Document Type

Thesis - Open Access

Award Date

1968

Degree Name

Master of Science (MS)

Department / School

Plant Pathology

Abstract

Stem rust, Puccinia graminis tritici Eriks. and Henn., and leaf rust, Puccinia recondita Rob. Ex Desm., destroyed an estimated 70% of the South Dakota winter wheat crop in 1962, a loss of more than 12 million bushels valued at $24 million (30). Similar losses have occurred periodically in South Dakota. Breeding programs have produced resistant varieties of spring and winter wheat; however, new races of rust have developed and attacked varieties heretofor resistant. For example, untiI 1952, the spring wheat varieties Pilot, Rival, and Mida were resistant to stem rust race 56, which had been the most prevalent race in the midwest since the 1930's. Race 15-B erupted in epiphytotic proportions destroying large acreages of these varieties and resulting in their replacement by Selkirk, a variety resistant to races 56 and 15-B. The resistance provided by Selkirk has been supplemented by resistant Crimm, Chris, and other varieties. In spite of this progress, stem rust races have been found that are capable of damaging al I of these varieties. The winter wheat varieties Omaha, Pawnee, Nebred, and Warrior were widely grown untiI 1962 when race 56 destroyed 70% of the South Dakota crop. These varieties have been replaced primarily by Hurne, Lancer, Scout, and Gage, which are resistant to the common races but, again, are susceptible to potentially destructive races. Resistance to leaf rust is less common in current varieties than is stem rust resistance; moreover, this resistance has a narrow genetic base and is even less reliable than stem rust resistance. Several investigators have found that certain fungicides control both stem and leaf rust when applied at the proper time. One primary Iimitation of chemical control is cost of application. The first part of this study is an attempt to assess the feasibility of rust control and weed control by combining fungicides with 2,4-D. To gain maximum benefit from a protective fungicide spray, the fungicide must thoroughly cover the plant where the pathogen most commonly penetrates. Foliage density, wind direction, wind velocity, and the type of applicator are factors which may affect spray deposition on wheat plants. The second part of this study is an investigation to determine the effect of foliage density on spray deposition.

Library of Congress Subject Headings

Leaf rust of wheat
Fungicides
Puccinia graminis
Wheat rusts
Rust fungi

Format

application/pdf

Publisher

South Dakota State University

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