Characterization and evaluation of Ramularia crupinae,a candidate for biological control,and of its host,two varieties of Crupina vulgaris in the United States

Crupina vulgaris (common crupina) is an invasive annual plant of rangelands and pastures in the United States (USA). There are two varieties of C. vulgaris in the USA that differ morphologically and biologically, particularly in requirements for bolting. A vernalization protocol enabled synchronization of bolting, thus facilitating concurrent comparative studies of both varieties. Leaf-removal experiments suggest that all leaves provide photosynthate for seed fill, but the cauline leaves, on a relative basis, produced 1.7–4 times more seed per g than rosette leaves, suggesting disease on the cauline leaves has greater potential to reduce seed production than disease on rosette leaves. Ramularia crupinae, a leaf-spotting fungus, was evaluated for biological control. A single inoculation caused a 47% reduction in root dry weight, and seed yield was reduced by 39% as the number of inoculations increased from 0 (controls) to 3. None of 35 non-target taxa, i.e., species, cultivars, and varieties, in the tribe Cardueae was damaged from inoculation by R. crupinae, including safflower, which developed a few, small necrotic spots on old leaves. Best Linear Unbiased Predictors (BLUPs), generated by a mixed model analysis of disease reaction and genetic relatedness data, indicated that only C. vulgaris varieties were susceptible to disease; i.e., BLUPs were significantly different from zero (p > |t| < 0.05). None of the other taxa had BLUP estimators that were significantly different from zero and were, therefore, determined to be not susceptible to disease by R. crupinae. Results suggest that R. crupinae is a potentially good candidate for biological control of this important weed pest and would likely not affect other species of importance in the USA.     

The anthers of Senecio vulgaris (Asteraceae): saltatory evolution caught in the act

Anthers of the common annual weed, Senecio vulgaris, show an incomplete development of the two adaxial pollen sacs (microsporangia, MS). One or both adaxial MS can be missing, or they are replaced by sterile lobes. The reduction is stronger in the derived subspecies, S. vulgaris var. vulgaris than in the ancestral subspecies, S. vulgaris ssp. denticulatus. This character in S. vulgaris differs from the usual complete reduction of adaxial MS in other, independent instances of disporangiate anthers in the Asteraceae. It corresponds to the transition phenotypes associated with various recombinant genotypes derived from artificial crosses between tetrasporangiate (4 MS) and disporangiate (2 MS) species in the Asteracean genus Microseris. Senecio vulgaris could be a rare natural instance of homozygosity for a major gene permitting reduction of the adaxial MS in which the expression of the reduced phenotype is determined by different numbers of modifiers in the two subspecies.     

Morphological and molecular characterisation of Puccinia lagenophorae, now present in central North America

In June 2004, a rust fungus not previously reported for Oklahoma was found occurring naturally on the weed, common groundsel, Senecio vulgaris, in pots in a commercial container nursery in northeastern Oklahoma. Host symptoms and morphology of teliospores and aeciospores of the fungus were consistent with those of Puccinia lagenophorae, a recent introduction into North America that has, as yet, been reported only on the East and West Coasts of the USA. This is the first report of the rust in central regions of North America. The rust is believed to be native to Australia and New Zealand and subsequently reported in most continents on numerous species and genera of the Asteraceae. Some authors in Europe consider the rust on Bellis as different from the one on Senecio, naming it Puccinia distincta. Our ITS1‐5.8S‐ITS2 ribosomal DNA sequence data, however, show homology with P. distincta sequences from Europe, indicating there is only one morphologically‐variable polyphagous species. Presumably, the rust was introduced into Oklahoma on infected plants from the West Coast of the USA, the source of most plant material in the commercial nursery where it was found. The rust is potentially important on several ornamental Asteraceae in North America as it has become in Europe, where it spreads rapidly throughout that continent following its introduction there in the early 1960s.     

The system management approach of biological weed control: Some theoretical considerations and aspects of application

Theoretical considerations behind the system management approach of biological weed control are presented. These include, a part describing and explaining the effects of parasitic fungi on crop – weed competition, a part describing and explaining the epidemic spread of parasitic fungi on weeds, and a part relating crop – weed competition at the population level to epidemics. The theoretical framework developed may also provide a basis for the use of other natural enemies, like insects, for biological weed control following the system management approach. Aspects of application are discussed using data of the interaction between the annual weed Senecio vulgaris and the rust fungusPuccinia lagenophorae.     

Systematics of <Emphasis Type="Italic">Mycosphaerella</Emphasis> species associated with the invasive weed <Emphasis Type="Italic">Fallopia japonica</Emphasis>, including the potential biological control agent <Emphasis Type="Italic">M. polygoni-cuspidati</Emphasis>

Native to Japan, Fallopia japonica, most frequently referred to as Japanese knotweed, is a highly problematic invasive weed, particularly in the UK and North America. During surveys for natural enemies of this plant in Japan, two species of Mycosphaerella were collected. One of these was identified as M. polygoni-cuspidati, and is redescribed and neotypified. Causing a damaging leaf spot disease of F. japonica throughout its natural range in Japan, it is absent from the host’s exotic range. The restriction of M. polygoni-cuspidati to F. japonica in its center of origin, together with its severe impact on host fitness, indicates that this is a coevolved natural enemy with high potential as a classical biological control agent for the long-term management of this ecologically and economically important weed. In the field, the fungus has a reduced life cycle, with only spermogonia and pseudothecia (ascomata) being formed. Ascospores are the primary source of infection, and studies show that the mycelium from in vitro cultures is also infective and hyphae penetrate mainly via the stomata. A further, undescribed species of Mycosphaerella co-occurs with M. polygoni-cuspidati, here proposed as the new species M. shimabarensis. Both species have been studied using cultural, morphological and molecular phylogenetic methods.     

入侵害草薇甘菊的防除研究进展

对薇甘菊MikaniamicranthaH.B.K.防除的最新研究进展进行了综述。薇甘菊的防除,目前主要采用人工清除、化学防除、生态防除和生物防治等方法,其中生物防治是最有效的防治方法之一。生物防治中艳婀珍蝶Actinotethaliapyrrha和安婀珍蝶A.anteas是较有前途的两种昆虫;柄锈菌PucciniaspegazzinideToni能使薇甘菊生长受阻、矮化、枯萎和死亡,在中国有利用的可能;凤凰木Delonixregia、血桐Macarangatanarius、榥伞枫Heteropanaxfragrans可以利用植物相克作用控制薇甘菊;菟丝子属Cuscuta的3种菟丝子能侵染薇甘菊,其中田野菟丝子Cuscutacampestris对薇甘菊控制作用较强,是以草治草的一种新方法。     

Unrelated facultative endosymbionts protect aphids against a fungal pathogen

The importance of microbial facultative endosymbionts to insects is increasingly being recognized, but our understanding of how the fitness effects of infection are distributed across symbiont taxa is limited. In the pea aphid, some of the seven known species of facultative symbionts influence their host's resistance to natural enemies, including parasitoid wasps and a pathogenic fungus. Here we show that protection against this entomopathogen, Pandora neoaphidis, can be conferred by strains of four distantly related symbionts (in the genera Regiella, Rickettsia, Rickettsiella and Spiroplasma). They reduce mortality and also decrease fungal sporulation on dead aphids which may help protect nearby genetically identical insects. Pea aphids thus obtain protection from natural enemies through association with a wider range of microbial associates than has previously been thought. Providing resistance against natural enemies appears to be a particularly common way for facultative endosymbionts to increase in frequency within host populations.     

Prospects for the Management of Invasive Alien Weeds Using Co-Evolved Fungal Pathogens: A Latin American Perspective

Invasive alien weeds pose a serious threat to the biodiversity of natural ecosystems and a significant constraint to agricultural production worldwide. The use of co-evolved natural enemies, a strategy referred to as classical biological control (CBC), has proven to be a potentially efficacious, cost-effective, and safe option for the management of alien weeds. An analysis of CBC of invasive weeds in Latin America is presented, which shows that only 5% of the worldwide releases of agents, overwhelmingly arthropod, have been in this region. Fungal pathogens are increasingly being considered in CBC programmes, and there are now 11 examples of Latin American fungi having been released as biocontrol agents in other regions of the world. In contrast, only three weed pathogens have been deliberately released in the region. Possible reasons for the paucity of CBC programmes in Latin America are presented, despite the presence of a significant number of alien weed species (60 are listed). An analysis of these weeds reveals that many of them could be amenable to control using natural enemies, including nine weed species for which CBC programmes have been successfully implemented elsewhere in the world. In addition, for many of these 60 species, a co-evolved and damaging mycobiota has already been recorded. The prospects for management of invasive alien weeds in Latin America, using co-evolved fungal pathogens, are assessed with particular reference to selected species from the genera Ambrosia, Broussonetia, Calotropis, Commelina, Cyperus, Dichrostachys, Echinochloa, Pittosporum, Rottboellia, Rubus, Sonchus and Ulex. This revised version was published online in July 2006 with corrections to the Cover Date.     

Identification and expression studies of a catalase and a bifunctional catalase-peroxidase in Frankia strain R43

This study investigated the uptake of ¹³⁴Cs by Lactuca sativaL., Silybum marianumGaertn., Centaurea cyanusL., Carthamus tinctorius L. from the Asteraceae, and Beta vulgaris L. var. `Lutiancai' and Beta vulgaris L. var. `Hongtiancai' from the Chenopodiaceae grown in two widely-distributed soils (a paddy soil and a red soil) in South China. The results showed that the plants growing on the paddy soil had a relatively high yield and low [¹³⁴Cs] while those growing on the red soil showed the opposite trend. The accumulation of ¹³⁴Cs was dependent on plant species and soil types. For the paddy soil, mean values for [¹³⁴Cs] were higher for the species of the Asteraceae (ranging from 165 to 185 Bq g^–1) than for those of the Chenopodiaceae (less than 140 Bq g^–1). For the red soil, S. marianumand C. cyanus of the Asteraceae had high average concentrations of ¹³⁴Cs ranging from 340 to 400 Bq g^–1 but L. sativa and C. tinctorius from the same family had low concentrations of ¹³⁴Cs ranging from 115 to 200 Bq g^–1 on a dry weight basis. B. vulgaris L. var. `Lutiancai' and Beta vulgaris L. var. `Hongtiancai' accumulated from 120 to 231 Bq ¹³⁴Cs g^–1 of plant shoot. The transfer factor values of ¹³⁴Cs for the studied species were in general higher in red soil than in paddy soil except C. tinctorius. All plant species from the Asteraceae family growing on the paddy soil had higher transfer factors than the B. vulgaris species. S. marianum, and C. cyanus growing on the red soil had TFs >1, being much higher than the B. vulgaris species. The results therefore showed that the plant species from the Asteraceae could accumulate higher concentrations of radiocesium than the Beta vulgaristhat has previously been suggested as a candidate for phytoremediation of radiocesium contaminated soils.     

Field and laboratory studies to determine the suitability of Cissoanthonomus tuberculipennis (Coleoptera: Curculionidae) for release against Cardiospermum grandiflorum (Sapindaceae) in South Africa

Cardiospermum grandiflorum is an invasive creeper that was targeted for biological control in South Africa in 2003. To determine ecological host range of its natural enemies, surveys were conducted on C. grandiflorum and 11 other Sapindaceae at 40 sites in the weed's native range (Argentina). These surveys indicated that the seed-feeding weevil Cissoanthonomus tuberculipennis was restricted to C. grandiflorum, and that it was among the common natural enemies, occurring at most sites where C. grandiflorum was recorded. Open-field tests were conducted under natural conditions in Argentina to determine the host preference of C. tuberculipennis and other natural enemies of C. grandiflorum among three Cardiospermum species. These tests revealed that C. tuberculipennis and the bug Gargaphia sp. were restricted to C. grandiflorum though the latter subsequently developed on non-target Cardiospermum species in the laboratory. C. tuberculipennis was found to be highly damaging, destroying up to 44% of the seeds per plant in Argentina. In all the host-specificity tests, including no-choice, paired-choice and multi-choice tests, C. tuberculipennis only fed and developed on C. grandiflorum. Failure of C. tuberculipennis to feed and develop on all congeners of C. grandiflorum shows that the weevil is highly host-specific to the target weed. Results of host-specificity tests, open field tests and long-term monitoring of C. tuberculipennis populations demonstrate that the weevil poses no threat to non-target plant species, and therefore safe for release against C. grandiflorum in South Africa. Permission to release C. tuberculipennis in South Africa has been granted by the relevant regulatory authorities.     

Status, invasiveness and environmental threats of three tropical American invasive weeds (Parthenium hysterophorus L., Ageratum conyzoides L., Lantana camara L.) in India

Invasive weeds have threatened the integrity of ecosystems throughout the world. They affect not only the species diversity of native areas but also their biological integrity. In India, a number of invasive exotic weeds have been reported but some viz. Parthenium hysterophorus, Lantana camara and Ageratum conyzoides, especially those from tropical America are troublesome and have caused adverse ecological, economic and social impact. These weeds can be seen growing in different landscapes but are luxuriantly localized in unattended forests and cultivated areas. Parthenium hysterophorus (Asteraceae, commonly known as congress grass) is perhaps the most troublesome and noxious weed of urban and rural India. Besides rapidly colonizing areas replacing the native vegetation, it is also known to cause a number of human health problems such as skin allergy, rhinitis and irritation to eyes of the residents in the vicinity. Likewise, it causes fodder scarcity in addition to being unpalatable and toxic to livestock. Lantana camara (Verbenaceae), another serious tropical American pest, has encroached upon large areas of land, especially the forests where it has virtually replaced the forest floor vegetation and reduced tree growth. Also because of its bushy and spreading type of growth it obstructs forest operations. The third weed, Ageratum conyzoides (Asteraceae, Billy goat weed) has invaded agricultural fields. It interferes with crops and causes yield reductions of major staple crops of India. When it invades rangeland areas, it out competes native grasses causing scarcity of fodder. These weeds have similar growth strategies such as fast growth rates, short life-cycles, greater reproductive potential, high competitive abilities and allelopathy that make them successful invaders of native habitats. Mechanical, chemical, biological and cultural control tactics have failed individually, though integrated approaches combining all these approaches along with community participation and proper land management have been relatively successful. This paper presents various aspects of biology, ecology, hazards and control measures of these weeds.     

Mycorrhiza modulates aboveground tri‐trophic interactions to the fitness benefit of its host plant

1. Arbuscular mycorrhiza (AM), the association of AM fungi and plant roots, may alter morphological and physiological attributes of aboveground plant parts and thereby influence plant‐associated organisms such as herbivores and their natural enemies, predators and parasitoids. 2. The interactions between AM and the players of aboveground tri‐trophic systems have mainly been considered in isolation from each other. The effects of AM on aboveground herbivore–carnivore population dynamics and the consequences to plant fitness are unknown. 3. We explored AM‐induced compensatory mechanisms for AM‐promoted proliferation of the herbivorous spider mite, Tetranychus urticae Koch, on whole bean plants, Phaseolus vulgaris L. Vegetative and reproductive plant growth, AM fungal colonisation levels, and mite densities were assessed on spider mite‐infested plants colonised or not by the AM fungus Glomus mosseae Nicol. & Gerd, and harbouring the natural enemy of the spider mites, the predatory mite Phytoseiulus persimilis Anthias‐Henriot or not. 4. AM symbiosis modulated the aboveground tri‐trophic system to the fitness benefit of the plant. AM‐increased plant productivity outweighed the fitness decrease due to AM‐promoted herbivory: at similar vegetative growth, mycorrhizal plants produced more seeds than non‐mycorrhizal plants. 5. AM‐increased spider mite population levels were compensated for by enhanced population growth of the predators and increased plant tolerance to herbivory. 6. AM‐enhanced predator performance looped back to the AM fungus and stabilised its root colonisation levels, providing the first experimental evidence of a mutually beneficial interaction between AM and an aboveground third trophic level natural enemy.     

Fusarium nygamai, a potential bioherbicide for Striga hermonthica control in sorghum

Glasshouse trials were performed to investigate the control of the parasitic weed Striga hermonthica by Fusarium nygamai and the performance of the host plant sorghum (Sorghum bicolor) using different inoculum substrates and inoculum amounts of the fungus. Optimal constant and alternating temperatures for the growth of the fungus were 25°C and 30/20°C, respectively. Striga incidence was decreased up to 100% when the fungus was incorporated into the soil preplanting. Emerged Striga plants at different stages of growth up to the flowering stage were killed by the fungus when the fungus was applied postemergent. In root-chamber trials none of the Striga seeds germinated when 10 ml inoculum suspension of 8 × 10⁶ spores/ml of F. nygamai was applied on seeds of the parasitic weed sprinkled on the surface of filter paper. F. nygamai has potential as a bioherbicide for Striga control. Further studies regarding its performance under field conditions and its safety to the environment and humans should be assessed.     

Are Ericoid Mycorrhizas a Factor in the Success of Calluna vulgaris Heathland Restoration?

Methods used in the restoration of lowland heath vary depending on edaphic factors at a site and need for introduction of ericaceous propagules. This study investigates the effect of some methods on growth of an important ericaceous species, Heather (Calluna vulgaris). It also explores whether success of growth of C. vulgaris in restoration schemes is affected by its degree of colonization by ericoid mycorrhizal fungi (ERM). The success of Heather growth was compared at three sites, a control area of natural heathland and two restoration sites. These were a quarry where soil had been translocated but not chemically manipulated and a site on agricultural land where the top soil had been improved but then either stripped away or acidified prior to attempting heathland restoration. Propagules of C. vulgaris were applied either as turves or as clippings. Results show that clippings produced as dense a cover of C. vulgaris as turves over a period of 13 years and that plants in such swards can exhibit a degree of ERM colonization comparable to that found in mature plants growing in natural heathland. Young (<2 years of age) plants of C. vulgaris had less extensive mycorrhizal colonization of their roots, particularly when growing on restored agricultural soils. A relationship was found between lower levels of mycorrhizal colonization and smaller aboveground plant growth. Success of heathland restoration may be improved by finding means to enhance the rate and extent of mycorrhizal colonization of young C. vulgaris growing in a restoration environment.     

Natural enemies ofChenopodium spp. in Pakistan with notes onTrioza Chenopodii [Hem.: Psyllidae], a promising biocontrol agent

Investigations on the natural enemies ofChenopodium spp. in Pakistan showed that 40 insects and a fungus were associated with this weed. Of these, 3 insects,Trioza chenopodii Reuter,Gasteroclisus auriculatus Sahlb.Hayhustria? atriplicis (L.) and a fungusPhysoderma pulposum have some potential as beneficial control agents.T. chenopodii was the most effective destroyer of the weed. It developed 5 generations per year and was restricted to the generaChenopodium, Atriplex andHalimione.     

Assessing the biological control of yellow starthistle (Centaurea solstitialis L): prospective analysis of the impact of the rosette weevil (Ceratapion basicorne (Illiger))

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Adjuvants enhance the biological control potential of an isolate of Colletotrichum gloeosporioides for biological control of sicklepod (Senna obtusifolia)

In greenhouse experiments, unrefined corn oil, Silwet L-77, and an invert emulsion were tested as adjuvants with the mycoherbicidal fungus Colletotrichum gloeosporioides, a weakly virulent pathogen of sicklepod (Senna obtusifolia). A 1:1 (v/v) fungus/corn oil tank mixture containing 0.2% (v/v) Silwet L-77 surfactant reduced the dew period requirements for maximum weed infection and mortality from 16 to 8 h, and delayed the need for free moisture for greater than 48 h. This formulation also resulted in the ability of the pathogen to infect and kill weeds in larger (>5 leaf) growth stages. The invert emulsion resulted in similar effects upon these parameters. These results suggest that invert emulsions, unrefined corn oil and Silwet L-77 surfactant greatly improve the bioherbicidal potential of this pathogen for control of sicklepod, a serious weed pest in the southeastern US.     

Searching for weed biocontrol agents—when to move on?

‘Classical’ biological control for an exotic weed requires time‐consuming and expensive surveys for natural enemies in the weed's native range. We advocate the use of rarefaction curves to improve survey efficiency, i.e. to determine the minimum sampling effort for discovering most of the potential control agents actually occurring in the weed's native range. Rarefaction (dilution) curves can be used to estimate the number of herbivore species expected on a given number of plants, at sampling sites or regions, using presence/absence data and species frequencies. An analysis of the shape of the rarefaction curves will therefore indicate (a) which sites possibly contain more undiscovered herbivore species and (b) whether sampling new sites is more likely to reveal further herbivores. This approach is illustrated with two case studies of insect surveys, of root and flower head feeders on Centaurea maculosa (Asteraceae) in Europe and for flower head feeders of various Asteraceae in Brazil. Finally, we consider consequences of combining this approach with focussed searches in the centre of endemism and propose a general survey protocol for natural enemies associated with a host plant in its native range.     

Inadvertent biological control: an Australian thrips killing an invasive New Zealand tree in California

Transport hubs of international trade and tourism are sites of unprecedented long-distance dispersal of species and novel ecological interactions. In cases of invasive plants released from their specialist natural enemies, novel interactions with both resident enemies and new arrivals can accumulate and potentially reduce weed competitiveness. I present here one dramatic example of this, where an invasive woody weed in southern California is being rapidly controlled by an accidentally introduced genus-specialist herbivorous insect. The New Zealand native shrub/small tree, Myoporum laetum, is a long-time popular ornamental plant in California and has become an invasive woody weed. In 2005, a Myoporum-specific thrips, Klambothrips myopori, was discovered (and described) in California feeding on M. laetum leaves. Several searches have failed to find K. myopori in New Zealand and a population has recently been discovered in Tasmania, Australia, feeding on Myoporum insulare. In 5 years, K. myopori has killed off about half of southern Californian M. laetum with almost all surviving individuals being gradually defoliated. Inadequate border biosecurity has resulted in inadvertent biological control, in a rapid timeframe, caused by a novel enemy. Unfortunately, K. myopori has subsequently been accidentally transported from California to Hawaii where it is now killing off Hawaiian native Myoporum sandwicense. Transport hubs can both connect weeds with natural enemies and disperse those enemies more widely.     

Evaluation of the field impact of an adventitious herbivore on an invasive plant,yellow toadflax,in Colorado,USA

Although some introduced plants arrive into their new range without their generalist and specialist herbivores, for others, their herbivores arrive prior to, with, or after the introduction of the plant, reestablishing the link between natural enemies and invaders in the introduced range. Research documenting the effects of adventitiously introduced herbivores on their target plants in the introduced range, and the mechanisms by which those effects occur, can provide insight into potential biological weed control. We studied the effects of an accidentally introduced beetle Brachypterolus pulicarius on the growth and reproduction of its host, the invasive plant Linaria vulgaris (yellow toadflax), growing under field conditions across multiple years and sites in western Colorado, USA. We found that feeding by B. pulicarius on L. vulgaris was variable among 3 years (2002–2004) and across eight local sites. Part of the variation in damage was explained by ramet density; sites with greater ramet density experienced a higher proportion of damage. In an observational study across 2 years, damage was positively correlated with estimates of sexual reproduction, ramet growth, and clonal shoot production. However, opposite trends were observed in an experiment; damage by B. pulicarius decreased estimates of sexual reproduction. Differences between the results of the observational and experimental studies were likely driven by selective feeding by B. pulicarius on larger ramets. Nonetheless, the ability of B. pulicarius to control established L. vulgaris population growth remains uncertain under the environmental conditions we studied. In both the observational and experimental study, B. pulicarius did not affect L. vulgaris survival, and we found no evidence that established L. vulgaris populations were seed limited, suggesting that reductions in seeds may not translate into demographic changes in heavily infested populations. Interactions among insect foraging behavior, individual plant responses to damage, and the demographic consequences of seed input may help to explain the varying degrees to which herbivores affect plants and populations in this and other systems.