Senecio Jacobaea Research Articles

Ecological Relationships between Poisonous Plants and Rangeland Condition: A Review

In the past, excessive numbers of livestock on western U.S. rangelands, reoccurring droughts, and lack of management resulted in retrogression of plant communities. Poisonous plants and other less palatable species increased with declining range condition and livestock were forced to eat these poisonous species because of a shortage of desirable forage, resulting in large, catastrophic losses. The level of management on most western rangelands has improved during the last 60 years, resulting in marked improvement in range condition; yet losses to poisonous plants still occur, though not as large and catastrophic as in the past. Some poisonous species are major components of the pristine, pre-European plant communities [tall larkspur (Delphinium barbeyi Huth), Veratrum californicum Durand, water hemlock (Cicuta douglasii (DC.)Coult. &Rose), bracken fern (Pteridium aquilinum (L.) Kuhn), chokecherry (Prunus virginiana L.), Ponderosa pine (Pinus ponderosa Lawson), and various oak species (Quercus spp.)]. Although populations of many poisonous seral increaser species have declined with better management, they are still components of plant communities and fluctuate with changing precipitation patterns [locoweed (Astragalus and Oxytropis spp.), lupine (Lupinus spp.), death camas (Zigadenus spp.), snakeweed (Gutierrezia spp.), threadleaf groundsel (Senecio longolobis Benth.), low larkspur (Delphinium nuttallianum Pritz.), timber milkvetch (Astragalus miser Dougl. ex Hook.), redstem peavine (A. emoryanus (Rydb.) Cory), western bitterweed (Hymenoxys odorata D.C.), orange sneezeweed (Helenium hoopesii Gray), twin leaf senna (Cassia roemeriana Schelle), and white snakeroot (Eupatorium rugosum Houtt)]. Many of the alien invader species are poisonous: [Halogeton glomeratus (Bieb.) C.A. Mey, St. Johnswort (Hypericum perforatum L.), poison hemlock (Conium maculatum L.), tansy ragwort (Senecio jacobaea L.), hounds tongue (Cynoglossum officinale L.), leafy spurge (Euphorbia esula L.), yellow star thistle (Centaurea solstitialis L.) and other knapweeds (Centaurea spp.)]. Poisoning occurs when livestock consume these plants because they are either relatively more palatable than the associated forage, or from management mistakes of running short of desirable forage. DOI:10.2458/azu_jrm_v55i3_ralphs

Differential effects of insect herbivory on arbuscular mycorrhizal colonization.

A series of field and laboratory experiments were conducted to examine whether natural levels of insect herbivory affect the arbuscular mycorrhizal (AM) colonization of two plant species. The plant species were the highly mycorrhizal (mycotrophic) Plantago lanceolata, which suffers small amounts of insect damage continuously over a growing season and the weakly mycorrhizal (non-mycotrophic) Senecio jacobaea, which is frequently subject to rapid and total defoliation by moth larvae. Herbivory was found to reduce AM colonization in P. lanceolata, but had no effect in S. jacobaea. Similarly, AM colonization reduced the level of leaf damage in P. lanceolata, but had no such effect in S. jacobaea. AM fungi were found to increase growth of P. lanceolata, but this effect was only clearly seen when insects were absent. AM fungi reduced the growth of S. jacobaea irrespective of whether insects were present. It is concluded that the reduction of AM fungal colonization by herbivory in P. lanceolata is due to the reduced amount of photosynthate available to the symbiont. This may only become apparent at threshold levels of insect damage and, below these, increased photosynthesis elicited by the mycorrhiza is able to compensate for foliage loss to the insects. However, in S. jacobaea, the mycorrhiza appears to be an aggressive parasite and insect attack only exacerbates the reduction in biomass. In mycotrophic plants, insect herbivores may be responsible for poor functioning of the symbiosis in field conditions and there is a symmetrical interaction between insects and fungi. However, in non-mycotrophic plants, the interaction is strongly asymmetrical, being entirely in favour of the mycorrhiza.

Ecological relationships between poisonous plants and rangeland condition: A Review

In the past, excessive numbers of livestock on western U.S. rangelands, reoccurring droughts, and lack of management resulted in retrogression of plant communities. Poisonous plants and other less palatable species increased with declining range condition and livestock were forced to eat these poisonous species because of a shortage of desirable forage, resulting in large, catastrophic losses. The level of management on most western rangelands has improved during the last 60 years, resulting in marked improvement in range condition; yet losses to poisonous plants still occur, though not as large and catastrophic as in the past. Some poisonous species are major components of the pristine, pre-European plant communities [tall larkspur (Delphinium barbeyi Huth), Veratrum californicum Durand, water hemlock (Cicuta douglasii (DC.)Coult. Rose), bracken fern (Pteridium aquilinum (L.) Kuhn), chokecherry (Prunus virginiana L.), Ponderosa pine (Pinus ponderosa Lawson), and various oak species (Quercus spp.)]. Although populations of many poisonous seral increaser species have declined with better management, they are still components of plant communities and fluctuate with changing precipitation patterns [locoweed (Astragalus and Oxytropis spp.), lupine (Lupinus spp.), death camas (Zigadenus spp.), snakeweed (Gutierrezia spp.), threadleaf groundsel (Senecio longolobis Benth.), low larkspur (Delphinium nuttallianum Pritz.), timber milkvetch (Astragalus miser Dougl. ex Hook.), redstem peavine (A. emoryanus (Rydb.) Cory), western bitterweed (Hymenoxys odorata D.C.), orange sneezeweed (Helenium hoopesii Gray), twin leaf senna (Cassia roemeriana Schelle), and white snakeroot (Eupatorium rugosum Houtt)]. Many of the alien invader species are poisonous: [Halogeton glomeratus (Bieb.) C.A. Mey, St. Johnswort (Hypericum perforatum L.), poison hemlock (Conium maculatum L.), tansy ragwort (Senecio jacobaea L.), hounds tongue (Cynoglossum officinale L.), leafy spurge (Euphorbia esula L.), yellow star thistle (Centaurea solstitialis L.) and other knapweeds (Centaurea spp.)]. Poisoning occurs when livestock consume these plants because they are either relatively more palatable than the associated forage, or from management mistakes of running short of desirable forage.

Herbicides compromise biological control of ragwort

In spite of ragwort flea beetle (RFB) being present on a Dannevirke dairy farm, pastures were sprayed each winter to reduce ragwort density and limit the risk of ragwort poisoning of stock. The trial on this farm from June 1999 - October 2001, aimed to determine whether herbicide (H) impacted on RFB and how H and RFB each impacted on ragwort growth and persistence. RFBfree areas were created by spraying with insecticide (I). Effects of ragwort on animal health are also reported. High ester 2,4-D (H) boom-sprayed once only, in June 1999, killed most ragwort plants and reduced RFB larvae densities to low levels before the plants died. Once new ragwort established in treatment H, the plants became infested with RFB larvae. RFB larvae were suppressed by I resulting in ragwort density declining more slowly than in treatments where RFB were not suppressed. Insecticide treatments were stopped after 15 months and, at 24 months, ragwort could not be found within the trial area. Ragwort control was attributed to the cessation of herbicide spraying allowing the RFB population to reach a sufficient density to kill both small and large ragwort plants. Sub-clinical ragwort poisoning was found in livers of culled cows that had grazed on ragwort-dense pastures. Keywords: animal health, biological control, Longitarsus jacobaeae, pyrrolizidine alkaloids, ragwort, ragwort flea beetle, Senecio jacobaea

Evidence for two genetically and chemically defined host races of Tyria jacobaeae (Arctiidae, Lepidoptera)

A widely distributed host race of Tyria jacobaeae lives on Senecio jacobaea and related species and accumulates pyrrolizidine alkaloids (“PA race”), another race, which is restricted to the Alps and found on Petasites paradoxus, sequesters sesquiterpenes, such as petasol and isopetasol. Nucleotide sequences of the mitochondrial 16S rDNA gene show 1% sequence divergence, indicating that genetical differences exist between the PA exploiting and the terpene-sequestering host races of T. jacobaeae. This finding suggests that both host races of T. jacobaeae must have been separated for some time already, possibly since the Pleistocene.

Fitness consequences of floral variation in Senecio jacobaea (Asteraceae): evidence from a segregating hybrid population and a resource manipulation experiment

The present study examines some of the ecological factors that might exert selection on floral morphology in Senecio jacobaea, a self-sterile composite which exhibits geographic variation in the frequency of rayed and discoid individuals. Regression analyses of phenotypic data from a large, segregating hybrid population, established in a semi-natural (garden) environment and studied over a 2-year period, revealed a negative relationship between the size of the rays and the average germination rate of the maternal seed crop, a pattern that can be attributed to the reduced germination speed of achenes from ray florets. There was no effect of ray size on the amount of cross-pollination achieved, the proportion of heads infested by larvae of seed flies (Pegohylemyia) and the amount of resources retained for the next flowering season. The lack of resource costs was also apparent in a manipulation experiment with greenhouse-grown plants of the rayed phenotype: artificial removal of all rays at the early bud or flowering stage had no detectable effect on subsequent flower and fruit development, regardless of whether the plants experienced high or low water stress. Given these and other observations, I hypothesize that plant-animal interactions and resource costs sometimes play a minor role in exerting selection on flower morphology and that spatially varying selection on germination behaviour accounts for some of the morph frequency variation in S. jacobaea.

Fitness consequences of floral variation in Senecio Jacobaea (Asteraceae): evidence from a segregating hybrid population and a resource manipulation experiment

The present study examines some of the ecological factors that might exert selection on floral morphology in Senecio jacobaea, a self-sterile composite which exhibits geographic variation in the frequency of rayed and discoid individuals. Regression analyses of phenotypic data from a large, segregating hybrid population, established in a semi-natural (garden) environment and studied over a 2-year period, revealed a negative relationship between the size of the rays and the average germination rate of the maternal seed crop, a pattern that can be attributed to the reduced germination speed of achenes from ray florets. There was no effect of ray size on the amount of cross-pollination achieved, the proportion of heads infested by larvae of seed flies (Pegohylemyia) and the amount of resources retained for the next flowering season. The lack of resource costs was also apparent in a manipulation experiment with greenhouse-grown plants of the rayed phenotype: artificial removal of all rays at the early bud or flowering stage had no detectable effect on subsequent flower and fruit development, regardless of whether the plants experienced high or low water stress. Given these and other observations, I hypothesize that plant–animal interactions and resource costs sometimes play a minor role in exerting selection on flower morphology and that spatially varying selection on germination behaviour accounts for some of the morph frequency variation inS. jacobaea.

The genetic basis of floral variation in Senecio jacobaea (Asteraceae).

The self-incompatible composite Senecio jacobaea (ragwort) exhibits geographic variation in the frequency of rayed and discoid (rayless) individuals. Hybrid progenies from within- and between-morph crosses were established in a seminatural (garden) environment to determine whether patterns of segregation conform to single-gene predictions (as found in other Senecio species), whether the direction of dominance is conducive to rapid evolutionary change in ray morphology, and whether geographically distant populations of the discoid morph utilize the same or different genes to suppress ray development. Data from segregating F2 and BC families were consistent with a genetic model involving one major locus and an unknown number of modifiers. Analysis of F1 progenies from different intermorph crosses using the same rayed plant as a seed parent revealed a variable and incomplete pattern of dominance, with a trend toward partial dominance in some crosses. Hybridizations between discoid populations produced a few rayed progeny (4%), but there was no tendency for the frequency of rayed progeny to increase with the geographic distance separating the parent populations. Results of this study indicate that major mutations have been important for the evolution of discoid populations of ragwort, that ray-suppressing mutations should be directly available to selection in most populations, and that the suppression of rays is conditioned by the same or similar gene(s) in Atlantic and Baltic populations of the discoid taxon.

A Phylogeny of Packera (Senecioneae; Asteraceae) Based on Internal Transcribed Spacer Region Sequence Data and a Broad Sampling of Outgroups

A phylogeny of Packera is presented based on sequence data from the internal transcribed spacer region of nuclear ribosomal DNA of 26 species (28 populations) of Packera and 23 outgroup taxa, including representatives of all three subtribes of the Senecioneae. The results support a Mexican origin for Packera, with its closest relatives found among Old World taxa in the subtribe Senecioninae, such as Senecio jacobaea and Pericallis. Packera species from the west coast of the United States, previously included in the section Bolanderi of Greenman, are part of a basal assemblage including species of Greenman's Mexican section Sanguisorboidei. The rest of Packera separates into two sister groups, one containing species from the Arizona–New Mexico region and the other containing more geographically diverse taxa. Among the outgroups, New World Senecio species are monophyletic and two Tussilaginoid assemblages are strongly supported; the Tephroseroid group (Tephroseris and Sinosenecio) plus Petasites combine with the Luina complex to form a clade of north temperate taxa, and the four Mexican genera (Psacalium, Robinsonecio, Barkleyanthus, and Pittocaulon) form a monophyletic group.

Longevity of buried ragwort seed in four soils

The viability of ragwort (Senecio jacobaea L) seed buried for several years at 0 2 4 6 and 19 21 cm depths was evaluated in four different soil types Seed samples in nylon mesh bags were removed after 1 2 3 5 11 and 16 years burial and their viability determined by germination After 16 years no viable seed was found in the clay soil In the silt loam and peat soils 1 3 viable seed remained while in the sandy soil up to 13 remained viable In the surface 0 2 cm layer of soil it took from 109 to 146 years for the percentage of viable seed to fall to 1 of the original viable seed depending on soil type At the 4 6 and 19 21 cm depths the corresponding times were 128 165 years and 130 180 years

Impact of perennial ryegrass seeding densities on weed emergence growth and development

Research was conducted to determine the effect of perennial ryegrass (Lolium perenne) sowing density on weed growth and development In glasshouse and field experiments perennial ryegrass was sown at rates of 0 5 10 20 40 and 80 kg/ha with 5 kg/ha of white clover (Trifolium repens) With increasing seeding density perennial ryegrass enhanced its competitiveness against all five of the weeds studied viz nodding thistle (Carduus nutans) Californian thistle (Cirsium arvense) Scotch thistle (Cirsium vulgare) ragwort (Senecio jacobaea) and hedge mustard (Sisymbrium officinale) In both trials increases in the perennial ryegrass seeding density did not reduce weed emergence However as perennial ryegrass density increased weed biomass decreased and time to flowering increased

Rearing Conditions for Lambs May Increase Tansy Ragwort Grazing

Grazing by sheep is an accepted method of controlling tansy ragwort (Senecio jacobaea L.), but some flock members seldom eat it. Our objectives were to determine if pre-weaning exposure to tansy ragwort increases later consumption of the plant by lambs, and if confinement with ragwort-eating ewes after weaning facilitates ragwort eating. The sampling periods were Weeks 1, 3, and 12 following weaning. During each period grazing behavior was observed for 1-hour each day and the 24-hour reduction in ragwort volume measured on each of 4 or 5 consecutive days. Lambs exposed to ragwort before weaning removed more ragwort than ragwort-naive lambs during the first 2 sampling periods (P < 0.05). Lambs that grazed with ewes for 11 weeks following weaning ate ragwort more frequently during direct observation, than lambs without ewes during Weeks 3 and 12 (P < 0.05). The ragwort-eating of all lamb groups increased markedly between Weeks 1 and 12 (P < 0.05). This may indicate an increased ability of lambs to consume ragwort with increasing age or an acclimation period during which most lambs come to accept ragwort. Behavioral interventions aimed at increasing the consumption of weeds by lambs may need to take into account age-related differences in toxin tolerances. Exposing lambs to ragwort before weaning and grazing newly-weaned lambs with older ragwort-eating sheep after weaning may increase later ragwort-eating by lambs. DOI:10.2458/azu_jrm_v53i4_sutherland

Rearing conditions for lambs may increase tansy ragwort grazing

Grazing by sheep is an accepted method of controlling tansy ragwort (Senecio jacobaea L.), but some flock members seldom eat it. Our objectives were to determine if pre-weaning exposure to tansy ragwort increases later consumption of the plant by lambs, and if confinement with ragwort-eating ewes after weaning facilitates ragwort eating. The sampling periods were Weeks 1, 3, and 12 following weaning. During each period grazing behavior was observed for 1-hour each day and the 24-hour reduction in ragwort volume measured on each of 4 or 5 consecutive days. Lambs exposed to ragwort before weaning removed more ragwort than ragwort-naive lambs during the first 2 sampling periods (P &lt; 0.05). Lambs that grazed with ewes for 11 weeks following weaning ate ragwort more frequently during direct observation, than lambs without ewes during Weeks 3 and 12 (P &lt; 0.05). The ragwort-eating of all lamb groups increased markedly between Weeks 1 and 12 (P &lt; 0.05). This may indicate an increased ability of lambs to consume ragwort with increasing age or an acclimation period during which most lambs come to accept ragwort. Behavioral interventions aimed at increasing the consumption of weeds by lambs may need to take into account age-related differences in toxin tolerances. Exposing lambs to ragwort before weaning and grazing newly-weaned lambs with older ragwort-eating sheep after weaning may increase later ragwort-eating by lambs.

Biological Control of Plant Invaders: Regional Patterns, Field Experiments, and Structured Population Models

The traditional ways to design biological control systems for plant invaders include (in order of decreasing emphasis) introducing, augmenting, or conserving natural enemies. Manipulating consumer–resource relationships in this way (1) emphasizes top-down control of the invader by consumers rather than bottom-up control of the invader by limiting resources, and (2) contributes to a rising number of control organisms introduced to North America that is creating complexity, redundancy, and risk. New concepts and methods have started to transform the way biological control organisms are found and developed by (1) combining herbivore and resource limitation of plant population growth and (2) using targeted life-cycle disruption, which involves identifying plant life-cycle transitions that are both amenable to manipulation and influential on population growth, and then targeting these for control. To illustrate these developments, we outline an experimental and computational approach for measuring how the processes of disturbance, colonization, and organism interactions (plant competition and herbivory) manifest their influence on weed life cycles and population growth of ragwort Senecio jacobaea, a biennial or short-lived perennial herb. Manipulating these forces may lead to designs of biological control systems that are parsimonious, potent, and pose minimum risk to non-target organisms.

Pyrrolizidine alkaloid distribution in Senecio jacobaea rosettes minimises losses to generalist feeding

AbstractThe within‐plant distribution of pyrrolizidine alkaloids (PAs) was determined in the shoots of vegetative Senecio jacobaea L. Asteraceae plants. Also the distributions of feeding stimulants, soluble sugars and total nitrogen, were determined. PAs were found to decrease with leaf age, sugars were constant, and nitrogen decreased with leaf age. These results were compared with the within‐plant distribution of feeding damage by the generalist herbivores Spodoptera exigua Hübner and Mamestra brassicae L. Both generalists showed a strong preference for older leaves. It was concluded, that the herbivores were forced to feed on sub‐optimal parts of the plant.

Patterns of Herbivore Incidence on Experimental Arrays and Field Populations of Ragwort, Senecio jacobaea

Despite predictions that herbivorous insects should selectively attack high-density host populations, research suggests that different herbivores may exhibit very different responses to host density. I surveyed natural and experimentally planted populations of common ragwort (Senecio jacobaea) for a variety of herbivorous insects. Early and late instar cinnabar moth (Tyria jacobaeae) larvae differed significantly in their incidence patterns on the experimental arrays, with young caterpillars most prevalent on closely spaced hosts, and older caterpillars on more widely spaced plants. The difference suggests opposite density biases may apply to maternal oviposition and larval dispersal behaviours. Two other herbivores (the leaf miner Chromatomyia syngenesiae and the flowerhead boring Botanophila spp.) showed significant biases towards low density hosts in the experimental plantings. In natural populations, another leaf miner, Liriomyza strigata, preferentially attacked low-density plants, whilst C. syngenesiae incidence was highest at intermediate host densities. The difference between natural and experimental populations suggests a difference between colonisation dynamics and longer-term population effects. I review and contrast six possible explanations for the diversity of density responses found amongst herbivores in this and other comparable studies. Most are at least qualitatively consistent with the patterns observed here, and thus require additional research to differentiate.

Rabbit endozoochroy and seedbank build-up in an acidic grassland

The sources of seed for seedbank build-up in an acidic grassland were identified from analysis of differences in seedbank build-up over one year between plots where the input of rabbit pellets to ‘seed-free’ soil had either been left or removed. In parallel, the flux of seed arriving in rabbit pellets was monitored. Pellet seed content and total seed input were highest in late summer/early autumn and again in the spring. The seed content of the pellets was dominated by a small number of species: Sagina apetala, Senecio jacobaea, Urtica dioica and Veronica arvensis. Smaller seeded species were more likely to be present as germinable seed in the pellets. Seedbank build-up as a result of wind, splash or adhesive dispersal totalled 547 seedsm2. The additional effect of allowing seed input in pellets was 267 seedsm2, though this increase was not significant. The total increase in seedbank over one year was equivalent to 15–20% of the seedbank present in undisturbed soil. Eight species showed a significant build-up of seed in the seedbank over one year as a result of all means of dispersal, but only Myosotis discolor showed a significantly higher soil germinable seed content in the plots where pellets had been allowed to remain in situ. The build-up of seed in the seedbank is contrasted with the build-up of vegetation on disturbed areas within the same system.

Sources of plants colonizing experimentally disturbed patches in an acidic grassland, in eastern England

1 The sources of propagules for regeneration in an acidic grassland were identified from analysis of differences in colonization between plots subject to surface (0–5 cm) soil disturbance and plots where surface soil had been replaced by ‘seed‐free’ soil from deeper soil horizons (30–35 cm), and between plots with and without the removal of rabbit pellets. 2 After 1 year, 10 species had a significantly higher cover on plots where the seed bank had been left intact. These included Agrostis capillaris (the dominant species prior to disturbance), Myosotis arvensis and Veronica arvensis. 3 Five species, including Sagina apetala, Senecio jacobaea and Veronica arvensis, showed significantly higher cover on plots where rabbit pellets were left in situ. 4 From calculations it appeared that rabbit‐dispersed seeds accounted for 15% of the developing higher plant cover, other means of dispersal from outside the plot accounted for 40%, and regeneration from the seed bank accounted for 45%. 5 Similar calculations suggested that three higher plant species, Geranium molle, Myosotis arvensis and Senecio jacobaea, appeared to depend most on non‐rabbit dispersed seed for colonization of bare ground. 6 High concentrations of Urtica dioica in pellets contrasted with its poor establishment in the experiment. However, the other common species in the pellets, Sagina apetala, Senecio jacobaea and Veronica arvensis, all established in greater numbers on the plots where the pellets were not removed. 7 Seed bank content correlated well with the pattern of regeneration for Agrostis capillaris, Holcus lanatus, Myosotis arvensis and Veronica arvensis. However, removal of the seed bank did not have a significant effect on the regeneration of either of the most common species in the seed bank, Rumex acetosella and Sagina apetala. 8 No species appeared to be reliant on only one mechanism for regeneration from seed in disturbed areas in this community.

A comparative study on carbohydrate reserves and ethanolic fermentation in the roots of two wetland and non‐wetland species after commencement of hypoxia

The problem of availability of storage carbohydrates (fructans and starch) in oxygen‐deficient roots was investigated in wetland species (Senecio aquaticus Hill., Myosotis palustris[L.] L. Em. Rchb.) and compared with related non‐wetland species (Senecio jacobaea L., Myosotis arvensis[L.] Hill.) with respect to ethanolic fermentation (PDC activity, ethanol production).In response to 24 h of hypoxic treatment, the pyruvate decarboxylase (PDC) activity in roots increased 4‐fold in M. arvensis and S. jacobaea, 2‐fold in S. aquaticus and only slightly in M. palustris. The rise in PDC activity was accompanied by an increase in ethanol content in the roots. The increase in ethanolic fermentation in roots of intact plants was associated with a slight increase in fructose and glucose and in a clear rise in sucrose content during the first 24‐48 h after commencement of the hypoxic treatment. Following 24 h of hypoxia, the content of fructans started to increase significantly for the duration of the experiment (9 days) in the four species. Since starch content changed only slightly during this period, the fructan:starch ratio increased under low energy availability. In the roots of flooding‐tolerant Senecio aquaticus, the ratio shifted most clearly from 2:1 in normoxia to 9:1 in hypoxia. For the roots of the two wetland species investigated, the results indicate a stronger accumulation of carbohydrates accompanied by a lower increase in PDC activity under root hypoxia, when compared with the related non‐wetland species respectively.

Inter‐ and intra‐ species differences in plants as hosts to Tyria jacobaeae

AbstractThe effect of three food plants, Senecio jacobaea L., Senecio vulgaris L. and Tussilago farfara L., and rust infection of two of them on the performance and host choice of Tyria jacobaeae L. was assessed. The nitrogen content of healthy and infected food plants was measured.Larvae reared on S. vulgaris had a lower relative consumption index and higher efficiency of conversion of ingested food than those reared on the other two species. These differences were correlated with the higher nitrogen content of S. vulgaris compared to T. farfara and S. jacobaea. Larvae reared on T. farfara were significantly smaller at pupation than those reared on the other species. In both larval and adult choice tests between healthy plants of the three species, S. jacobaea was always the preferred host plant. Adults completely avoided T. farfara in oviposition choice tests.Infection of S. vulgaris with Coleosporium tussilaginis (Pers) Lev. had no effect on larval performance. Infection of S. vulgaris with Puccinia lagenophorae Cooke. caused differences in larval performance. Infection of T. farfara with C. tussilaginis had a detrimental effect on larval performance: larvae were smaller, fed for longer and had lower growth rates than those reared on healthy T. farfara. Healthy T. farfara had a higher leaf nitrogen content than the infected T. farfara. In choice tests against healthy leaves, larvae avoided leaves of both S. vulgaris and T. farfara infected with C. tussilaginis. Larvae and adults showed no preference between S. vulgaris leaves infected with P. lagenophorae or healthy leaves.In the field, factors such as plant size may be important in dictating adult and larval preference for a particular host plant species. Rust infection of some species influenced larval performance and host choice, demonstrating the importance of studying multitrophic aspects of plant – insect interactions.