Fundamental Principles of Plant Pathology for Agricultural Producers

All crop plants produced in Kentucky have the potential to become diseased under certain conditions. Diseases of crops can affect yield and/or quality of the harvested commodity. This can impact profitability and increase the risks of farming. A plant is diseased when it is affected by some agent that interferes with its normal development. Some disorders are caused by noninfectious factors, such as temperature extremes or nutrient deficiencies. However, this publication focuses on diseases caused by infectious microorganisms. Diseased plants exhibit a variety of symptoms. These can include stunting, yellowing, wilting, twisting, reddening, browning, blighting, root rot, fruit rot, or other abnormalities. Accurate diagnosis is important in order to effectively control a plant disease. Diagnosis is an art as well as a science, and experience is important. Until a disease is properly diagnosed, a farmer may waste time and money trying to correct a problem with an unknown cause. Once a disease is diagnosed, appropriate control practices can be selected. Your local Extension agent can provide information on identification and management of crop diseases

Managing Alfalfa Diseases

Diseases of alfalfa can limit productivity of this valuable forage crop. Alfalfa diseases can reduce forage yield, reduce forage quality, and decrease stand persistence. The effects of diseases can be dramatic, such as sudden stand loss due to Sclerotinia crown and stem rot. Often, the effects of alfalfa diseases are more subtle but are no less important. For example, alfalfa plants with Phytophthora root rot sometimes regrow slowly after cutting, resulting in a stunted stand showing no other obvious symptoms of disease. Like most crop diseases, alfalfa diseases are most effectively managed by integrating as many control measures as practical. This report will provide an overview of several timely topics relative to alfalfa disease management

Kentucky Plant Disease Management Guide for Forage Legumes

This guide contains information on the biology and management of the most important diseases of forage legumes in Kentucky. Fundamental information on symptoms, disease cycle, and management is provided. For some diseases, more extensive information on biology and management is also available in other Extension publications. Additional sources of information are listed under individual diseases. Disease management in forage legumes relies heavily on using disease-resistant varieties and employing sound agronomic practices. It is important to integrate both of these strategies into a comprehensive disease management program. Failure to consider one or the other will compromise the success of your efforts. The appropriate use of pesticides sometimes plays a significant role in managing certain diseases, but it is secondary to sound cultural practices and proper variety selection. Resistance to one or more diseases is often incorporated into modern crop varieties. Unfortunately, resistance is not available for some diseases. However, when available, disease resistance is often the foundation for economical disease control

A Solution to Some Spring-Seeded Alfalfa Problems

One of the most important assignments I received when I assumed this position in 1990 was to address the question, What is the cause of seeding failure when alfalfa is spring-seeded into soils that remain wet after seeding? Six years of laboratory and field work have finally borne fruit. Based on our research, we can confidently present Kentucky alfalfa producers with three conclusions and a recommendation

Genetically Engineered Crops: Emerging Opportunities

Biotechnology is “any technological application that uses biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use.” This definition encompasses many, many applications, including traditional ones such as fermentation of alcoholic beverages. In certain biotech crops, their genetic material (DNA) has been purposefully manipulated in the laboratory. These genetically engineered crops are often called “GMOs,” an acronym for “genetically modified organisms.” These GMOs are the focus of this publication

Fundamental Principles of Plant Pathology for Agricultural Producers [2015]

All crop plants produced in Kentucky have the potential to become diseased under certain conditions. Diseases of crops can affect yield and/or quality of the harvested commodity, which can impact profitability and increase the risks of farming

Is Ridomil Recommended When Seeding Alfalfa?

Ridomil 2E® fungicide received a federal label in 1991 for control of seedling diseases of alfalfa caused by Pythium and Phytophthora fungi. Pythium fungi are widespread in Kentucky soils but can be controlled with Apron® seed treatment. Phytophthora is less common in Kentucky soils. Where present, Phytophthora can usually be controlled with a combination of resistant varieties and Apron seed treatment. Occasionally, yield increases may be observed using Ridomil in fields highly infested with Phytophthora. However, broadcast applications of Ridomil at seeding are not recommended for most alfalfa fields in Kentucky

Alfalfa Disease Management

Alfalfa can be a vigorous and productive forage crop for Kentucky farmers. Like all farm crops, however, alfalfa is subject to infectious diseases that can limit forage production. Managing these diseases is an important part of economical alfalfa production

Progress towards Sclerotinia--Resistant Varieties

Sclerotinia crown and stem rot (SCSR), caused by the fungus Sclerotinia trifoliorum, is one of the most important factors limiting the success of late-summer alfalfa seedings in the region. Infections of S. trifoliorum that progress into the crown of a fall-sown alfalfa plant can kill it during winter or spring green up. Stand losses by the following spring may be insignificant (1-3%) or nearly total, with 95-99% of the stand being dead (and often even rotted away and gone by spring green-up)

Managing Spring Dead Spot of Bermudagrass

Spring dead spot is the most destructive disease of bermudagrass in Kentucky. The most serious outbreaks occur under high maintenance conditions; e.g., high nitrogen fertility, low mowing height, and frequent traffic. Moderate to severe outbreaks can occur under low-maintenance conditions as well. High levels of resistance to spring dead spot in bermudagrass varieties have not yet been demonstrated experimentally. Limited data suggest that those varieties with best winter hardiness are somewhat less susceptible to the disease. To date, no confirmed cases of spring dead spot have been documented in “Quickstand” bermudagrass, which may indicate that this variety will suffer less from the disease than other available varieties