| North Dakota
Agricultural Research North Dakota State University, Fargo, ND 58105
The
History of Leafy Spurge Control in North Dakota (continued) |
Abstract |
 IntroductionLeafy spurge (Euphorbia esula L.) is a long-lived, difficult to control perennial weed with a large deep-growing root system. The recorded history of the weed in the state is also long and entangled. The story is sometimes humorous, sometimes serious to the point of despair, but always educational. To trace the history of control of this weed is to reflect on the past accomplishments and failures in noxious weed control. The farmers of North Dakota had no experience in fighting such a tenacious invader as leafy spurge. There were no statewide control plans or cooperative efforts between land owners and state or federal agencies. The knowledge gained from those experiences will help the people of the state combat future noxious weed problems more efficiently.
The first in-depth analysis of leafy spurge in North Dakota was conducted by Velva E. Rudd in 1931 and 1932 as part of her masters degree research. Her work includes a complete description of the plant, its seed production, and its spread by root (22). The detailed drawings of leafy spurge anatomy from her thesis are still in use (6). She concluded that eradication of leafy spurge from the state would be "extremely difficult" and that one should find and destroy the plant when it first appeared. Unfortunately the only control methods available at the time were cultivation for several years and sodium chlorate applied at 6 to 8 pounds per acre. Both methods prohibited cropping of the land for several years. Rudd later earned a Ph.D. in botany in 1953 from George Washington University (1). She became known world-wide as a specialist in legume taxonomy and a curator of the Botanical Herbarium at the Smithsonian Institution in Washington, D.C. Dr. Rudd moved to Reseda, California, upon "retirement" and is a senior research fellow in the department of biology at California State University-Northridge. Velva Rudd was honored as a North Dakota State University outstanding alumnae on October 7, 1994 during homecoming (Figure 1). She stated that Dr. Herbert Hanson gave her a choice of plants to study and she "had never heard of leafy spurge, so I chose that one." She did not have to travel far to do her research. The plant was growing densely in what is now near-north Fargo.
Leafy spurge had become a problem for farmers in other states before North Dakota. The date of introduction into the United States is not known, but a specimen preserved in the Torrey Herbarium of Columbia University, deposited at the New York Botanical Garden, was collected at Newbury, Massachusetts, by William Oakes in 1827 (3). He annotated the label of the plant sent to another botanist, "I want to find this at another place; have you met with it, or heard of it?" For many years it was not noted again until the first edition of Gray's Manual of Botany was published in 1848, when the author stated "it was likely to become a troublesome weed.@ Leafy spurge probably entered North America as seed from ship ballast deposited in New England and then spread west (6). It may also have been introduced into the northern Great Plains as a contaminant in oat and wheat seed. Leafy spurge was also known as 'Faitour's Grass' or 'Tithymal' (3). At first the spread of the weed was slow. It was found in New York in 1875 and in Michigan in 1881, where it was still noted as rare. However, by 1913 it was found from Michigan to New York and from New Jersey to Ontario and was considered a menace to pastures. Concern about the spread of this weed was widespread enough that the New York Herald wrote an editorial about it on February 9, 1921 (20). The writer was concerned that this weed was going to taint the milk that was shipped to New York City (Figure 2). The New York Agricultural Experiment Station pledged to a plan of eradication using such heroic methods as spreading 10 tons of crude dried salt to the acre and saturating leafy spurge patches with kerosene. It was not stated, but it is safe to assume these efforts failed.
Field bindweed (Convolvulus arvensis L.) was found in all 53 counties, while Canada thistle [Cirsium arvense (L.) Scop.] was a problem mainly in counties east of the Missouri river (23). Russian knapweed (Centaurea repens L.) was found almost exclusively in western North Dakota at about the same infestation levels as today. Perennial peppergrass [Cardaria repens (Schrenk) Jarmolenko], commonly called hoary cress today, was the other problem weed in the survey. "Control of leafy spurge and review of literature on chemical weed control" from May 1934, was the first leafy spurge control bulletin published by the Agricultural Experiment Station at NDAC (2). Chemicals discussed to control leafy spurge included sodium chloride (salt) at 2 to 13 pounds per square rod, which was a concentration "greater than that recommended for any other weed." Other compounds evaluated included sodium arsenite, calcium cyanamid and arsenic pentoxide. Chemicals applied "to leafy spurge at flowering time in early summer" gave the best results. Mid-June is still the ideal time to apply most herbicides used to control this weed. Similar advice was given in circular 55 published in June 1934 (Figure 4) (4).
A 1937 report from the LaMoure County agent explained that the county was in the fourth year of an intensive fight against leafy spurge (27). The county commissioners and 13 townships were cooperating in the spraying of 14 acres of leafy spurge with sodium chlorate (Atlacide), stated to be equivalent to 34 cultivations per year or grazing with sheep. In 1951, 14 years later, the LaMoure county agent reported they still had a leafy spurge problem, but their control program was considered quit effective. By 1996, the 14 acres had expanded to an estimated 41,000 acres and no one was all that optimistic about control (25). Chemical control recommendations remained relatively unchanged for the next two decades after initial research in the early 1930s. Sodium chlorate was still the treatment of choice in a May 1944 bulletin (14). The dangers of chemical use were noted by author W. J. Leary, an extension agronomist. He stated "sodium chlorate mixed with organic matter, such as clothing, wood or plant growth . . . becomes a serious fire hazard." One should use caution starting the wood stove after spraying leafy spurge! Mr. Leary also recommended a combination of cultivation and competitive crops for both leafy spurge and creeping jenny (field bindweed) control. This is the first known recommendation of an integrated approach to the control of leafy spurge. The first North Dakota Bimonthly Bulletin was published in September 1938 and included methods to control leafy spurge with sheep (11). This abstract was followed by complete reports in 1939 (12) and 1942 (10). Among the conclusions were that sheep could graze leafy spurge without ill effects and that the weed was controlled while grass production was increased. Over 50 years later similar experiments were conducted, only this time goats (usually Angora) replaced sheep as the grazing animal. The use of sheep to control leafy spurge in North Dakota never became popular. Angora goats were starting to be used for leafy spurge control in the 1990s until the government incentive program for mohair production was curtailed. Because there was no market for the meat in the state and the hair prices were low, it became uneconomical to keep Angora goats just to control leafy spurge.
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