Plant Disease Basics

Disease is a natural part of every crop production system. This is true for every crop species and for each type of production system; irrigated versus rain-fed, conventional versus reduced tillage, and continuous versus rotation cropping. Consequently, in any given year, the question is not whether or not diseases will occur in Nebraska's field crops but rather which diseases will occur and at what incidence and severity.

Many factors influence disease development in plants including hybrid/variety genetics, age of the plant at the time of infection, environment (e.g., soil, climate), weather (e.g., temperature, rain, wind, hail, etc.), single versus mixed infections, and genetics of the pathogen populations. Due to variation inherent in these factors, diagnosis of plant diseases can be difficult at the early stages of disease on individual plants as well as at the early stages of an epidemic. However, for many diseases symptoms do become diagnostic at some stage of disease development and a reasonable level of confidence can be placed in diagnoses based on these symptoms.

Crop Disease List Page:

For each major crop, a crop disease list page catalogs the common diseases found in Nebraska. Each listing is a link to a crop disease page. This list is not intended to be a comprehensive catalog of all diseases that have ever occurred in Nebraska, but rather a list of the diseases one is most likely to encounter on a regular basis. Not all diseases occur in every county of Nebraska and when possible the known or projected geographic distribution of the disease will be given. Diseases will be added to each list as they become important and as resources allow.

Crop Disease Text Page:

The crop disease text page provides information in narrative and bullet statement form regarding the pathogen, disease symptoms, favorable conditions, and management. Each section has information intended to provide a basic understanding of the pathogen, the symptoms most often associated with disease development, the conditions considered favorable for disease development, and the recommended procedures for disease management. It is not a comprehensive treatment of these topics.

Image Pages:

The image page provides images of the pathogen, key symptoms associated with disease development, and signs of the pathogen when applicable. Images are accessed by link from the text page.

Disease Forecast Page:

The disease forecast page will be updated weekly to biweekly and will include information on disease occurrence and severity observed during surveys conducted in select counties. It will include information on what diseases to be on the watch for as a result of the weather for the previous 7-10 days. Links to four county pages and one South Central Ag Research Lab page are also found that provide updates on weather, crop development, and Gray Leaf Spot (GLS) development at those five locations.

Summary:

The most critical issue for profitable management of plant disease is obtaining a correct diagnosis. In any given year, the question is not whether or not diseases will occur in Nebraska's field crops but rather which diseases will occur and at what incidence and severity. Diagnosis of plant diseases can be difficult at the early stages of disease development. For many diseases, symptoms do become diagnostic and a reasonable level of confidence can be placed in diagnoses based on symptoms. To help producers, consultants, and other agricultural professionals in the diagnosis and management of field crop diseases in Nebraska, the Plant Disease Central Web Site (PDC) was developed.