The Return of Native Perennial Bunchgrass Following the Removal of Klamath Weed (Hypericum Perforatum L.) by Imported Beetles

Abstract

During the relatively short period of 4 years since release of imported beetles which feed on it, Klamath weed, HypericUri perforatiun, a serious weed on perhaps a million or more acres of Western range lands, has been brought under strikingly successful control in limited areas by this tool of applied ecology. Though the range in queston has not yet been put under normal grazing, the rapidity and vigor with which the climax hunchgrass, Dantho nia californica, entered the space vacated by the removal of Klamath weed by beetles of the genus Chrysomuiela (= Chrysolina), promises much for the more favorable locations in Humboldt and possibly Menclocino, Trinity and Siskiyou counties in California. The initiation of quantitative studies designed to follow the pattern of vegetational changes and the correlated beetle populations was reported by Iluff aker and Holloway (1949). A brief review of an important survey of these counties by Davy (1902) indicates: 1) The climax grass cover in this area probably consisted of Danithonia californica as the most important component. Other bunchgrasses such as Stipa, Melica, Elymus, Poa, and Festuca were represented, as were important associated forage species such as Trifoliuml spp. (annual and perennial clovers), Lath yrus spp. (wild pea vines), and Wyethia sp. (wild sunflower). 2) There were important early changes, apparently beginning with invasion of the region by such introduced annuals as Erodiumt cicutarpum (filaree) and Avenia fatua (wild oats), later followed, as a result of still heavier stocking, by Hordewun gussoneanum (foxtail), Festuca myuros (rat-tail fescue), and Browrus hlordeaceus (soft chess), and still later by the appearance of weedy arrivals during the last years of the past century. such as Erodium moschatum (musky filaree), Brownus rigidus (broncho grass) Hordeum murinumn (foxtail), Centaurea melitensis (tacaloti), Hypochoeris glabra (hawkbit), and Medicago hispida (burclover). The latter species and the filaree are considered of definite forage value. Some comparison of Davy's survey with the present quantitative results may be worthwhile. For example, Hypochoeris glabra was at that time making its appearance, but now is a definite pest. Also, E. cicutarium, the filaree which thrived prior to his study, is definitely not the species of Erodiurn now most common in either that area or at the 1 Presented in general terms, with slides, at the Western Section Meeting of the Ecological Society at Salt Lake City, June 22, 1950. The general project is under the coordinating supervision of J. K. Holloway and is a cooperative one under the direction of Professor H. S. Smith of the Division of Biological Control, University of California and C. P. Clausen of the Bureau of Entomology and Plant Quarantine of the U. S. Department of Agriculture. The author wishes to express appreciation for the cooperation and assistance given this work by the Division of Agronomy of the University of California, and to acknowledge particularly the help of Professor Ben A. Madson and A. H. Murphy. The detailed program of importation of the beetles, their distribution to the Klamath-weedinfested areas and the general progress of control of the weed, as distinct from this study of the associated vegetational changes in the specific study areas, is reported by Holloway and Huffaker (1951).