Date of Award:

5-1961

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Agronomy

Committee Chair(s)

D. C. Tingey

Committee

D. C. Tingey

Committee

K. R. Allred

Committee

A. H. Holmgren

Abstract

Dodder is the common name for the group of plants in the genus Cuscuta. It is a serious weed in nearly all the legume seed producing areas of southern and western United States (5). Dodder is of major economic importance in the production of alfalfa, lespedeza, clover, and of less importance in such crops as flax, onions, sugar beets, and some ornamentals.

In Millard County, which is the most important alfalfa seed producing area in Utah, growers consider dodder one of their worst threats to alfalfa seed production.

A major factor that contributes to the dodder problem in Millard County is the growing of alfalfa seed continuously on the same land. Because growing conditions in Millard County favor the production of alfalfa seed over other agronomic crops there are cases where stands of alfalfa have not been plowed for fifty years or more and during most of that period these fields produced successful alfalfa seed crops. Because dodder seed remains viable in the soil for years such practices provide for a heavy build up of dodder seeds in alfalfa seed fields. This is tending to force seed growers into shorter rotations which usually range from five to ten years. But even then most farmers prefer not to leave their fields out of alfalfa longer than two years which is not long enough to rid the soil of the dodder seeds.

No single method for dodder control has gained wide acceptance. Methods used vary. One reason for lack of confidence, in any particular control method, is that there is more than one species of dodder involved and their growth habits differ.

The purpose of this paper is to evaluate the seriousness of dodder in the production of alfalfa seed in Millard County and estimate the relative prevalence and damage caused by each species found in the area.

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