ENTOMOPHAGA 35 (I), 1990, 71-77

BIOLOGICAL CONTROL OF JACOBAEA IN NORTHERN CALIFORNIA, AN ENDURING SUCCESS

R. W. PEMBERTON (t) & C. E. TURNER

Rangeland Insect Lab, USDA-ARS, Montana State University, Bozeman, Montana 59717 Biological Control of Weeds Western Regional Research Center USDA-ARS, Albany, California 94710

Seneciojacobaea, a poisonous weed from Eurasia, was brought under successful biological control in the Ft. Bragg, California area by 1976, through the combined action of the defoliating cinnabar moth (Tyriajacobaeae) and a root feeding flea beetle (Longitarsusjacobaeae). In 1987, 4 previously infested Ft. Bragg sites (3 sites where control had been documented and another unstudied site) were examined. Senecio jacobaea densities at these sites were 0.0, 0.0, 0.01 and 0.18 /m 2, indicating both continued and improved control of the weed. The flea beetle and the cinnabar moth both persist at the sites, despite very low numbers of S.jacobaea plants. The control of S. jacobaea has resulted in the return of near natural vegetation at the 2 coastal prairie sites and regained productivity at the 2 pasture sites.

KEY-WORDS : Biological control, cinnabar moth, Longitarsusjacobaeae, poiso- nous , Seneciojacobaea, tansy ragwort, Tyria jacobaeae.

INTRODUCTION

THE WEED PROBLEM Tansy ragwort, (Senecio jacobaea L. : ) is a biennial or short lived perennial herb that is native to Europe eastward to Siberia (Harper & Wood, 1957). The plant is an introduced weed in New Zealand, Australia, South Africa, Argentina, Brazil, Canada, and the United States (Holm et al., 1979). Tansy ragwort contains toxic pyrrolizidine alkaloids which cause liver damage and death to cattle and horses that ingest it (Kingsbury, 1964 ; Harris et aL, 1984). The weed can also displace more desirable forage plants and dominate pastures and other disturbed land it infests. In North America, S.jacobaea has been a problem in northeastern Canada and along the Pacific Coast in British Columbia, Washington, Oregon and Northern California (Frick & Holloway, 1964). Some tansy ragwort infestations in British Columbia appear to date from

(1) Present address: Asian Parasite Laboratory, USDA Agriculture Research Service, Seoul, Korea c/o American Embassy APO San Francisco 96301 72 R. W. PEMBERTON& C. E. TURNER

1913 (Harris et al., 1971). The first Oregon record for the plant was at Portland in 1922 (Isaacson, 1978). Alice Eastwood made the I st California collection of tansy ragwort at Fort Bragg, Mendicino Co. in August 1912 (Alice Eastwood No. 1648 California Academy of Sciences, D. Bathe, pers. comm.). By the mid 1950s tansy ragwort had become an important weed of the Pacific Coast (Gilkey, 1957 ; Harris et al., 1971). Chemical and mechanical control of tansy ragwort have usually proven to be unecono- mical since most of the lands that the weed infests have relatively low productivity (Isaacson, 1973). Losses in Oregon were estimated to be at least $1.5 million and possibly as high as 10 million per year (Isaacson, 1978).

BIOLOGICAL CONTROL HISTORY In the late 1950s a biological control program was begun against tansy ragwort by the USDA's Agriculture Research Service in Albany, Calif. (Holloway & Huffaker, 1960). Many European insect enemies of tansy ragwort were already known (Cameron, 1935 ; Harper & Wood, 1957), including the cinnabar moth (Tyriajacobaeae L., Arctidae) and a seedhead fly (Pegohylemyia seneciella Meade, Anthomyidae) which had already been (or were being) introduced to Australia and New Zealand (Julien, 1987). The I st insect to be released into North America for biological control of ragwort was the cinnabar moth, whose larvae feed on the foliage and flowers of tansy ragwort during the summer. In 1959 and 1961, 4,800 larvae, originating from French collections, were released at two Ft. Bragg, California sites (Frick & Holloway, 1964). These established in 1960 and 1962 (Frick & Holloway, 1964), and by 1963 the moth was abundant enough to defoliate almost I00 % of the ragwort at some sites (Hawkes & Johnson, 1978). This defoliation reduced the number of flowering stems but increased the number of rosette plants (Hawkes & Johnson, 1978). Since more control was needed, the seedhead fly (P. seneciella), whose larvae feed on the developing ragwort seeds, was released at Ft. Bragg in 1966. The fly, which was from France, established, but then was lost when the release site was destroyed (L. Andres, pers. comm.). A 3 rd insect Longitarsusjacobaeae (Waterhouse) (Chrysomelidae), was released in the Ft. Bragg area in 1968, 1969, and 1970 (Frick & Johnson, 1973). This flea beetle, which was collected from Italy, feeds on the root crowns, stems and leaf petioles of the plants during the larval stage in the late autumn, winter and spring (Hawkes & Johnson, 1978). By 1970, L. jacobaeae had established, and by 1972 the 955 beetles originally released had generated very large populations. At the Foresti ranch, where 511 beetles had been released, the weed was almost completely eliminated over an estimated 5 hectares by 1973, and the beetles could be found as far as 2 km from the site (Hawkes & Johnson, 1978). Measurements of tansy ragwort decline at 3 Fort Bragg sites continued until 1975 and 1976 when the densities had been reduced to 0.0, 0.6 and 0.2 plants/m 2 (Hawkes & Johnson, 1978).

STUDY OBJECTIVES We undertook the study to learn : l) if tansy ragwort at Ft. Bragg was still being controlled by released agents, and if so, to what degree, 2) if the cinnabar moth and the ragwort flea beetle persisted in the area even at low plant densities, and 3) if control had been maintained, what vegetation had replaced tansy ragwort.

MATERIALS AND METHODS Four Ft. Bragg sites were examined on September 8 and 9, 1987. Three of these sites (Todd Point, Foresti ranch and Smith ranch) were flea beetle release sites, where the BIOLOGICAL CONTROL OF SENECIO JACOBAEA 73 cinnabar moth had also been released or had colonized by the mid 1960s. The ragwort at the sites had been reduced to very low levels by the combined action of the flea beetle and moth (Hawkes & Johnson, 1978). The 4 th site, at MacKerricher State Park, had a small, very dense ragwort infestation in 1976, when both the flea beetle and the cinnabar moth had spread to the site (J. Drueeker & R. Hawkes, pers. comm.). Tansy ragwort density was measured by taking 200 one m 2 samples, at 5 meter intervals, along transects that zigzagged across the long and wide axes of the sites. The number of flowering and rosette form plants were recorded in each sample. When no ragwort was found in the samples, the site was thoroughly searched for plants. The number of ragwort plants at each site with flea beetles and cinnabar moths or their feeding damage were counted when plant densities were very low, or sampled (every 5 th plant was examined until 25 plants were checked) when plant densities were high. The Todd Point ragworts were not checked for insects. Qualitative listings of the dominant plants and their main plant associates were made at each site to get an idea of the replacement vegetation where ragwort had been controlled.

RESULTS AND DISCUSSION

Table 1 shows the densities of tansy ragwort we measured, and for comparison the ragwort densities measured from 1966 to 1976 by Hawkes & Johnson (1978). The Foresti ranch site is a pasture of moist prairie on river bottomland bordered by a Salix sp., located on the western and northern banks of Ten Mile River. The pasture has been lightly grazed (K. Olson, ranch owner, pers. comm.). No ragwort plants were found

TABLE 1 Tansy ragwort plants/m 2 at 4 Ft. Bragg. California sites

Autumn Foresti Todd Smith MacKerricher Sample Ranch Point Ranch State Park Dates 1966 -- 53.3 (l) _ _ (Tyria present) 1968 ( Tyria present ( Tyria -- Longitarsus present) released) 1969 15.3 1972 -- 71.1 (Longitarsus -- ( Longi tarsus released) released) 1973 -- 39.5 11.7 (i) __ 1974 -- 6.9 7.4 very dense (2). ( Longitarsus presen0 1975 0.0 0.6 0.5 -- 1976 (Spring) -- 0.6 0.2 (Tyria presenO (3) 1987 0.0 0.0 0.18 0.01

(t) pre 1987 densities from Hawkes 1978. (2) John Druecker pers. comm. 1988. (3) Robert Hawkes pers. comm. 1988. 74 R. W. PEMBERTON& C. E. TURNER

in the 200 samples. Hawkes & Johnson (1978) also found no ragwort plants in 100 square meter samples. Twenty-one flowering ragwort plants but no rosettes were found within the ca. 4 hectare sample area. Adult L. jacobaeae >. 10/plant) were observed on 17 of these plants. Cinnabar moth feeding damage to the flowers was noted on one plant. The dominant plants were a Scirpus sp. and Holcus lanatus L. The primary associates were: Baccharis pilularis DeCandolle, Cirsium arvense (L.) Scopoli, C. vulgate (Savi) Tenore, Conium maculatum L., Digitalis purpurea L., Monardella villosa Bentham, Potentilla sp., Rubus sp., Rumex crispus L. and R. pulcher L, Tansy ragwort has been replaced by a mixture of native forbs, the introduced forage grass H. lanatus and exotic weeds. The pasture has regained its utility, although introduced thistles reduce its productivity. The Todd Point site is a coastal prairie on a bluff overlooking the ocean. The field was used to pasture sheep but no grazing has taken place since the early 1950s (J. Druecker, pets. comm.). No ragwort plants were found in the 200 samples and only 6 flowering plants were discovered in a search of the ca. 30 hectare field. Hawkes & Johnson (1978) recorded 0.6 plants/m 2 in 100 samples examined in 1976. There has been a significant improvement in the control, although the greatest reduction occurred from 1966 to 1974 when the ragwort population dropped from 53.3 to 6.9 plants/m 2. The dominant plants at the site were H. lanatus, Pteridium aquilinum (L.) Kuhn, and a Rubus sp. The most evident associated plants were: Achillea millefolium L., Anaphalis margaritacea (L.) Bentham ex Clarke, B. pilularis, Cirsium quercetorum (Gray) Jepson, Eschscholzia californica Chamisso, Fragaria chiloensis (L.) Duchesne, Heracleum lanatum Michaux, Hypochoeris radicata L., Iris douglasiana Herbert, Lupinus sp., Plantago lanceolata L., Raphanus sativus L. and Stachys rigida Nutall and Bentham. The vegetation was usually below one meter high but dense enough to often make walking difficult. What had been a << sea of yellow ragwort >> (J. Druecker, pers. comm.) has returned to a relatively natural state consisting of mostly native vegetation. The Smith ranch site is a ca. one hectare pasture on the east side of Ten Mile River. The field is bounded by : Acer macrophyllum Pursh, Sequoia sempervirens (D. Don) Endl., Alnus sp., and a Salix sp. The pasture was heavily grazed, as it had been in the 1970s (R. Hawkes, pers. comm.). Nine flowering and 26 rosette stage tansy ragwort plants were found in 14 of 200 samples yielding a density of 0.18 plants/m 2. The ragwort population density in 1976 was 0.20 plants/m 2 (Hawkes & Johnson, 1978), a very similar level. Adult L. jacobaeae beetles were found on 8 of the 25 plants examined, with fewer than 10 beetles on each of these 8 plants. The dominant plants were: Carduus pycnocephalus L., Scirpus sp., and remnants of unknown grasses. The common associates were Convolvulus arvensis L., Cyperus sp., Hypochoeris radicata, Rumex acetosella L., Taraxacum officinale G. H. Weber, and tansy ragwort. Although the ragwort cover is very low compared to the 11.7 plants/m 2 recorded in 1973, the plant is a prominent part of the herbaceous vegetation left after grazing. Mature ragwort plants are avoided by cattle and the plants do well on <~ run down >> pastures (Harris et al., 1971), probably because of reduced competition from other plants. The MacKerricher State Park site is a coastal prairie with a few scattered, small Pinus contorta D. Don and P. muricata Douglas ex London. The prairie has not been grazed since the formation of the park in the early 1950s. There were no historical measurements of the ragwort infestation at this site. The main very dense ragwort ~< patch >> is estimated to have occupied 0.15 hectares in 1974, when the ragwort flea beetles were first found there (J. Druecker, pers. comm.). BIOLOGICALCONTROL OF SENECIO JACOBAEA 75

Two flowering plants were found in 2 of the 200 samples giving a ragwort density of 0.01 plants/m 2. A total of 14 flowering and 3 rosettes were found in the ca. 3 hectare sample area. Eight of the 14 flowering plants had one or more adult L. jacobaeae. One plant had a late instar T. jacobaeae larva and another appeared to be defoliated by the caterpillars. The dominant plants were H. lanatus and a Carex sp. The main associates were Plantago lanceolata L., F. chiloensis, Potentilla sp., Rubus sp., and sp. The ragwort at the MacKerricher site has been controlled and replaced by mostly native vegetation. Tansy ragwort at Ft. Bragg remains under excellent biological control. Since 1976, there has been a slight improvement in the degree of control at 2 of the 3 previously studied sites. Both T. jacobaeae and L. jacobaeae have persisted on the sites even at very low numbers of ragwort plants. Adult flea beetles were observed on 32, 57 and 81% of the plants at the Smith, MacKerricher and Foresti sites. The cinnabar moth, which is more active earlier in the season, was present but less evident on MacKerricher and Foresti ragwort plants. The control of ragwort has resulted in a significant improvement in the vegetation at all 4 sites. The coastal prairie sites have returned to relatively natural states. The pasture sites have regained their productivity but have more introduced weeds than the prairie sites. This difference is probably due to grazing, particularly at the Smith ranch site which is overgrazed. The Smith ranch site had the least competing vegetation and the most ragwort of the 4 sites. This very successful biological control project against tansy ragwort appears to be due to the excellent complementary actions of the cinnabar moth and the ragwort flea beetle (Hawkes & Johnson, 1978 ; MeEvoy, 1985). The moth's summer feeding on the leaves and flowers and the beetle's feeding on leaves, in leaf petioles, crowns and roots subject most of the plant to attack and maintains herbivore pressure throughout most of the year. The natural enemies and tansy ragwort appear to have reached an equilibrium in which each regulates the other's populations to low numbers and densities. Significant biological control of tansy ragwort by L. jacobaea and T. jacobaeae has also been achieved in Redwood National Park, Del Notre Co., Calif. (Mastrogiuseppe et al., 1983) ; Oregon (Hawkes, 1981 ; MeEvoy, 1985) ; Washington (Piper, 1985) ; and to a lesser degree Canada (Julien, 1987).

ACKNOWLEDGEMENTS

We wish to recognize the people who p~/rticipated in the very successful biological control program against tansy ragwort : present or former USDA-ARS researchers, L. A. Andres, K. E. Frick, R. B. Hawkes, J.K. Holloway, G.R. Johnson, A. Mayfield, H.L. Parker, and A. Rizza ; and former Mendicino Co. Calif. biologists J. Dmeeker and F. Cogbnrn. We thank J. Dmeeker, Ft. Bragg, Calif., for helping us find and have access to original study sites and for his valuable historical knowledge. D. Barbe, CDFA, Sacramento, Calif., kindly provided information on the first record of S.jacobaea in Calif. We are grateful to L. A. Andres, USDA, ARS, Albany, Calif., and R. B. Hawkes, Oregon State Dept. Agric., Salem, Oregon, for discussions about the program and for critical reviews of the manuscript. We thank P. Wick, Montana State University, Bozeman, MT for preparation of the French summary.

RI~SUMI~

Contr61e biologique de Senecio jacobaea en Californie du Nord : un succ~s persistant

Seneciojacobaea, mauvaise herbe originaire d'Eurasie, a pu &re contrrl~e biologiquement de faqon efficace dans la rrgion de Fort Bragg en Californie, fi partir de 1976, grace fi l'action combinre d'un 76 R. W. PEMBERTON & C. E. TURNER papillon nocturne se nourrissant des feuilles et des fleurs (Tyriajacobaeae) ct d'un col6optdre se nourrissant des racines (Longitarsusjacobaeae). En 1987, les 4 sites de la r6gion de Fort Bragg pr6chdemment infest6s (3 sites avcc suivi et un quatri6me non suivi), ont 6t6 visit6sde nouveau. Lcs dcnsit6s de Seneciojacobaea sur ces 4 sites 6taient respectivemcnt de 0,0, 0,0, 0,01, ct 0,18 plants/m 2, cc qui t6moignait fi la lois du maintien et de ram61ioration de raction de contr61e. Le col6opt6re et le papillon 6taient toujours pr6sents sur les diff6rents sites malgr6 le nombre tr6s faible dc plants/m 2 de Seneeiojacobeae. Le contr61c de Seneciojacobeae a pennis le r6tabfissement presque int6gral de la v6g6tation naturelle initialcsur les 2 sites class6s comme << Prairie Coti6re, et un regain significatif de la productivit6 sur les 2 autres sites formant chacun un pfituragc.

MOTS CLIPS : Contr61e biologique, Longitarsus jacobaeae, Senecio jacobaea, Tyria jacobaeae. Received : 5 September 1988 ; Accepted : 19 December 1988.

REFERENCES

Cameron, E. -- 1935. A study of the natural control of ragwort [Seneciojacobaea L.] ~ J. Ecol., 23, 265-332. Frick, K. E. & Holloway, J. K. -- 1964. Establishment of the cinnabar moth, Tyria jacobaeae, on tansy ragwort in the western United States. -- J. Econ. Entomol., 57, 152-154. Frick, K. E. & Johnson, G. R. -- 1973. Longitarsus jacobaeae [Coleoptera : Chrysomelidae], a flea beetle for the biological control of tansy ragwort. 4. Life history and adult aestivation of an Italian biotype. -- Ann. Entomol. Soc. Am., 66, 358-367. Gilkey, H, M. -- 1957. Weeds of the Pacific Northwest -- Oregon State College, Corvallis, 382-383. Harper, J. L. & Wood, W. A. ~ 1957. Seneciojacobaea L., Biological flora of the British Isles. -- J. Ecol., 45, 617-639. Harris, P., Wilkinson, A. T. S., Neary, M. E., & Thompson, L. S. -- 1971. Seneciojacobaea L., tansy ragwort [Compositae]. In : Biological Control programmes against insects and weeds in Canada. -- Commonw. Agric. Bureaux, Farnham Royal, Slough, 97-104. Harris, P., Wilkinson, A. T. S. & Myers, J.H. -- 1984. Senecio jacobaea L. [Compositae]. In: Biological control programmes against insects and weeds in Canada 1969-1980 (J, S. Kelleher & M. A. Huime, eds.). -- Commonw. Agric. Bureaux, Franham Royal, Slough, 195-201. Hawkes, R. B. & Johnson, G. R. -- 1978. Longitarsusjacobaeae aids moth in the biological control of tansy ragwort. In: Proc. IV Int. Syrup. Biol. Contr. Weeds (T. E. Freeman, ed.). -- Univ. Florida, Gainesville, 193-196. Hawkes, R. B. q 1981. Biological Control of tansy ragwort in the state of Oregon. In : Proc. V Int. Symp. Biol. Contr. Weeds (E.S. DelFosse, ed.). -- Commonw. Sci. Ind. Res. Organ., Australia, 623-626. Holloway, J. K. & Huffaker, C. B. -- 1960. Insects on our side. -- Agric. Res., 8, 12. Holm, L., Pancho, J. P., Hcrberger, J. B. & Plucknett, D. L. -- 1979. A geographical atlas of world weeds.- Wiley & Sons, New York. Isaacson, D.L.- 1973. A life table for the cinnabar moth, Tyria jacobaeae, in Oregon. -- Entomophaga, 18, 291-303. Isaacson, D. L. -- 1978. The role of biological agents in integrated control of tansy ragwort. In : Proc. IV Int: Symp. Biol. Contr. Weeds. (T. E. Freeman, ed.). -- Univ. Florida, Gainesville, 189-192. Julien, M. H. (ed.). -- 1987. Biological control of weeds, a world catalogue of agents and their target weeds, 2 na ed. -- Commonw. Agric. Bureaux Int., WaUingford, Oxon, U.K., 19-21. Kingslmry, J.M. -- 1964. Poisonous plants of the United States and Canada. -- Prentice Hall, Englewood Ciffs, New Jersey, 425-435. BIOLOGICAL CONTROL OF SENECIO JACOBAEA 77

Mastrogiuseppe, R. J., Blair, N. T. & Vezie, D. J. -- 1983. Artificial and biological control of tansy ragwort, Senecio jacobaea L., in Redwood National Park, California -- Proc. 1~t Biennal Conf. Res. Calif. National Parks, Davis, Calif., 83-89. McEvoy, P. B. -- 1985. Depression in ragwort [Seneciojacobaea] abundance following introduction of Tyria jacobaeae and Longitarsus jacobaeae on the central coast of Oregon. In : Proc. VI Int. Syrup. Biol. Contr. Weeds. 0g. S. Delfosse, ed.). -- Agric. Canada, Ottawa, 57-64. Piper, G. L. -- 1985. Biological Control of weeds in Washington : status report. In : Proc. VI Int. Syrup. Biol. Contr. Weeds. 0g. S. Delfosse, ed.). --Agric. Canada, Ottawa, 817-826.