Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Plants, Soils, and Climate

Committee Chair(s)

DeVere R. McAllister


DeVere R. McAllister


Orson S. Cannon


B. Austin Haws


Alfalfa is the most important forage crop in Utah. It is of particular importance to the Uintah Basin, Utah area where alfalfa hay and seed production are major sources of agricultural income. This crop owes much of its popularity to the fact that it will normally produce large yields of good forage on land which is unsuited to more intensive cultivation. In many cases it is impractical to advocate disease control practices which involve extra labor or expense and as a result most diseases of alfalfa, if controlled at all, are controlled by the use of resistant varieties.

During the past few years alfalfa witches' broom has become detrimental in the Uintah Basin area. This disease shortens the length of life of alfalfa stands and reduces the yield. Some diseased stands are killed out in a period of three years. It is difficult and expensive to reestablish alfalfa in this area where water supplies are usually low. Therefore, it is imperative that alfalfa stands remain in production for several years. These problems justify a study to find resistance to alfalfa witches' broom.

The objectives of this study are to select varieties of alfalfa which are resistant to alfalfa witches' broom in the Uintah Basin area, to select varieties of alfalfa which are best adapted to the area for high yield per acre, to determine which of a few insects tested are responsible for transmission of alfalfa witches' broom virus, and to determine if certain dodder species (Cuscuta spp.) act as transmission bridges for alfalfa witches' broom.