Education Commons^™

Breeding For Resistance In California Strawberry To Verticillium Dahliae, Zachary Christman

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

This article focuses on breeding resistant strawberries to the fungus Verticillium dahliae, common name Verticillium wilt. This is a serious fungal disease that can result in a loss of 50% or more of a strawberry harvest when grown in infested soil. The main goal is to provide an example of how a cultivar can be made more resistant to a plant pathogen with the use of plant breeding methods.

Since 1930 the University of California, Davis, has been developing strawberry cultivars that are adapted to the agricultural industry and regional farms. Developing cultivars that require fewer inputs are of …

Nf04-614 Management Program For Powdery Mildew Of Wheat (Revised August 2005), John E. Watkins

University of Nebraska-Lincoln Extension: Historical Materials

This NebFact, Wheat Disease Fact Sheet No. 7, discusses the management program for powdery mildew of wheat. It covers the cause and occurrence, key symptoms, cultural management practices, fungicide treatment programs with a table listing the fungicdes registered for foliar diseases of wheat, and application.

G1507 Summer Patch And Necrotic Ring Spot, John E. Watkins

University of Nebraska-Lincoln Extension: Historical Materials

This NebGuide describes the causes, predisposing conditions, and symptoms of summer patch and necrotic ring spot, and provides recommendations for their control.

Introduction

Two of the most destructive turfgrass patch diseases are summer patch and necrotic ring spot, both of which are present in Nebraska. The symptoms of necrotic ring spot and summer patch are essentially identical, making it difficult to distinguish the two apart in an affected turf. If the symptoms begin in May, necrotic ring spot is probably the cause; if they begin in July and August, then summer patch is suspect. In Nebraska summer patch is probably …

G03-1522 Damping Off Of Seedlings And Transplants, Laurie Hodges

University of Nebraska-Lincoln Extension: Historical Materials

The shift toward more ecological means of pest control is a driving force in research and in growers' fields. Growers need to understand how the various pathogens causing plant disease respond to environmental conditions and cultural practices — what keeps the level of disease below an economic threshold and how these conditions can be developed and maintained for more sustainable production.

This NebGuide provides information on two common pathogens that cause seedling disease (damping off) in many crops. Although vegetable production is used in the examples, the principles apply to many cropping systems.

Nf00-411 Seed Treatment Fungicides For Soybeans (Revised January 2004), Loren J. Giesler

University of Nebraska-Lincoln Extension: Historical Materials

The most common soybean disease problem in Nebraska is seedling damping off and seed rot caused by several fungi. Early season damping off and root rots are often followed by premature death, which in many instances may be attributed to fungal infections earlier in the season.

This NebFact discusses the seed treatment fungicides for soybeans. These includes protectants (contacts) that are effective only on the seed surface; and systemic fungicides that are absorbed by the emerging seedling, which inhibit or kill the fungus inside host plant tissues.

Nf99-397 Gray Leaf Spot Of Perennial Ryegrass In Nebraska, John E. Watkins

University of Nebraska-Lincoln Extension: Historical Materials

Gray leaf spot, caused by the fungus Pyricularia grisea, was reported in the early 1970s to be a damaging disease of annual ryegrass grown for forage in the southeastern United States. Forage yield losses were so severe that the disease was named ryegrass blast.

This NebFact discusses the diagnosis, future occurrences, and management of gray leaf spot in Nebraska and surrounding states.

G97-1330 Apple Scab, Diane A. Merrell, Donald Steinegger

University of Nebraska-Lincoln Extension: Historical Materials

Apple scab, caused by the fungus Venturia inaequallis, occurs worldwide wherever apples are grown. Scab is one of the most important diseases of apples and crabapples in Nebraska.

This NebGuide discusses the apple scab disease, its symptoms, disease cycle, and cultural and chemical control. Varieties of apples and crabapples are listed according to their degree of resistance.

G97-1327 Cedar-Apple And Related Rusts Of Apple And Ornamentals, Don Steinegger, Jane A. Christensen

University of Nebraska-Lincoln Extension: Historical Materials

Discussion of complex inter-species disease life cycle in junipers and apple trees, description of symptoms, control measures, and lists of varieties of species resistant to cedar-apple rust and related rusts.

Cedar-apple rust is a disease that causes substantial injury to apple and crabapple trees in Nebraska. The disease is caused by the fungus Gymnosporangium juniperi-virginianae and occurs wherever apples and junipers are grown in close proximity.

Nf96-301 Gray Leaf Spot In Corn, David S. Wysong

University of Nebraska-Lincoln Extension: Historical Materials

This NebFact has information on ways to manage gray leaf spot in Corn.

G95-1250 Rust Of Dry Bean, James R. Steadman, H. F. Schwartz, Dale T. Lindgren

University of Nebraska-Lincoln Extension: Historical Materials

The symptoms, sources, spread and management of rust in dry edible beans is discussed in this NebGuide.

Rust is an important disease that affects dry beans in eastern Colorado, western Nebraska and adjacent regions. The disease is caused by the fungus Uromyces appendiculatus which has caused periodic epidemics in this region since the 1950s. Recent yield losses from the disease have exceeded 50 percent in some areas.

G95-1264 Storing Fresh Fruits And Vegetables, Susan D. Schoneweis, Durward Smith

University of Nebraska-Lincoln Extension: Historical Materials

The following NebGuide outlines proper storage methods and conditions for fresh fruits and vegetables.

Harvesting fruits and vegetables from your garden at the proper stage of maturity is only the first step to fresh table quality. Proper harvesting and post-harvest handling methods, as well as proper storage of fruits and vegetables not immediately eaten, will help maintain the flavor, texture and nutritive value of the produce.

Proper storage means controlling both the temperature and relative humidity of the storage area. All fruits and vegetables do not have the same requirements. This NebGuide will help you select the best storage conditions …

G95-1270 Sclerotinia Stem Rot Of Soybeans, James R. Steadman, S. Rutledge, D. Merrell, David Wysong

University of Nebraska-Lincoln Extension: Historical Materials

Life cycle, symptoms, and control measures of sclerotinia stem rot of soybeans is discussed.

Sclerotinia stem rot of soybeans is caused by the fungus Sclerotinia sclerotiorum. This pathogen has an extremely wide host range and can affect more than 400 plant species, including oilseed, vegetable and forage legume crops. S. sclerotiorum has caused a disease known as white mold on dry edible beans in western Nebraska for 40 years, but it did not become a problem in soybeans until the 1990s. This fungal pathogen can be found on soybeans in Illinois, Iowa, Michigan, Ohio, Minnesota, Wisconsin, and North Dakota. …

G94-1200 Anthracnose Diseases Of Shade Trees (Revised July 1997), Laurie J. Stepanek, Mark O. Harrell, David S. Wysong

University of Nebraska-Lincoln Extension: Historical Materials

This NebGuide describes anthracnose diseases in sycamore, ash, oak, maple and walnut trees and offers suggestions for control.

Anthracnose diseases affect a wide variety of plants including many popular shade trees. Sycamore, ash, oak, maple, and walnut commonly exhibit symptoms each spring. Although the symptoms may appear serious, anthracnose diseases rarely kill trees. In most cases, healthy trees quickly recover from anthracnose infections with little damage to their long-term health.

G93-1149 Stripe Smut Disease Of Turfgrass, John E. Watkins, Roch E. Gaussoin

University of Nebraska-Lincoln Extension: Historical Materials

Ways to identify and treat smut fungi are given here.

Smut fungi infect various grasses, either cultivated or found naturally in the wild. In turfgrass, one of the most common smut diseases is stripe smut caused by Ustilago striiformis.

Stripe smut occurs most commonly on Kentucky bluegrass, occasionally on bentgrass and rarely on fine fescues and perennial ryegrass; it has not been reported to occur on zoysia. The widespread use of susceptible Kentucky bluegrass cultivars has contributed to the common occurrence of stripe smut.

Stripe smut should not be taken lightly by turfgrass managers. Infection causes a general decline, …

G92-1103 White Mold Of Dry Beans, James R. Steadman, Howard F. Schwartz, Eric D. Kerr

University of Nebraska-Lincoln Extension: Historical Materials

White mold symptoms, infection and control are covered here.

One of the most important diseases affecting dry beans in western Nebraska and Colorado is white mold caused by the fungus Sclerotinia sclerotiorum. In a recent year, losses from this disease averaged as high as 20 percent, with a few individual field losses exceeding 65 percent.

G92-1090 Black Dot Disease Of Potato, Alexander D. Pavlista, Eric D. Kerr, Robert B. O'Keefe

University of Nebraska-Lincoln Extension: Historical Materials

The cause, symptom, disease cycle, influencing factors, effects and control of black dot are described. Black dot of potato, a disease caused by the fungus Colletotrichum coccodes, was recognized in Australia and Europe, then was observed and described in Canada in 1921. Since then this disease has spread to many potato production areas of the United States; its occurrence was first reported in Nebraska in 1988. In the past few years, black dot has been recognized on infected potato tissue from several areas of the state. The increased incidence of black dot in Nebraska may have been favored by high …

G91-1060 Black Spot Of Roses, John E. Watkins

University of Nebraska-Lincoln Extension: Historical Materials

Black spot, Nebraska's most troublesome rose disease, can be controlled through selection of a resistant cultivar, spaced plantings, and an active fungicide spray program.

Roses are one of the most versatile and inspiring ornamentals for landscaping. There are roses adapted for any garden site and landscape purpose. Roses are not always easy to grow and may require a little more management than other ornamentals. One of the greatest challenges to successfully growing garden roses is disease control.

Nf91-29 Ringworm And Club Lamb Fungus, Doyle Wolverton, Ted Doane

University of Nebraska-Lincoln Extension: Historical Materials

Sheep exhibitors, as you prepare for summer shows, examine how you prepare your sheep for the show ring. Washing and shearing removes the natural lanolin and suint that protects sheep from getting some diseases. Anyone who shows sheep this summer should be aware of ringworm and a ringworm-like disease that can be transmitted from infected sheep to humans. One ringworm type disease, caused by a fungus, is currently being called "club lamb" fungus.

G90-979 Powdery Mildew Of Roses, John E. Watkins

University of Nebraska-Lincoln Extension: Historical Materials

Cause, symptoms of and conditions for powdery mildew are covered, as well as ways to control the disease.

The rose is one of the most popular flowering ornamentals in the world. It is thought to have first been cultivated 4,000 to 5,000 years ago in northern Africa. Today it is a favorite ornamental for landscapes, as well as the most important commercial cut flower.

G90-970 Summer Patch And Necrotic Ring Spot, John E. Watkins, Robert C. Shearman, Terrance P. Riordan

University of Nebraska-Lincoln Extension: Historical Materials

This NebGuide describes the causes, predisposing conditions, and symptoms of summer patch and necrotic ring spot, and provides recommendations for their control.

Research since 1980 has resulted in considerable progress in identifying causes of the "patch"-type disease of turfgrass. Two of the most destructive patch diseases of turfgrasses are summer patch and necrotic ring spot.

Both summer patch and necrotic ring spot are present in Nebraska turfs. Unfortunately, necrotic ring spot and summer patch cause identical symptoms and cannot be distinguished in the field, and identification in the laboratory is time-consuming (3-6 months) and laborious.

G90-980 Rose Mosaic And Rose Rosette Diseases, John E. Watkins

University of Nebraska-Lincoln Extension: Historical Materials

The rose mosaic and rose rosette diseases may cause a variety of symptoms, including reduced plant vigor and flower quality. Early detection is essential to control.

Roses have been cultivated as an ornamental for 4,000 to 5,000 years and now are distributed worldwide. Rose virus and virus-like diseases occur wherever roses are grown. Since roses are vegetatively-propagated through budding or grafting, these pathogenic agents are easily spread during propagation. Infection by virus or virus-like agents may cause a wide variety of symptoms. These can range from latent, symptomless infections to mosaic leaf patterns and distortions, severely distorted canes, and finally, …

G89-951 Mushrooms, Puffballs, Fairy Rings, And Slime Molds In Turfgrass, John E. Watkins

University of Nebraska-Lincoln Extension: Historical Materials

How do you identify -- and treat -- mushrooms, puffballs, fairy rings and slime molds? Read on.

Some mushrooms and most puffballs are edible; some are foul-smelling, many are considered unsightly, and a few are poisonous; but when they appear on a lawn, most are considered a nuisance.

G88-890 Pythium Blight Of Turfgrass, John E. Watkins, Robert C. Shearman

University of Nebraska-Lincoln Extension: Historical Materials

Causes, symptoms and treatment for pythium blight are covered here.

Pythium blight, sometimes called "grease spot" or "cottony blight," is no longer a disease of golf courses; it also is a serious problem in home lawns and other turfs. Caused by several species of Pythium fungi, the two most commonly associated with Pythium blight are Pythium aphanidermatum and P. graminicola. These fungi are in a group known as "the water molds," a group that includes Phytophthora and other pathogenic genera. They are referred to as "water molds" because they function best under wet, saturated soil conditions.

The Pythium species …

G86-824 Snow Mold Diseases Of Turfgrasses (Revised February 1991), John E. Watkins

University of Nebraska-Lincoln Extension: Historical Materials

How to identify, prevent, and control the principal snow molds of turfgrass in Nebraska.

Principal snow molds of Nebraska turfgrass are Fusarium patch (pink snow mold) and Typhula blight (gray snow mold). Of these two, Fusarium patch is usually the most prevalent and, due to the general lack of continuous snow cover during winter, probably the most damaging. Although snow molds occur on most types of turf grown in Nebraska, fine-leaved turf types are more often seriously injured than coarser lawn grasses.

G85-742 Dollar Spot Disease Of Turfgrass, John E. Watkins, Terrance P. Riordan

University of Nebraska-Lincoln Extension: Historical Materials

This NebGuide describes the symptoms and disease cycle of dollar spot, and provides recommendations for controlling this turfgrass disease.

Dollar spot of turfgrass is one of the most persistent diseases on golf courses in North America. All commonly grown turfgrasses in Nebraska may be attacked, but differences in susceptibility exist within cultivars of the various turf species. Presence of dollar spot in a well-managed lawn affects its aesthetic appearance and value, but usually does not threaten its survival. Lawns recover from dollar spot injury when conditions are favorable for vigorous, healthy growth.

G84-701 Septoria Leaf Blotch Of Wheat, John E. Watkins

University of Nebraska-Lincoln Extension: Historical Materials

This NebGuide describes the symptoms and disease cycle of this wheat disease, and provides recommendations for its control.

Two species of Septoria fungi infect winter wheat in Nebraska. Septoria tritici and S. avenae f. sp. triticea cause Septoria leaf blotch. This disease is also known as "Septoria tritici blotch," "Septoria leaf spot," "Septoria blotch," "Speckled leaf blotch" or as the "Septoria complex" since both Septoria species may be present in the same fields and on the same plants.

G80-488 Spring And Summer Black Stem Diseases Of Alfalfa (Revised June 1992), John E. Watkins, Fred A. Gray

University of Nebraska-Lincoln Extension: Historical Materials

Spring and summer black stem of alfalfa, their causes, symptoms, and control are discussed.

Of the two black stem diseases found in the central and northern Great Plains, spring black stem predominates summer black stem. Both are damaging when weather conditions favor their development. Although their symptoms differ, each causes spotting and darkening of stems and spotting of leaves.

G74-182 Caring For African Violets, Don Steinegger, John E. Watkins, Anne Vidaver, Frederick P. Baxendale

University of Nebraska-Lincoln Extension: Historical Materials

African violets are low, compact plants with attractive dark green, thick, hairy leaves. This NebGuide covers various aspects of caring for them.

The African violet (Saintpaulia ionantha) is one of the most satisfactory flowering houseplants. It is a low, compact plant with attractive dark green, thick, hairy leaves. The violet-like flowers are borne in small panicles just above the foliage. Besides various shades of blue-violet, there are also pink, fuschia, and white cultivars (varieties). Newer violets include not only cultivars with single flowers, but also those with semi-double or double rows of petals. Bi-colored flowers and those with …

G74-108 Wilts Of Cucurbits (Revised October 1994), James R. Steadman, David L. Keith, Laurie Hodges

University of Nebraska-Lincoln Extension: Historical Materials

Discussion covers the symptoms, disease cycles, and control measures for bacterial and Fusarium wilts of cucurbits, including cucumbers, cantaloupe, watermelons, squash, and pumpkins. Wilt caused by squash vine borer also is covered.