Range Weed Control on Rangeland S

158 RANGELANDS 17(5), October 1995 Implementing Effective Noxious Range Weed Control On Rangeland s Joe Antognini, Paul C. Quimby, Jr., Charles E. Turner, and James A. Young Afterdecades of declining interest in The Federal list of noxious weeds list to provide species considered range weed control, public concern has some species that are presently a legally noxious by a western state, has demanded that be something serious pest on United States range- where agriculture is largely range live- done. The nature of the problem has lands such as the grass Curpina vu!- stock production. Each state has a forged coalitions of strange bed fel- garis which occurs in the Pacific slightly to markedly different list of lows. Ranchers face declining forage Northwest. The perennial species of noxious weeds. Some National production, wildlife mangers see Russian thistle, Salsola vermiculata, Forests cross state boundaries and junipers replacing browse species, occurs in California where it provides the conflicting lists can create prob- weed control districts scream that re- valuable forage on rangelands, but is lems. infestation of noxious weeds occurs an alternate host for viral diseases that Historic Weed Control. It is from Range public rangeland watersheds, spread to crops. There are serious worth while to look at the of and nature history conservancy groups decry range weeds that are not yet intro- range weed control to obtain a per- loss of biological diversity to alien duced to the United States that are spective on how the of weeds. This principles has culminated in pro- missing from the list. For example, range weed control evolved. The national posed legislation directing Slipa campensis is an annual needle- development of phenoxy herbicides public land management agencies to grass found in southwesternAsia that after World War II had control noxious great applica- weeds on federal is too tough and awned to serve as tion in vegetation managementon lands and to provide adequate funding forage for camels. It probably is adapt- rangelands. Most of the applications for such an effort. ed to southern Great Basin ranges. involved control of woody species that Our purpose is to provide a brief his- From the species that are included had increased on lands. A torical grazing perspectiveon range weed con- and are absent, range managers have major example was the use of 2,4-D to trol in the context of present weed apparently not had a major role in control excessively dense stands of inventory, biological and herbicidal developing the Federal noxious weed sagebrush (Artemisia to control and tridentafa) technologies, regulatory list. release perennial grasses from com- policies. We use the Nevada noxious weed petition. Big sagebrush is neither a Noxious Weeds. The proposed federal is legislation specifically aimed Table 1. Adapted from the Federal list of noxious weeds as maintained by USDA-Animal toward those and Plant Health weeds that have been Inspection Service. The list has the major categories: 1) aquatic, 2) legally designated by state and/or the terrestrial, and 3) parasitic species. The portion of the terrestrial category that would federal government as noxious appearmost likelyto influence rangelandenvironments is reported in the table. (Tables 1 and 2). These weeds have characteristics that make them a Scientific name Common name threat to agronomic agriculture, graz- Avena sterilis sterile oat ing lands, and the environment in gen- Crupina vulgaris common crupina eral if are Digitaria abyssinica African couchgrass they allowed to be intro- 0. velutina duced or annual couchgrass spread without control. The Euphorbia prunifolia connotation of painted euphorbia legal being a noxious Galega officinalis goatsrue weed bans importation, transportation, Imperata brasiliensis Brazilian satintail and contaminationin commercial seed lschaemum rugosum murainograss chinensis lots by these species. Leptochloa Asian sprangletop Opuntia aurantiaca jointed prickly pear Pennisetum clandestinum Kikuyugrass P. macrourum African feathergrass Authors are P. retired national program leader for polystachion missiongrass weed science, research leader for biological con- Prosopis (There are 25 on the trol of species list) weeds, botanist and range scientist, Salsola vermiculata wormleaf salsola USDA, Agric. Res. Serv. Urochloa panicoides liverseed grass RANGELANDS 17(5), October 1995 159 Table 2. Weeds that are legally classified as noxious in the state of Nevada. Each state Principles of range weed control that has a list ofweeds considered noxious. The more wide spread and troublesome weeds grew out of the halogeton control pro- may occur on most of the state lists. A weed declared noxious in a particular state may were: have to have an state. The state lists are gram 1) you or may not have the same legaldesignation in a neighboring to the weed in addition to the Federal noxious weed list. adapted species replace once it is controlled, and 2) you have to understand the seed ecology of the Scientific name Common name weed being controlled. At the time it Austrian fieldcress Rorippa austriaca was not recognized the brown form of Sphaerophysa salsula Austrian peaweed had camelorum Camelthorn halogeton seeds delayed germi- Alhagi for Hypericurn perforatum Kiamath weed nation and persisted in seedbanks Coniurn macu/a turn Poison hemlock many years. In the more mesic big Cicuta spp. Hemlock sagebrush zone several million acres nettle Solanum carolinense Carolina horse were seeded to crested wheatgrass S. elaeagnifoliurn White horse nettle to Centaurea diffusa Diffuse knapweed (Agropyron desertorum) biologically In the salt desert C. repens Russian knapweed suppress halogeton. C. iberica Iberian star thistle zone an adapted perennial species to C. calcitrapa Purple star thistle replace halogeton was not available. C. so/sti/tialis Yellow star thistle The native shrubs around halogeton Euphorbia esula Leafyspurge Licorice infestations were susceptible to appli- G/ycyrrhiza lepidota The unintentional Sa/via aethiopis Mediterranean sage cations of 2,4-D. Taeniatherurn caput-meduase subsp. asperum Medusahead killing of native shrubs enlarged the Tribuli is terrestris Puncture vine area where halogeton was adapted Cirsiurn arvense Canada thistle and the brown seeds provided Carduus nutans Musk thistle to occupy the sites. Onopordum acanthium Scotch thistle seedlings Sonchus arvensis Sowthistle A second generation of herbicides Linara dalmatica Dalmatian toadflax represented by such compounds as Cardaria draba Hoary cress atrazine were developed for use in Lepidiurn Iatifo/iurn Perennial pepperweed herbicidal fallow techniques for the Perennial Sorghum spp. species - control of such herbaceous range weeds as cheatgrass (Bromus tecto- noxious nor a self invasive species excellent seed producer and is a phe- rum), to permit the establishment of outside of areas where it is adapted, notypically and genotypicalhighly vari- perennial herbaceous or woody of but it is a long-lived, woody perennial able. It required careful timing and species. Cheatgrass is an example that can increase in population density repeated applications of 2,4-D to sup- a highly invasive species that is not a and suppresses perennial herbaceous press weeds like Canada thistle, with noxious weed. species. Range managers soon eradication being seldom achieved. Biological Control. The use of learned there was no use in controlling Attempted control of the introduced introduced organisms that suppress unless there were suffi- poisonous plant halogeton (Halogeton populationsof a specific weed has had big sagebrush The cient perennial grasses in the under glomeratus) with applications of 2,4-0 notable success on rangelands. story to preempt the environmental did much to further elucidate the basic control of Klamath weed (Hypericum potential released by reducing the principals of range weed control. perforatum), a poisonous perennial brush. You had to be able to step from Halogeton is a fleshy annual that when herb, is an example of biological con- remnant perennial grass bunch to young is susceptible to applications of trol with an introduced insect. Another, bunch for the brush control to be effec- 2,4-D. Halogeton produces huge more recent example is the control of a tive in increasing desirable forage pro- amounts of black seeds, but they have tansey ragwort (Seneclo jacobaea), duction. very short lives in seedbanks. Initially poisonous biennial, using insects intro- control The first generation herbicides such it appeared that control of one or two duced from Europe. Biological as 2,4-0 were used for attempted con- generations of a given infestation does not lead to eradication, but rather of trol of such noxious range weeds as would result in eradication. Halogeton long term, sustainable suppression Canada thistle (Cirsium arvense). is not a particularly competitive weed populations. Research on the Canada thistle shares many of the species and is readily suppressed by biological control of range weeds is characteristicsof perennial noxious establishment of perennial plants. The underway for several other species well as weeds in having creeping rootstocks rapid spread of halogeton across the using plant pathogens as that give rise to multiple stems, pro- Intermountain Area during the 1940s insects (Table 3). dense colonies that virtually was a symptom of the underlying The failure to find a biological control ducing illustrates smother through competition, all other degradationof many

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