Department of Plant Pathology, Physiology and Weed Science

Introduction



Profitable small grain production is attainable when care is taken to integrate practices that reduce or control the development of diseases that reduce the yield potential developed by the agronomic management practices. Each year in the humid Eastern wheat production areas of the United States, a number of diseases can and do cause significant economic loss to producers. The diseases most important to wheat producers in this area of the country are caused by a number of different fungi and viruses. Planning before planting to reduce disease incidence and severity, care taken to regularly scout your developing wheat crop for yield robbing diseases, and the timely application of appropriate disease control practices can ensure significant economic benefits.


The diseases occurring yearly within the region, and potentially the most yield limiting, can be grouped into foliar diseases, head diseases, root and crown diseases, and virus diseases.

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Disease Management Practices

Small grain diseases, although endemic, do not have to exact their toll each year from the prudent and alert wheat producer. There are a number of cultural and management practices that can be employed to significantly reduce the risk of economic loss from disease.

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Seed and Seedling Diseases

Fungicide seed treatments, properly applied, are highly recommended and can be considered inexpensive stand establishment insurance. Seed treatments minimize losses from seed decay, seedling blights, and seed- and soil-borne diseases. Slurry applications or commercial liquid applications provide the best adhesion and most uniform coverage and, thus, provide the most effective control. Recent problems with loose smut control have been attributed to poor fungicide coverage and higher levels of smut in seed that is treated. Hopper box treatments have not been providing the necessary coverage to ensure control.

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Foliar Diseases

Foliar diseases reduce photosynthetic leaf area, use nutrients, and increase respiration and transpiration within colonized host tissues. The diseased plant typically exhibits reduced vigor, growth and seed fill. Earlier occurrence, greater degree of host susceptibility, and longer duration of conditions favorable for disease development increase the yield loss.

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Head Diseases

Head diseases can cause significant losses. Seeds are replaced by the pathogen in the case of loose smut. With scab, seed may be shriveled or killed, and there is potential for mycotoxin contamination.

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Root and Crown Diseases

Root and crown diseases attack the base of the main stem and tillers. Stems and tillers that are rotted or partially rotted cannot adequately supply nutrients and water to the developing heads. As a result, heads that are produced dry up and die prematurely. They can be recognized as "whiteheads" when healthy heads are flowering.

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Virus Diseases

Viruses can only be seen with the aid of an electron microscope. They are disease-causing agents composed of nucleic acid surrounded by a protein coat. The viruses that cause disease in wheat are transmitted by insects (aphids, leafhoppers, etc.) or by root colonizing fungi. Typically, virus diseases in wheat are characterized by stunting, mosaics and/or yellowing.

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Attention

The remainder of this section is a compilation of recommended chemical disease control measures that were registered at the time of this printing. It is not intended to be an exhaustive index of all registered fungicides and nematicides. The information in this section is provided as a guide to available products but does not substitute for or supersede the information found on the pesticide label of a specific product. Trade names are included to aid in the identification of the specific active ingredient of a pesticide know to be effective. No discrimination against a similar product is intended or implied by omission. Mention of a commercial product does not constitute an endorsement by the authors or by their respective Extension services. Consult the pesticide label for any changes in rate, timing, handling orregistration. Use pesticides only as directed.


All contents copyright © by Erik L. Stromberg.
All right reserved. 1996. Any comment to E.L. Stromberg