Article

Reducing the fitness of an invasive weed, Parthenium hysterophorus: Complementing biological control with plant competition

Authors:
  • The University of Agriculture, Peshawar, Pakistan (formerly North West Fronteir Province Agriculture University/Khyber Pakhtunkhwa Agriculture Peshawar Pakistan
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

We studied the effects of a biological control agent, Epiblema strenuana Walker (Lepidoptera: Tortricidae) alone and together with a sown native grass, Astrebla squarrosa C.E. Hubb. and an introduced pasture plant, Clitoria ternatea L. on growth and seed production of Parthenium hysterophorus L. Astrebla squarrosa and C. ternatea individually reduced shoot dry biomass of P. hysterophorus by 30 and 42%, respectively; and by 48 and 70%, respectively in the presence of biological control agent, E. strenuana. Similarly, A. squarrosa and C. ternatea individually reduced weed seed production up to 48 and 64%, respectively; and by 73 and 81%, respectively in the presence of E. strenuana. In the presence of E. strenuana, the biomass of A. squarrosa and C. ternatea was increased by 13 and 10%, respectively. The biological control agent induced more galls per P. hysterophorus plant when either of the competing plants were present than when grown alone. The abundance of galls increased with pasture competition, but only for C. ternatea, and not for A. squarrosa. The biological control agent worked synergistically with the two competitive plants to reduce the growth and production of viable seed, which should lead to a decrease in the P. hysterophorus soil seed banks in the field, and eventually seedling recruitment in future generations of P. hysterophorus.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Whereas the lower levels of P. hysterophorus invasion documented within the understocked site, may be attributed to the reserve's recent approach towards reducing grazer numbers, which promotes and aids in pasture recovery (Strathie and McConnachie, 2019). These differing stocking levels also affect the competitive ability of pastures and their species (Riginos, 2009;Frankow-Lindberg, 2012;Van Oudtshoorn, 2012;Shabbir et al., 2020), likely accounting for the differences documented in P. hysterophorus invasions observed within the plots at the over-and understocked reserves. ...
... These losses in below-ground species diversity suggest that the regenerative capacity of native species in the overstocked reserve may be deteriorating as a result of continued P. hysterophorus invasion (Navie and Rogers, 1997;Navie et al., 2004;Cowie et al. 2021), creating an 'invasion trap'. Whereas findings from the understocked reserve support the notion that seedbank communities can begin recovering from P. hysterophorus invasion following the implementation of and adherence to management practices, that aid in the recovery of vegetation above-ground (Strathie and McConnachie, 2019;Khan et al., 2019;Shabbir et al., 2020). Increases in species richness and evenness, at the understocked reserve, indicate the recruitment of species within the local seedbank and a corresponding loss in dominance by P. hysterophorus (Nigatu et al., 2010;Belgeri et al., 2014). ...
... Overall, the declines in P. hysterophorus and its seedbank, under understocked conditions shows promise in limiting the invasion of P. hysterophorus. However, reducing stocking densities alone is unlikely to completely displace or control the weed, advocating for the integration of management practices with other control programmes such as biological Cowie et al., 2019) and/or chemical controls (Belgeri et al., 2014;Cowie et al., 2020b;Shabbir et al., 2020). ...
Article
Parthenium hysterophorus L. (Asteraceae) is a noxious, annual invasive herb prevalent in more than 50 countries worldwide. In South Africa, the weed is a highly damaging invasive species, particularly in savanna regions, threatening food security, native biodiversity, livelihoods and human health. Given the multitude of threats posed by P. hysterophorus, this study aimed to determine the influence of the invasion of P. hysterophorus and its associated seedbank dynamics at a small spatial scale. To assess this, two neighbouring savanna reserves, with differing stocking densities (i.e. over- and understocked), were selected and assessed seasonally over a four-year period. Overstocking exacerbated the invasion of P. hysterophorus, with greater densities, larger plants and increased seed production, at a plot level. This enhanced invasion was also reflected in changes to the site's above-ground plant community, with significantly lower species richness, evenness, and diversity. Parthenium hysterophorus comprised more than 80% of the overstocked reserve's seedbank, and was responsible for continued declines in the richness, evenness and diversity of species below-ground. Whereas P. hysterophorus at the understocked reserve, occupied a smaller proportion of the seedbank (∼70%), with richness, evenness and diversity all showing signs of recovery over the four-year period. Overall, this research highlighted the impacts of P. hysterophorus in South Africa, as well as the potential role grazing management has in limiting or facilitating P. hysterophorus invasions and their impacts within savannas.
... Maintaining a healthy and competitive pasture is considered a useful approach, particularly as part of an integrated strategy to manage Navua sedge in grazed areas (Karan, 1976;Mune, 1959;Shi et al., 2021;Vitelli et al., 2010;Vogler et al., 2015). Hence, exploring the use of desirable pasture grasses that can compete with Navua sedge under varying ecological/ land use scenarios will be informative and could offer long term control of the Navua sedge weed, especially when combined with biological and/or chemical control options (Shabbir et al., 2020). ...
... In summary, grazing appears to counteract the competitive effect on Navua sedge, and hence grazing management should be prioritized once the pasture replacement with Rhodes grass is initiated. Furthermore, the choice of a competitive pasture plants can be complemented with biological control agents feeding on the sedge weed to enhance further the pasture species competitive ability and offer a better integrated weed management option (Shabbir et al., 2020). ...
Article
Full-text available
Navua sedge (Cyperus aromaticus), a perennial monocot plant native to tropical Africa, is a major weed in pasture and cropping areas in the wet tropical regions of Australia and South Pacific countries. In grazing pasture lands, rapid growth and reproduction of unpalatable Navua sedge leads to displacement of co-occurring pasture species and depletion of livestock carrying capacity and production. Understanding the interspecific competitive ability of Navua sedge with co-occurring desirable grasses and in response to varying ecological scenarios (e.g., grazing and plant density) is critical for the management of the weed in pasture situations. In a glasshouse setting, two co-occurring pasture species-humidicola (Urochloa humidicola) and Rhodes grass (Chloris gayana) were grown with Navua sedge, in pots using a replacement series model. For each Navua sedge weed-pasture species pair, the experimental setup comprised of four ratios in two densities under simulated grazing and nongrazing conditions of the pasture grasses. Navua sedge growth and reproduction was highest when it grew as a monoculture or when co-occurring pastures were exposed to simulated grazing as this action, reduced the competitiveness of the pasture grasses. Overall and using biomass gained, tiller production and relative yield as indices of growth dynamics, Rhodes grass was more competitive against Navua sedge than humidicola in both grazed and nongrazed conditions especially under high plant density. These results suggest the potential to include competitive pastures in integrated management strategies for Navua sedge, but species selection and grazing practices may influence the effectiveness of this approach.
... And in case of cropped land, one can also spray 1% glyphosate solution in Parthenium infested field [62]. Recently Shabbir et al. (2020) showed biological agent when combined with competitive plant like C.ternatea and Asterbla squarrosa could result into reduction of dry biomass from shoots and also reduction in seed banks with simultaneous decrease into the seedling recruitment in case of upcoming generation [63]. The drawback behind the use of herbicide is pollution and imbalance in ecosystem. ...
... And in case of cropped land, one can also spray 1% glyphosate solution in Parthenium infested field [62]. Recently Shabbir et al. (2020) showed biological agent when combined with competitive plant like C.ternatea and Asterbla squarrosa could result into reduction of dry biomass from shoots and also reduction in seed banks with simultaneous decrease into the seedling recruitment in case of upcoming generation [63]. The drawback behind the use of herbicide is pollution and imbalance in ecosystem. ...
Article
Full-text available
Parthenium hysterophorus known for its proliferative capacity has run wild through many countries over the globe. It has a significant impact in America, India, Australia, and Africa. It has the potential to cause a huge economic loss to the country in the form of crop damage, influencing the health of humans as well as of livestock. Today it is considered one of the seven most noxious weeds in the world. It is an annual herb that has been native to northern Mexico as well as the U.S.A. It has been known for producing thousands of rosettes responsible for toxicity and its rapid spreading over a region. There has been a huge loss in crop yield due to either direct competition or due to allelopathy. There are various methods to tackle its uncontrolled growth such as burning, spraying herbicides, biological control in the form of introducing various insects like Zygogramma bicolorata, Epiblema strenuana, etc. In the last few decades lot of beneficial prospects have been developed with the involvement of Parthenium hysterophorus. It has been used in traditional medicine to treat conditions like inflammation, pain, fever, and diseases like malaria, dysentery, etc. It can be used to produce biogas, enzymes and could also take upon heavy metal pollution and acts as a bioremediation agent. It can also be used in dye removal and also be used in the removal of various menace causing aquatic weeds. It has been proved to be useful in order to maintain the moisture of the field and could potentially be used as organic manure. It is proved to be better than NPK synthetic fertilizers, provided optimum conditions have been met. The aim of this review article is to explore various dimensions of Parthenium existence and how its uncontrolled growth could be tackled.
... However, the sowing and establishment of palatable grasses, such as these, can easily be hindered if stocking rates and grazing pressure are too high, limiting pasture regrowth (Van Oudtshoorn, 2015;Khan et al., 2019). This suggests that sowing native grass seed into P. hysterophorus invaded areas with low levels of grazing pressure, may help to mitigate degradation caused by overgrazing and invasion (Strathie and McConnachie, 2019;Shabbir et al., 2020). ...
... Likewise, the loss of perennial grasses, and their associated levels of competition, within the cleared only plots likely permitted increases in the growth of P. hysterophorus. Decreases in the reproductive capacity of P. hysterophorus within the sown as well as the sown and cleared plots is most likely to have arisen from the limited resources available (Cowie et al., 2019;Khan et al., 2019;Shabbir et al., 2020). However, P. hysterophorus still produced an abundance of seed, despite suffering reductions in vegetative growth and resource availability. ...
Article
The annual herb Parthenium hysterophorus L. (Asteraceae), remains one of Southern Africa's most significant invasive weeds, commonly invading savannas, and their rangelands, causing severe losses to agriculture, livestock production and native biodiversity. Previous studies have suggested that perennial grasses may act as useful competitive species, capable of suppressing the growth and invasion of P. hysterophorus. To explore this, a total of 48 plots were established within an invaded savanna, using a randomised block design, and included treatments with and without the clearing of P. hysterophorus, as well as with and without the sowing of native perennial grass seed (Anthephora pubescens, Chloris gayana, Cynodon dactylon, Digitaria eriantha, Eragrostis curvula, Panicum maximum and Themeda triandra). Plots were assessed yearly in terms of P. hysterophorus density and growth as well as grass species composition, basal cover, and biomass over a three-year period. Clearing alone was found to exacerbate invasion, increasing P. hysterophorus density by 40%. Whereas the sowing of grass seed, in both the cleared and uncleared plots, increased the abundance of perennial grass species by 28%, subsequently reducing the size, reproductive output and density of P. hysterophorus over the three years. In addition, these sowing efforts contributed towards partial restoration of the plots, enhancing grass basal cover by ~15% and biomass production by 17%. Overall, this research suggests that sowing of native grass species, with or without clearing, may be a useful supplementary control or restoration tool towards the long-term management of P. hysterophorus invasions in managed savannas and rangelands in Southern Africa.
... For instance, Parthenium hysterophorus causes approximately 110 million dollars losses on a yearly basis in Australia. 14 In the UK and USA, losses due to IPS exceed 400 million pounds 15 and 23 billion dollars per year, respectively. 16 A harmful IPS has the capacity to become acclimatized in many habitats. ...
Article
Invasive plant species (IPS) are often considered weeds that cause high yield losses in crops, negatively affect the environment, and disrupt certain ecosystem services. The negative impact of IPS on biodiversity is increasing and disturbing native vegetation. The management of plant invasions can be divided in two phases (before and after invasion). Prior to introduction it is crucial to develop the knowledge base (biology, ecology, distribution, impact, management) on IPS, prevention measures and risk assessment. After introduction if eradication fails, the monitoring and the integrated management of IPS are imperative to prevent the naturalization and further dispersal. This review uses two major invasive weed species (Amaranthus palmeri S. Wats. and Solanum elaeagnifolium Cav.) as case studies to propose a framework for early detection, rapid herbicide resistance screening, and integrated management. The holistic framework that is presented exploits recent: (i) novel detection tools, (ii) rapid tests and assays for herbicide resistance, and (iii) biology, ecology, distribution traits, and management tools for the IPS. Farmers, advisors, researchers, and policymakers need briefing on IPS growth dynamics, adaptability rates, and response to conventional and novel treatments to prevent new invasions, eradicate isolated stands, and mitigate the impact of invasive weed species in the long-term.
Preprint
Full-text available
Predicting invasion success requires understanding how abiotic and biotic factors in the local environment interact with the particular traits of potential invaders. Relative to studies of direct antagonistic effects, fewer studies have examined how positive species interactions, such as facilitation or mutualism, or indirect interactions in multispecies communities, can affect invasion success. We examined the effects of drought and mutualisms with rhizobia bacteria on the performance of a widely invasive legume, Medicago polymorpha. In a greenhouse experiment, we found that watering regime affected plant performance, but non-linear patterns in response to decreasing water were dependent on the specific plant genotype. In a second experiment, we found that the effects of drought on plant performance were dependent on the presence of rhizobia, particularly for genotypes collected from the invasive range. This suggests that indirect ecological effects may have important consequences for invasion success. We contextualize the strength of these direct and indirect effects by comparing this study to effect sizes in other studies of the same species. In this species, predicting invasion into a natural community context will require understanding multiple direct and indirect effects in the local environment, as well as their effects on the specific genetic composition of the invading population.
Chapter
Parthenium hysterophorus is an invasive weed species, indigenous to the Americas. It has spread into 50 tropical and subtropical countries in Asia, Oceania, and Africa. After establishing its dominion in the introduced ranges, it is now posing as a severe threat to their agricultural production and biodiversity. The rampant spread of the weed is due to its intrinsic invasive abilities, for example, proficient reproductive ability, unique seed biology, phytotoxicity, plasticity, and unpalatability. Attempts have been made to manage the weed using mechanical, chemical, and biological methods, but a lack of constant efforts results in its unchecked growth. With ongoing climatic changes, the weed is expected to expand its invasion range. It is, therefore, crucial to reassess the core invasive characteristics of the weed, especially the behavioral changes in response to climate change. An appraisal of loopholes in current management practices and new directives for the betterment of these practices is also required.
Article
Full-text available
Parthenium weed has been invading native and managed Australian grasslands for almost 40 years. This study quantified the potential of selected plant mixtures to suppress the growth of parthenium weed and followed their response to grazing and their impact upon plant community diversity. The first mixture consisted of predominantly introduced species including Rhodes grass, Bisset bluegrass, butterfly pea and green panic. This mixture produced biomass rapidly and showed tolerance to weed species other than parthenium weed. However, the mixture was unable to suppress the growth of parthenium weed. The second mixture of predominantly native pasture species (including forest bluegrass, Queensland bluegrass, Buffel grass and siratro) produced biomass relatively slowly, but eventually reached the same biomass production as the first mixture 12 weeks after planting. This mixture suppressed parthenium weed re-establishment by 78% compared to the control treatment. Its tolerance to the invasion of other weed species and the maintenance of forage species evenness was also superior. The total diversity was five times higher for the mixture communities as compared to the plant community in the control treatment. Therefore, using the suppressive pasture mixtures may provide an improved sustainable management approach for parthenium weed in grasslands.
Article
Parthenium weed (Parthenium hysterophorus) is a highly invasive plant that has invaded many parts of world including Australia. The present study reports on the effects of rising [CO2] on the performance of one of its biological control agents, stem-galling moth (Epiblema strenuana) when combined with a competitive plant, buffel grass (Cenchrus cilliaris). The study was carried out under controlled environment facilities during 2010-11. P. hysterophorus when grown under elevated [CO2] of 550 µmol mol⁻¹, produced a greater biomass (27%), attained greater stature (31%), produced more branches (45%) and seeds plant⁻¹ (20%), than those grown at ambient [CO2] of 380 µmol mol⁻¹. Buffel grass reduced the biomass and seed production of P. hysterophorus plants by 33% and 22% under ambient [CO2] and by 19% and 17% under elevated [CO2], respectively. The combined effect of buffel grass and E. strenuana reduced dry biomass and seed production by 42% and 72% under ambient [CO2] and 29% and 37% elevated [CO2], respectively. Although the suppressive effect was different between ambient and elevated [CO2], the effect is likely to be retained. Stem gall formation by E. strenuana significantly enhanced the lateral branch production in plants grown under both [CO2]. Epiblema strenuana did not reduce the seed production of P. hysterophorus under the elevated [CO2] nevertheless, our earlier study had confirmed that many of the seeds produced under such conditions are not filled. This study has highlighted that the additive suppressive effect of E. strenuana and buffel grass on P. hysterophorus growth would be retained under future atmospheric CO2 enrichment.
Article
Full-text available
Main conclusion This review provides an insight into alien plant invasion taking into account the invasion mechanism of parthenium weed (Parthenium hysterophorusL.). A multi-lateral understanding of the invasion biology of this weed has pragmatic implications for weed ecology and management. Biological invasions are one of the major drivers of restructuring and malfunctioning of ecosystems. Invasive plant species not only change the dynamics of species composition and biodiversity but also hinder the system productivity and efficiency in invaded regions. Parthenium weed, a well-known noxious invasive species, has invaded diverse climatic and biogeographic regions in more than 40 countries across five continents. Efforts are under way to minimize the parthenium weed-induced environmental, agricultural, social, and economic impacts. However, insufficient information regarding its invasion mechanism and interference with ecosystem stability is available. It is hard to devise effective management strategies without understanding the invasion process. Here, we reviewed the mechanism of parthenium weed invasion. Our main conclusions are: (1) morphological advantages, unique reproductive biology, competitive ability, escape from natural enemies in non-native regions, and a C3/C4 photosynthesis are all likely to be involved in parthenium weed invasiveness. (2) Tolerance to abiotic stresses and ability to grow in wide range of edaphic conditions are thought to be additional invasion tools on a physiological front. (3) An allelopathic potential of parthenium weed against crop, weed and pasture species, with multiple modes of allelochemical expression, may also be responsible for its invasion success. Moreover, the release of novel allelochemicals in non-native environments might have a pivotal role in parthenium weed invasion. (4) Genetic diversity found among different populations and biotypes of parthenium weed, based on geographic, edaphic, climatic, and ecological ranges, might also be a strong contributor towards its invasion success. (5) Rising temperatures and atmospheric carbon dioxide (CO2) concentrations and changing rainfall patterns, all within the present day climate change prediction range are favorable for parthenium weed growth, its reproductive output, and therefore its future spread and infestation. (6) Parthenium weed invasion in South Asia depicts the relative and overlapping contribution of all the above-mentioned mechanisms. Such an understanding of the core phenomena regulating the invasion biology has pragmatic implications for its management. A better understanding of the interaction of physiological processes, ecological functions, and genetic makeup within a range of environments may help to devise appropriate management strategies for parthenium weed.
Article
Full-text available
Pest Risk Assessments (PRAs) routinely employ climatic niche models to identify endangered areas. Typically, these models consider only climatic factors, ignoring the 'Swiss Cheese' nature of species ranges due to the interplay of climatic and habitat factors. As part of a PRA conducted for the European and Mediterranean Plant Protection Organization, we developed a climatic niche model for Parthenium hysterophorus, explicitly including the effects of irrigation where it was known to be practiced. We then downscaled the climatic risk model using two different methods to identify the suitable habitat types: expert opinion (following the EPPO PRA guidelines) and inferred from the global spatial distribution. The PRA revealed a substantial risk to the EPPO region and Central and Western Africa, highlighting the desirability of avoiding an invasion by P. hysterophorus. We also consider the effects of climate change on the modelled risks. The climate change scenario indicated the risk of substantial further spread of P. hysterophorus in temperate northern hemisphere regions (North America, Europe and the northern Middle East), and also high elevation equatorial regions (Western Brazil, Central Africa, and South East Asia) if minimum temperatures increase substantially. Downscaling the climate model using habitat factors resulted in substantial (approximately 22-53%) reductions in the areas estimated to be endangered. Applying expert assessments as to suitable habitat classes resulted in the greatest reduction in the estimated endangered area, whereas inferring suitable habitats factors from distribution data identified more land use classes and a larger endangered area. Despite some scaling issues with using a globally conformal Land Use Systems dataset, the inferential downscaling method shows promise as a routine addition to the PRA toolkit, as either a direct model component, or simply as a means of better informing an expert assessment of the suitable habitat types.
Conference Paper
Full-text available
This paper details aspects of the continued successful eradication of parthenium weed from New South Wales (NSW). Parthenium weed is one of the 20 Australian Weeds of National Significance and is increasingly problematic in central and southern Queensland (Qld). The species decreases the viability of livestock production, harbours plant disease, and causes health problems in humans. Parthenium weed was first detected in NSW in 1982. Since that time there have been numerous detections (usually small numbers of plants) and subsequent eradications. Strong legislative, extension and management processes have supported this eradication program. The state of NSW covers in excess of 800,000 km2. There are no geographic or artificial borders stopping the spread of any weed between NSW and Qld. On the contrary, there are many opportunities for weed seed spread between the two states, both via natural means and via vehicular and harvest machinery movement. This simple fact highlights the remarkable success of the NSW parthenium eradication campaign. It also highlights that containment of weeds to one area of a contiguous land mass, and eradication from other areas is possible. The factors responsible for this success are examined and discussed.
Article
Full-text available
A significantly increased water regime can lead to inundation of rivers, creeks and surrounding flood-plains-and thus impact on the temporal dynamics of both the extant vegetation and the dormant, but viable soil-seed bank of riparian corridors. The study docu-mented changes in the soil seed-bank along riparian corridors before and after a major flood event in January 2011 in southeast Queensland, Australia. The study site was a major river (the Mooleyember creek) near Roma, Central Queensland impacted by the extreme flood event and where baseline ecological data on riparian seed-bank populations have previously been collected in 2007, 2008 and 2009. After the major flood event, we collected fur-ther soil samples from the same locations in spring/ summer (November–December 2011) and in early au-tumn (March 2012). Thereafter, the soils were exposed to adequate warmth and moisture under glasshouse condi-tions, and emerged seedlings identified taxonomically. Flooding increased seed-bank abundance but decreased its species richness and diversity. However, flood impact was less than that of yearly effect but greater than that of seasonal variation. Seeds of trees and shrubs were few in the soil, and were negatively affected by the flood; those of herbaceous and graminoids were numerous and pro-liferate after the flood. Seed-banks of weedy and/or exotic species were no more affected by the flood than those of native and/or non-invasive species. Overall, the studied riparian zone showed evidence of a quick recovery of its seed-bank over time, and can be consid-ered to be resilient to an extreme flood event.
Article
Full-text available
Parthenium weed, an annual herb native to tropical America, causes severe economic, human, and animal health and environmental impacts in Australia and in many countries in Asia, Africa, and the Pacific. There is little known about variation in reproductive output in naturally occurring populations of this weed. This information is vital to develop plant population models, devise management strategies to reduce seed output, and formulate parthenium weed pollen-induced human health (e.g., dermatitis and hay fever) risk assessment. Here, the variations in the number of capitula produced by the parthenium weed at two sites in Queensland, Australia, over a 4-yr period are reported. Under field conditions, parthenium weed produced up to 39,192 capitula per plant (> 156,768 seeds per plant), with majority of the plants (approximate to 75%) producing between 11 and 1,000 capitula, and less than 0.3% of the plants producing more than 10,000 capitula (> 40,000 seeds per plant). The number of capitula per plant in the field (297 +/- 22) was much lower than those reported from glasshouse and laboratory studies. Plant biomass contributed to 50 to 80% of the variation in capitulum production between plants within plots at each site, and weed density accounted for 62 to 73% of the variation in capitulum production between plots within each site. As plant size is directly correlated with reproductive output, plant size distributions in parthenium weed can be used to estimate effective population size. Information on variation in reproductive output will be used to implement management strategies to reduce parthenium weed seed output, resulting in reduced soil seed bank and weed seed spread.
Article
Full-text available
The North American Epiblema strenuana (Walker) may prove to be an important agent for the control of the weed Parthenium hysterophorus L. in Australia. In this article we report time-related changes in the galled shoots of P. hysterophorus consequent to attack by E. strenuana. In addition to many structural adjustments involving tissue regeneration, the host plant shows a number of metabolic alterations as a result of its response to galling by the moth larva. Through histochemical localization we demonstrate how the plant synthesizes some of the key metabolites facilitating the nutritional requirements of the larva and displays compensatory behavior to neutralize the stress induced by larval feeding. As the larva prepares for pupation, host-plant metabolism changes abruptly, by accumulating polyphenolic materials in the translocatory cells and ultimately blocking them. This event coincides with a modest decline in gall mass that was previously increasing with larval mass. The ability of the moth to damage the growth point, phloem, and the associated parenchyma, making them nonfunctional, and induce the plant to lose vigor, indicates that it is a potential biocontrol agent.
Article
Full-text available
Effects of gall damage by the introduced moth Epiblema strenuana on different growth stages of the weed Parthenium hysterophorus was evaluated in a field cage using potted plants with no competition and in naturally regenerated populations with intraspecific competition. Gall damage at early stages of plant growth reduced the plant height, main stem height, flower production, leaf production, and shoot and root biomass. All galled, potted plants with no competition produced flowers irrespective of the growth stage at which the plants were affected by galling, but lesser than in ungalled plants. Gall induction during early growth stages in field plants experiencing competition prevented 30% of the plants reaching flowering. However, 6% of the field plants escaped from gall damage, as their main stems were less vigorous to sustain the development of galls. Flower production per unit total plant biomass was lower in galled plants than in ungalled plants, and the reduction was more intense when gall damage was initiated at early stages of plant growth. In potted plants with no competition, the number of galls increased with the plant vigour, as the gall insects preferred more vigorous plants. But in field plants there were no relationship between gall abundance and plant vigour, as intraspecific competition enhanced the negative effects of galling by reducing the vigour of the weed.
Article
Full-text available
Gall induction by arthropods results in a range of morphological and physiological changes in their host plants. We examined changes in gas exchange, nutrients, and energetics related to the presence of stem galls on Parthenium hysterophorus L. (Asteraceae) induced by the moth, Epiblema strenuana Walker (Lepidoptera: Tortricidae). We compared the effects of galls on P. hysterophorus in the rosette (young), pre-flowering (mature), and flowering (old) stages. Gall induction reduced the leaf-water potential, especially in flowering stage plants. In young and mature stage plants, galling reduced photosynthetic rates considerably. Gall induction reduced the transpiration rate mostly in mature plants, and this also diminished stomatal conductance. Energy levels in most galls and in shoot tissue immediately below the galls were significantly higher than the energy levels in stem tissue immediately above the galls, indicating that the gall acts as a mobilizing sink for the moth. Galling had significant effects on concentrations of minerals such as boron, chloride, magnesium, and zinc. In galled plants, reduced leaf-water potential and reduced rates of photosynthesis, transpiration, and stomatal conductance may have altered mineral element levels. These observed effects demonstrate that E. strenuana has the potential to regulate P. hysterophorus.
Article
Full-text available
Six species of insects and a rust fungus have been successfully established for biocontrol of the weed Parthenium hysterophorus L. in Queensland, Australia. Effectiveness of biocontrol insects was evaluated at two properties in Queensland during 1996-97 based on an exclusion experiment using insecticides. Parthenium-infested plots with and without biocontrol insects were sampled at monthly intervals and the impact of biocontrol insects on parthenium at individual plant and whole population levels monitored. Biocontrol insects were more effective at Mt Panorama (central Queensland) than at Plain Creek (north Queensland). At Mt Panorama, the leaf-feeding beetle Zygogramma bicolorata Pallister caused 96% defoliation and the stem-galling moth Epiblema strenuana Walker affected 100% of the plants, resulting in reductions of 90% in weed density, 40% in plant height, and 82% in flower production. Exclusion of biocontrol insects resulted in a 52% increase in seedling emergence and a seven-fold increase in the soil seed bank in the following season. At Plain Creek, E. strenuana was the only prominent agent. It affected 92% of the plants and prevented 32% of plants from producing any flowers, reduced plant height by 40% and flower production by 49%, but did not reduce the plant biomass, weed density or soil seed bank. However, exclusion of biocontrol insects resulted in an eight-fold increase in the soil seed bank in the following season.
Article
Full-text available
Variation in the effectiveness of biocontrol agents on the weed Parthenium hysterophorus L. was evaluated at two properties (Mount Panorama and Plain Creek) in Queensland, Australia for four years (1996-2000) using a pesticide exclusion experiment. At Mount Panorama, higher levels of defoliation by the leaf-feeding beetle Zygogramma bicolorata Pallister and galling by the moth Epiblema strenuana Walker in 1996-97 coincided with an above average summer rainfall, but in the following three years with below average summer rainfall the defoliation and galling levels were significantly lower. Biocontrol had significant negative impact on the weed only in 1996-97 with no major impact in the following three years. At Plain Creek, galling by E. strenuana was evident in all the four years, but varied significantly between years due to non-synchrony between P. hysterophorus germination and E. strenuana emergence. At Plain Creek biocontrol had limited impact on the weed in 1996-97 and 1997-98, with no significant impact in the following two years. Over the 4-year period, defoliation and galling resulted in 70% reduction in the soil seed bank at Mount Panorama, but the reduction in the soil seed bank at Plain Creek due to galling was not significant. Effectiveness of Z. bicolorata and E. strenuana was dependent on weather conditions and as a result had only limited impact on the weed in three out of four years.
Article
Parthenium hysterophorus L. is among one of the most problematic invasive grassland weeds in Australia, and in many other countries around the world. It can reduce pasture and livestock production, natural community biodiversity, and negatively affect human and animal health. Sowing of selected suppressive pasture plants in parthenium weed infested grasslands has shown potential to improve efficacy of management. However, such species need to be tested for their ability to suppress weed growth under grazing conditions. The parthenium weed suppressive and fodder production capacity of six selected pasture species [purple pigeon grass (Setaria incrassata), buffel grass (Cenchrus ciliaris), butterfly pea (Clitoria ternatea), Kangaroo grass (Themeda triandra), bull Mitchell grass (Astrebla squarrosa) and Indian bluegrass (Bothriochloa pertusa)] was tested under no (0%), low (25%), moderate (50%) and heavy (75%) simulated grazing pressures in a grassland area of south-central Queensland, Australia. Purple pigeon grass, buffel grass and butterfly pea legume suppressed the growth of parthenium weed by >50% under low and moderate simulated grazing pressures, as well as generating moderate to high amounts of fodder biomass (up to 5.07 t ha-1 per year). Native species, Kangaroo grass and bull Mitchell grass both suppressed the parthenium weed's growth by >50% under low simulated grazing pressure, however, they generated low to moderate amounts of biomass, 1.83 t ha-1 and 2.7 t ha-1 per year, respectively. The sowing of selected suppressive pasture species in parthenium weed infested grasslands with low-to-moderate grazing pressure, assuming this corresponds closely with the simulated treatment, would provide an additional tool to the best practice weed management strategy as well as sustaining fodder production.
Article
Parthenium weed (Parthenium hysterophorus L.; Asteraceae) is an invasive weed species in agro-ecosystems. It causes huge losses to native biodiversity and agricultural productivity. This study was conducted to assess the combined effect of a leaf-feeding beetle, (Zygogramma bicolorata Pallister; Chrysomelidae) and suppressive plant species, bull Mitchell grass (Astrebella squrossa C.E. Hubb.; Poaceae) or butterfly pea (Clitoria ternatea L.; Fabaceae) on parthenium weed under shade house conditions. The suppressive plant species significantly reduced the parthenium weed height (16%), biomass (29%) and seed production (42%), in the absence of Z. bicolorata. However, this suppressive ability was further enhanced in the presence of Z. bicolorata. The combined effect of the suppressive plant species and Z. bicolorata further reduced the parthenium weed height (46%), biomass (66%) and seed production (95%). The combination also had a significant negative effect upon seed fill, decreasing the reproductive output of the current generation. The presence of Z. bicolorata also had positive effect on the biomass (10%) and plant height (11%) of both suppressive species. So, the combined use of suppressive plant species and the biological control agent suppressed parthenium weed more effectively than their sole use. Such integrated approaches should be prioritized for future management of parthenium weed.
Article
A study examining the composition and dynamics of the soil seedbank was conducted at two locations in central Queensland between December 2007 and May 2009. These two grassland communities were infested with parthenium weed (Parthenium hysterophorus L.), which had been present at both sites for at least 25 years. During the period of study, the seedbank varied between 5 962 and 16 206 seeds/m² at the Clermont site and between 6 795 and 24 862 seeds/m² at the Moolayember Creek site. Parthenium weed exhibited a very abundant and persistent seedbank, accounting for 80 − 87% of the seedbank at the Clermont site and 3 − 26% of the seedbank at the Moolayember Creek site. The species richness and species diversity of the seedbank, as well as the seed abundance of several native and introduced species, were higher at the Moolayember Creek site than at the Clermont site. The domination of the seedbanks by parthenium weed, especially at Clermont, suggests that the weed is having a substantial negative impact on seedbanks of native plant communities. The diversity of the seedbank at the Clermont site was found to be lower in comparison with that observed during an earlier study in 1995 − 1996, while the diversity at Moolayember Creek was found to have increased. Hence, the prolonged presence of parthenium weed may have substantially reduced the diversity of the seedbank at the Clermont site, while improved management practices may have increased diversity at the Moolayember Creek site.
Article
Substitutive (replacement) and partial additive experimental designs, with their underlying models, remain the two most popular techniques in weed-crop competition studies, despite considerable criticism of these approaches in the recent literature. We review standard designs for two-species competition experiments and demonstrate the advantages of a reciprocal yield model applied to data from an additive series experiment, using mixtures of Japanese millet and tomato. A traditional replacement series analysis failed to provide a general model of competition among these two species over several total plant densities, while an application of a reciprocal yield (inverse linear) model to the same data was successful. This technique allows evaluation of the influences of both weed on crop and crop on weed, as well as the partitioning of net competition effects into intra- and interspecific components. One Japanese millet plant was competitively equivalent to 3.7 tomato plants, as measured by effects on tomato biomass, while one tomato plant was equivalent to 0.14 Japanese millet plants, as measured by effects on millet biomass. Skewness of per plant biomass distribution is shown to be a result but not an unambiguous measure of competition. Expansion of a reciprocal yield model to mixtures of more than two species is illustrated using three species of duckweed. While some caution is recommended, the reciprocal yield analysis applied to data from appropriately designed experiments is a substantial improvement over more traditional methods.
Article
Woodland Pteridium aquilinum emerges earlier, but unshaded bracken grows more rapidly, so that by mid-season both have attained a similar stage of development. Nevertheless, abundances of some herbivore species were correlated with date of emergence, regardless of habitat. The effects of shade were examined by removing woodland trees and artificially shading open areas. Again some species responded by changing their distributions according to their known preferences for light or shade. Feeding preferences, growth and mortality rates of a sawfly caterpillar, Strongylogaster lineata, were studied on open bracken, where it is common, and on woodland bracken where it seldom occurs; type of habitat proved to have no effect on caterpillar performance. The degree of shading of the host plant thus has pronounced, but variable effects on the distribution of bracken herbivores. -from Authors
Article
Parthenium hysterophorus is an invasive weed in Australian rangelands. It displaces valuable fodder plants and causes significant production losses within the cattle industry. Glasshouse screening trials were used to test 20 selected fodder species (test species) for their suppressive ability against P. hysterophorus growth. The trials used two planting densities (four or six plants per pot) and five planting frequencies. Each density by planting frequency was replicated three times. The dry shoot biomass of the test species was used to calculate a suppression index, in order to rank the relative suppressive abilities of the test plants. Setaria incrassata, Panicum maxicum and Cenchrus ciliaris were ranked as strongly suppressive, while Astrebla squarrosa, Bothriochloa pertusa, Themeda triandra, Astrebla elymoides, Bothriochloa decipens, Eulalia aurea and Lablab purpureus were moderately suppressive. The other test species had only poor suppressive abilities. A second glasshouse trial assessed the growth characteristics of the test plants at 13, 27 or 40 days after transplantation (DAT). Test species that strongly suppressed the growth of Parthenium hysterophorus had several attributes that included the ability to attain a greater height, the rapid production of tillers or a branched canopy and an extensive leaf area and root system; these growth attributes were present as early as 13 DAT. The present glasshouse screening approach identified several fodder species for further testing in field trials, and because the attributes that allow the test species to suppress Parthenium hysterophorus are present at the earliest stages of the plant’s life cycle, a rapid screening method is proposed that assesses these attributes at 27 DAT.
Article
1. Invasive alien plants have serious economic and ecological impacts, for example, by displacing native plants and invertebrates, and their management is often costly and ineffective in the long term. Classical biological control using specialized, coevolved natural enemies from the native region of the invader is often advocated as a preferred alternative to chemical and mechanical control, but there is a lack of quantitative assessment of control of the target species and subsequent establishment of native vegetation and invertebrates. 2. Meta-analyses were carried out combining the results of 61 published studies (2000—2011) that quantified the impact of classical biocontrol at the level of individual target plants, target populations or non-target vegetation. Factors associated with the control programmes (invasive region, native region, plant growth form, target longevity, control agent guild, taxonomy and study duration) were analysed to identify patterns in control success. 3. On average, biocontrol agents significantly reduced plant size (28 ± 4%), plant mass (37 ± 4%), flower and seed production (35 ± 13% and 42 ± 9%, respectively) and target plant density (56 ± 7%). Beetles in the Chrysomelidae and Curculionidae families were more effective at reducing plant size than other groups. 4. Non-target plant diversity significantly increased by 88 ± 31% at sites where biocontrol agents were released, but it was largely unclear whether the replacement plant species were native or invasive. 5. Synthesis and applications. The number of studies that provide quantitative indications of the effectiveness of biocontrol and the response of non-target taxa has increased over the past decade, but remains small compared to the total number of publications on the classical biocontrol of invasive plants. Nonetheless, this study demonstrates the positive impacts of classical biocontrol and the re-establishment of native plants in a broad range of systems and establishes the value of classical biocontrol for the control of invasive alien plants. The Chrysomelidae and Curculionidae families were the most effective agents and we recommend these be prioritized in cases where potential agents of different taxa have also been identified. In addition, data on the recovery of native plant species and the invertebrate community remain sparse and it is recommended that future studies report the identity of plant species that replace target species as well as invertebrate community responses.
Article
Parthenium weed (Parthenium hysterophorus L.) is one of the most aggressive invasive weeds, threatening the natural and agro-ecosystems in over 30 countries worldwide. Parthenium weed inflicts losses to crops and pastures, degrading the biodiversity of natural plant communities, causing human and animal health hazards and seriously inflicting economic losses to people and their interests in many countries around the globe. Several of its biological and ecological attributes contribute towards its invasiveness. Various management approaches (viz. cultural, mechanical, chemical and biological control) have been used to minimize losses caused by this weed but most of these approaches are ineffective, uneconomical and/or have limitations. Although, chemical control using herbicides and biological control utilizing exotic insects and pathogens has been found to contribute to the management of the weed, nevertheless the weed remains a significant problem. An integrated management approach has been proposed here for the effective management of parthenium weed on a sustainable basis.
Article
Invading exotics typically face new competitors and an absence of specialized herbivores in their new ranges. Biological control attempts to reunite invasive weeds with coevolved herbivores and restoration can reduce the return of invaders by maximizing competition from native species. The integration of both approaches is seldom examined in detail, although the two should complement each other. We investigated the potential to suppress an important invasive plant, Canada thistle (Cirsium arvense [L.] Scop.), by integrating biological control and competition from two native grasses frequently used in rangeland restoration. We evaluated the impacts of Ceutorhynchus litura F. (Coleoptera: Curculionidae), a weevil used for Canada thistle biological control, alone and in combination with either needle and thread grass (Hesperostipa comata [Trin. & Rupr.] Barkworth) or alkali sacaton (Sporobolus airoides [Torr.] Torr.) in greenhouse competitive plantings. Weevil herbivory reduced root, but not shoot, biomass of Canada thistle. Competition from H. comata did not reduce biomass of thistles, but combinations of the weevil and H. comata greatly reduced thistle root biomass. S. airoides suppressed Canada thistle root biomass independent of weevils. Weevils had a positive indirect effect on the cool-season grass H. comata, presumably by reducing the competitive ability of thistles, but had no effect on biomass of the warm-season grass, S. airoides. Benefits of weevil presence as in augmentation of grass competition appear to depend on appropriate timing, and weevils provided the most benefit to the cool-season competitor. Our results suggest that restoration efforts can be complemented with insect biocontrol agents, although the timing of impact will depend on the particular weed species, grass competitors, and biocontrol insect agents involved.
Article
. 1We measured solar radiation reaching ten Quercus emoryi Torr. trees and recorded densities of four leaf-mining insect species on these trees from June until September 1982.2The measurements showed that densities of two leaf miner species were negatively correlated with solar radiation.3In a field experiment, polypropylene shade fabric was suspended 1.3 m above four experimental trees to test for effects of reduced sunlight.4Leaves of experimentally-shaded trees were heavier and contained lower percentages of proteins and gallotannins than leaves of control, sun trees, while per cent foliar monomeric, polymeric, and total phenols, and water content did not differ between sun and shaded trees.5Two of four leaf miner species had greater densities on experimentally-shaded trees than sun trees. One of these two species experienced lower survivorship on sun trees owing to high levels of death from unknown causes on sun trees.6Two leaf miner species had greater densities on sun trees. One of these species had higher survivorship on shaded trees owing to high levels of parasitism on sun trees.7We conclude that even subtle differences in shading influences leaf miner density and mortality; however, the effects of shading vary from positive to negative among leaf miner species.
Article
The germinable soil seedbank was determined at two sites in central Queensland on four separate occasions between February 1995 and October 1996. These sites were infested with parthenium weed (Parthenium hysterophorus L.), a serious invasive exotic weed. During this period, the seedbank varied between 3282 and 5094 seeds m−2 at the Clermont site, and between 20 599 and 44 639 seeds m−2 at the Moolayember Creek site. Parthenium hysterophorus exhibited a very abundant and persistent seedbank, accounting for 47–73% of the seedbank at Clermont and 65–87% of the seedbank at Moolayember Creek. The species richness and species diversity of the seedbank, and the seed abundance of many species, was lower at Moolayember Creek during spring (the time of year when the most dense infestations of the weed originate). Parthenium hysterophorus seedlings also emerged more rapidly from the soil samples than did those of all other species. Hence, it seems that various aspects of the weed's seed ecology, including abundance and the persistence of its seedbank and the rapid emergence of its seedlings, are major factors contributing to its aggressiveness in semiarid rangeland communities in central Queensland. The domination by P. hysterophorus of the seedbanks of these sites suggests that the weed is having a substantial negative impact on the ecology of these plant communities. The diversity of these seedbanks was found to be lower in comparison with that observed in other grassland communities that were not dominated by an invasive weed species. Hence, the prolonged presence of P. hysterophorus may have substantially reduced the diversity of these seedbanks, thereby reducing the ability of some of the native species to regenerate in the future.
Article
The interaction between grazing by Gastrophysa viridula and interspecific plant competition was investigated for Rumex obtusifolius growing in the field. During an eight-month growing season non-competing R. obtusifolius grew larger than competing plants although herbivore loads (beetle productivity per unit leaf area) were similar for competing and non-competing plants. However, grazing significantly reduced the growth of R. obtusifolius only in competing plants thus demonstrating a synergism between plant competition and invertebrate herbivory. The relevance of these findings for the distribution of plant species is discussed.
Article
The efficacy ofEpiblema strenuanaWalk., a stem-galling moth, as a biological control agent forParthenium hysterophorusL. (ragweed parthenium) was examined in a glasshouse pot experiment. The importance of the timing of insect attack and the presence of competition fromCenchrus ciliarisL. (buffelgrass) to the level of control obtained was tested. This was achieved by applyingE. strenuanaeggs at two stages of the weed's development: prior to stem elongation (35 days after emergence) and after stem elongation (53 days after emergence), in the presence or absence of moderate competition fromC. ciliarisseedlings. Application of a moderate number ofE.strenuanalarvae, at 53 days, reduced the number of immature capitula (36%), mature capitula (41%), and viable seeds (39%) produced byP. hysterophorusplants. Timing of the application ofE. strenuanawas important, with earlier application (at 35 days) causing a significant reduction in plant height (34%) and a more significant reduction in the number of mature capitula (74%) and viable seed (74%) produced. Competition fromC. ciliarishad a significant, and usually greater, effect on all of these characters, as well as significantly reducing the aboveground biomass of the weed. Plant height was the only measured character which was less affected by competition fromC. ciliaristhan byE. strenuanaattack. Reduction in weed seed production was greatest whenE. strenuanawas applied prior to stem elongation and when the weed was also experiencing competition fromC. ciliaris. In fact, a synergistic interaction was detected between plant competition and insect attack, and seed production was reduced by more than expected when these factors were combined. With both factors simultaneously present, seed production was reduced to 2% of that of the control plants.E. strenuanaattack did not affect the quality ofP. hysterophorusseeds produced. These levels of control do not often occur in the field and a number of possible explanations for this are discussed.
Article
Relative growth rate and relative nitrogen accumulation rate for fifth-instar Spodoptera eridania larvae vary less than 20% on artificial diets in which protein content varies more than 250%, due to compensatory adjustments in consumption rate and changes in efficiencies of food and nitrogen utilization. The substitution of zein for two-thirds of the casein in a diet containing 26.0% protein results in a 25% decrease in both relative growth and nitrogen accumulation rates, due to reduced values of relative consumption rate, relative nitrogen consumption rate, approximate digestibility, approximate digestibility of nitrogen and efficiency of conversion of digested nitrogen. Although larval growth rate is relatively independent of diet nitrogen, larval composition is highly dependent upon both nitrogen quantity and quality. As diet nitrogen increases, larval nitrogen content increases and fat content decreases. Larvae on diets containing a mixture of casein and zein produce 3.5–3.9 times as much uric acid and respire at rates significantly higher than larvae on diets containing the same total amount of protein but lacking zein. Thus, there is a measurable metabolic cost associated with processing low quality protein. We conclude, however, that elevated metabolic rates of larvae on diets containing nutritionally unbalanced protein are not the cause of reduced growth rates. On these diets, growth is limited byan amino acid present in limiting quantities, and the elevated metabolic rate is due, at least in part, to increased synthesis of uric acid. Finally, we discuss the possibility that variation in amino acid profiles across host plant species might be a factor favouring specialization in insect herbivores.
Parthenium weed (Parthenium hysterophorus L.) research in Australia: new management possibilities, 26-30
  • S W Adkins
  • C O'donnell
  • N Khan
  • T L Nguyen
  • A Shabbir
  • K Dhileepan
Adkins, S.W., O'Donnell, C., Khan, N., Nguyen, T.L., Shabbir, A., Dhileepan, K., 2010. Parthenium weed (Parthenium hysterophorus L.) research in Australia: new management possibilities, 26-30 September 2011. In: Zydenbos, S.M. (Ed.), The 17th Australasian Weeds Conference. New Zealand Plant Protection, pp. 120-123 (Christchurch, New Zealand).
  • K Dhileepan
  • R Mcfadyen
  • L Strathie
  • K Khan
Dhileepan, K., McFadyen, R., Strathie, L., Khan, K., 2019. Biological control. In: Adkins, S., Shabbir, A., Dhileepan, K. (Eds.), Parthenium Weed: Biology, Ecology and Management. CABI, UK, pp. 131-156.
The Reproductive Capacity of Parthenium Weed (Parthenium Hysterophorus L.) under Different Climatic Conditions
  • T L T Nguyen
  • S C Navie
  • S W Adkins
Nguyen, T.L.T., Navie, S.C., Adkins, S.W., 2010. The Reproductive Capacity of Parthenium Weed (Parthenium Hysterophorus L.) under Different Climatic Conditions. Christchurch, New Zealand, pp. 124-127.
The interaction between natural enemies and interspecific plant competition in the control of invasive pasture weeds
  • A W Sheppard
Sheppard, A.W., 1996. The interaction between natural enemies and interspecific plant competition in the control of invasive pasture weeds, 19-26 January 1996.. In: Moran, V.C., Hoffmann, J.H. (Eds.), Proceedings of the 9th International Symposium on Biological Control of Weeds, Stellenbosch, South Africa, pp. 47-53.