in and knowledge of rice stink bug sampling and management, and attempts to create a basis for rice stink bug damage assessment in future studies.

Field experiments were conducted from 2016-2018 to asses variation in sweep net sampling by observing producers, researchers, extension personnel, consultants and their workers. Large levels of variation were found in sweep lengths between observed sweepers and reliability of smaller sweep …

Impact Of Roadside Maintenance Practices On Larinus Minutus (Gyllenhal), A Biological Control Agent Of Spotted Knapweed, Mary Elizabeth Ferguson

Graduate Theses and Dissertations

Spotted knapweed, Centaurea stoebe, is an invasive weed found throughout much of the United States. Spotted knapweed is a rangeland weed where it was originally introduced into western North America in the 1880s.Where spotted knapweed spread to the southeastern U.S., it is found mostly along roadsides. It has been the focus of a biological control program beginning in the 1960s, with 12 insects established, with the final introductions occurring in the 1990s. After the success observed in the western U.S. and Canada with one of these insects, Larinus minutus, this weevil was established in northwestern Arkansas. It is too early …

Seasonal Phenology, Distribution And Treatments For Polyphagotarsonemus Latus (Banks) On Primocane-Fruiting Blackberries (Rubus L. Subgenus Rubus) In Arkansas, Jessica Anne Lefors

Graduate Theses and Dissertations

Worldwide, blackberries (Rubus L. subgenus Rubus) are an economically important crop. In 2007, Polyphagotarsonemus latus (Banks) (broad mites), were first reported damaging primocane-fruiting blackberries in Fayetteville, Arkansas. Since this time, broad mite damage to blackberries and yield loss has been reported in many states and countries. Despite the increasing reports of this blackberry pest, little is known about their population dynamics, and few treatments are available. Growers with broad mite populations need a pest management program to minimize yield loss. Therefore, there was a need to develop sampling techniques, describe broad mite seasonal phenology in blackberry fields, and determine efficacy …

Horizontal Transmission Of Helicoverpa Armigera Nucleopolyhedrovirus (Hearnpv) In Soybean Fields Infested With Helicoverpa Zea (Boddie), Joseph Lee Black

Graduate Theses and Dissertations

Helicoverpa armigera Nucleopolyhedrovirus (HearNPV) is a commercially available viral biopesticide that targets Heliothines, including Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), the most damaging pest of soybean (Glycine max (L.) Merrill) in the Mid-South. Previous formulations of HearNPV have been well studied; however, no research has been published on current formulations. The first objective of this thesis was to assess the rate of horizontal transmission of HearNPV in a soybean field infested with H. zea when HearNPV was applied as a bio-insecticide, and to identify arthropods that are important obligate carriers in dissemination. HearNPV spread 200 feet in 3 fields, and was …

Seasonality And Management Of Spotted Wing Drosophila On Berry Crops And Wild Hosts In Arkansas, Lizabeth Rubi Herrera

Graduate Theses and Dissertations

Spotted wing drosophila (SWD), Drosophila suzukii (Matsumura) is a serious invasive pest of small fruit production in North and South America and Europe since 2008. The primary control method is to apply insecticides every 5-7 days. Therefore, it is necessary to develop control tactics that are less chemical dependent to enhance an integrated approach for SWD management. The objectives of this study were to monitor SWD populations in different crop systems and adjacent landscape habitats; identify wild hosts of SWD; evaluate the effectiveness of insect exclusion netting in tunnels to prevent blackberry and blueberry infestations, and compare effects of netted …

Swainsonine Biosynthesis Genes In Diverse Symbiotic And Pathogenic Fungi, Daniel Cook, Bruno G. G. Donzelli, Rebecca Creamer, Deana L. Baucom, Dale R. Gardner, Juan Pan, Neil Moore, Stuart B. Krasnoff, Jerzy W. Jaromczyk, Christopher L. Schardl

Plant Pathology Faculty Publications

Swainsonine—a cytotoxic fungal alkaloid and a potential cancer therapy drug—is produced by the insect pathogen and plant symbiont Metarhizium robertsii, the clover pathogen Slafractonia leguminicola, locoweed symbionts belonging to Alternaria sect. Undifilum, and a recently discovered morning glory symbiont belonging to order Chaetothyriales. Genome sequence analyses revealed that these fungi share orthologous gene clusters, designated “SWN,” which included a multifunctional swnKgene comprising predicted adenylylation and acyltransferase domains with their associated thiolation domains, a β-ketoacyl synthase domain, and two reductase domains. The role of swnK was demonstrated by inactivating it in M. robertsii through homologous …

Over-Summering Ecology Of The Wheat Curl Mite (Aceria Tosichella Keifer), Anthony J. Mcmechan

Department of Entomology: Dissertations, Theses, and Student Research

The wheat-mite-virus complex is a consistent and significant threat to winter wheat production in the western Great Plains. This complex consists of three viruses (Wheat streak mosaic virus, Triticum mosaic virus, and Wheat mosaic virus that are transmitted by the wheat curl mite (Aceria tosichella Keifer). Yield impacts from this complex are typically associated with the presence of volunteer wheat that emerges prior to harvest as a result of hail occurring during the heading stages of wheat in early summer. Historical literature on pre-harvest germination has been primarily focused on accelerating breeding programs; however, critical gaps in knowledge exist on …

Exploration Of Chemical And Biological Management Strategies For Diaphorina Citri The Primary Vector Of Candidatus Liberibacter Asiaticus, Gretta Marie Sharp

Biology Theses

Diaphorina citri (Hemipteran: Psyllidae), the Asian citrus psyllid, is a phloem-feeding, invasive species endemic to southern Asia that was first identified in the United States in Florida in 1998. Since introduction, D. citri has spread across the major citrus growing regions of the United States. This is of great concern to the citrus industry because D. citri is the primary vector of Candidatus Liberibacter asiaticus the causal agent of Haunglongbing (HLB). Haunglongbing is the most economically devastating disease of citrus causing an estimated 8.92 billion dollars lost in revenue and 4.62 billion dollars lost in gross domestic product between 2006-2007 …

A Brief History Of Corn: Looking Back To Move Forward, Jon Derek Pruitt

Doctor of Plant Health Program: Dissertations and Student Research

Maize was domesticated from teosinte in Mexico some 7,000 to 10,000 years ago and quickly spread through the Americas. It has become one of the most important crops at a local and global level. Two types, Northern Flint corn and Southern Dent corns provided the basis of the genetic background of modern maize hybrids. The development of hybrids, first double-cross and later single-cross hybrids, along with a transition to high input farming provided huge yield increases, which have continued to improve with improving technology.

Increase in maize production also caused a rise in Western corn Rootworm (Diabrotica virgifera virgifera …

Managing Drought Stress In California Agricultural Systems, Gregory D. Brittain Jr.

Doctor of Plant Health Program: Dissertations and Student Research

California is currently facing a historic drought, and this has led many farmers in the state to severely cut back on irrigation. Optimal use of water for irrigation requires a comprehensive understanding of how plants respond physiologically to water stress (Chapter 1). By monitoring water requirements in crops and managing irrigation to meet those requirements, growers can significantly reduce water use (Chapter 2). This can be done through improving application efficiency of irrigation technology as well as increasing the water use efficiency of the crops themselves. Deficit irrigation practices can be used to manipulate the physiology of water use in …

Ecological Risks Of The Conventional Insecticide/Fungicide Seed Treatment Mixture Of Thiamethoxam And Mefenoxam In Soybean On Beneficial Insects, Carolina Camargo

Department of Entomology: Dissertations, Theses, and Student Research

The impact of neonicotinoid seed treatments on beneficial insects has been a controversial topic during the last years. While neonicotinoids are usually used as mixtures with systemic fungicides, few studies have examined the impact of the mixtures on beneficial insects. Pesticide mixtures can have synergistic, additive, or antagonistic effects on the toxicity of neonicotinoids on non-target species.

Thiamethoxam with mefenoxam is the most used neonicotinoid insecticide/fungicide mixture applied to soybean. Based on the systemic nature of thiamethoxam and mefenoxam, residues of this insecticide/fungicide mixture can be present in soybean vegetative and floral tissue with potential impacts to beneficial insects. This …

A Comparative Study Of Medicago Truncatula Transcriptomes As They Relate To Saponin Defenses Against Insect Pests, Audra Mae Rogers

Graduate Theses and Dissertations

Triterpene saponins are a class of defensive plant-derived compounds, which have a

variety of functions including antimicrobial, insecticidal, and nematicidal activities. This

research assessed the performance of the beet armyworm, Spodoptera exigua, following ad

libero feeding on Medicago truncatula accessions differing in specialized metabolite and

saponin profiles. Insect performance did not directly relate to the foliar saponin levels in the

accessions, which was measured using HPLC mass spectrometry. Accession ESP105 had the lowest foliar saponins overall, yet had similar levels of soyasaponins compared to the other accessions. Conversely, accessions A17, PRT178, and GRC43 had high foliar saponins with particularly high …

Canola: A Modern Crop For A Modern Era, Kenneth J. Roché

Doctor of Plant Health Program: Dissertations and Student Research

The University of Nebraska-Lincoln Doctor of Plant Health program is a professional doctorate program with a comprehensive approach to plants and agriculture. The program emphasizes a broad interdisciplinary education across all plant-related disciplines, practical learning, research, and experience through internships. For my final required internship, I worked as a senior agricultural research intern with Research Designed for Agriculture (RD4AG) in Montana. RD4AG is a contract research organization based in Yuma, AZ with over thirty-years of experience. During my three month internship at RD4AG in Montana, a large portion of my responsibilities centered on managing regulated canola trials that were undertaken …

Seasonal Activity And Sampling Methods For The Dectes Stem Borer, Dectes Texanus Leconte, In Nebraska Soybeans, Zachary D. Rystrom

Department of Entomology: Dissertations, Theses, and Student Research

The Dectes stem borer, Dectes texanus Leconte, has caused significant economic damage to soybean fields in south central Nebraska during recent years. Most economic injury occurs when soybean plants become susceptible to late season lodging due to larval girdling. Developing a comprehensive management plan for Dectes stem borer in Nebraska is limited by lack of knowledge of seasonal activity and effective sampling plans to monitor adult populations. Field studies were conducted in 2013 and 2014 to describe Dectes stem borer adult emergence patterns, female ovipositional period and adult densities in soybean fields. Calendar date predictions for adult emergence varied, while …