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Shaukat Ali

Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

George W. Buchenau


Pyrenophora tritici-repentis (Died.) Drechs. (anamorph Drechslera tritici-repentis (Died.) Shoemaker), is the causal agent of tan spot, one of the important foliar diseases of wheat (Triticum aestivum L.) and many other members of the family Gramineae (Hosford,1971, Hosford and Morrall,1975, Krupinsky,1982 and 1992, Shoemaker,1962, Sprauge,1950). Losses caused by this disease have ranged from three to 50% (Hosford, 1982, Rees et al.,1982). Since the early 1980's the disease has caused serious losses in both North and South Dakota. Estimated annual yield losses in South Dakota have ranged from 5-29% (Buchenau et al.,1983). Fungicides are available to control tan spot, but there are two major constraints of using fungicides: 1) Increase in cost of production and 2) chemical pollution of the environment. Current pesticide use strategy dictates the avoidance of pesticides unless they are needed. A decision support system is needed to accurately predict when an economic threshold of disease will occur, so that wise decisions can be made about fungicide application. With some diseases, the role of weather is so predominant that a prediction system operated reasonably well on the basis of meteorological data alone. Potato late blight and apple scab are classic examples. Since the disease threshold for economic fungicide application is a function of the number of infection periods, it is important to know when such infections occur. The present studies were conducted to determine if infection periods are correctly identified by Blitecast, Epinform, or other weather-driven models such as dew degree hours (DOH) and EpinformA, and if not, to seek alternative models. In addition, an attempt was made to relate infection periods to disease progress in the field.

Library of Congress Subject Headings

Wheat -- Diseases and pests
Wheat -- Diseases and pests -- Climatic factors




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