Opportunities for biological weed control in Europe

The development and application of biological weed control offer greatopportunities not only for farmers, nature conservationists and othervegetation managers but also for institutions and companies that wish tosell plant protection services and products, and for the general publicthat demands safe food and a visually attractive and diverseenvironment. Despite the obvious opportunities for biological weedcontrol, few control agents are actually being used in Europe. Potentialagent organisms have features that make them particularly strong anduseful for biological control, but they also have weaknesses. Weaknessesinclude a too narrow or too wide host specificity, lack of virulence, orsensitivity to unfavourable environmental conditions.Developing specific knowledge on the interaction between weeds andpotential biological control agents, as well as expertise to increasethe effect of control agents and so achieve sufficient weed control in acost-effective manner, should have the highest priority in researchprogrammes. From 1994 to 2000 most ongoing research on biological weedcontrol in Europe was combined in a cooperative programme. This COSTAction concentrated on the interactions between five target crop weedsand their antagonists (pathogens and insects), on furthercharacterisation of the specific blems and potential control agents andon the most suitable biological control approach.The next major challenge will be to apply the findings provided byCOST-816 to the development of practical control solutions. The leadingobjective of a new concerted research programme with European dimensionswill be to stabilise or even promote biodiversity in the most importantEuropean ecosystems by integrating biological weed control in themanagement of these systems.     

Prioritisation of potential agents for the biological control of the invasive alien weed,Pereskia aculeata (Cactaceae), in South Africa

Pereskia aculeata Miller (Cactaceae) is an invasive alien species in South Africa that is native in Central and South America. In South Africa, P. aculeata outcompetes native plant species leading to a reduction in biodiversity at infested sites. Herbicidal and mechanical control of the plant is ineffective and unsustainable, so biological control is considered the only potential solution. Climatic matching and genotype matching indicated that the most appropriate regions in which to collect biological control agents were Santa Catarina and Rio de Janeiro provinces in Southern Brazil. Surveys throughout the native distribution resulted in 15 natural enemy species that were associated with the plant. Field host range data, as well as previous host plant records, were used to prioritise which of the species were most likely to be suitably host specific for release in South Africa. The mode of damage was used to determine which species were most likely to be damaging and effective if released. The most promising species prioritised for further study, including host specificity and impact studies, were the stem-wilter Catorhintha schaffneri Brailovsky & Garcia (Coreidae); the stem boring species Acanthodoxus machacalis Martins & Monné (Cerambycidae), Cryptorhynchus sp. (Curculionidae) and Maracayia chlorisalis (Walker) (Crambidae) and the fruit galler Asphondylia sp. (Cecidomyiidae). By prioritising the potential biological control agents that are most likely to be host-specific and damaging, the risk of conducting host specificity testing on unsuitable or ineffective biological control agents is reduced.     

Current understanding of the development of sex attractant-based biocontrol in burnet moths

Burnet moths, also known as the family Zygaenidae, are a typical diurnal family of Lepidoptera. Some species are important insect pests in agriculture and forestry. The use of sex attractants is one of the most important measures in the integrated pest management of burnet moths because these attractants are highly efficient, do not cause pollution, and are convenient and harmless to natural enemies. The earliest information about sex pheromones in Zygaenidae was reported in 1972. To date, many studies have described sex pheromones and attractants of species in Zygaenidae. Here, we review a total of 22 sex attractant compositions identified for 57 species of Zygaenidae and compare the differences in the structures of sex attractants among these species. The application of sex attractants in seasonal monitoring showed that the main activity period of zygaenid moths is from May to September each year. However, there are few reports on the effects of sex attractants on mass trapping of members of the family Zygaenidae. The ratio and degradation of sex attractants and the trap color, shape and hanging height were considered the main factors influencing capture effectiveness. Directions for further study of burnet moths are also discussed.     

The value of simulating herbivory in selecting effective weed biological control agents

Invasive species have a significant economic and ecological cost and biological control can be a powerful tool in their management. Classical biological control practice involves the re-establishment of trophic links between specialist insect and fungal agents to regulate populations of invasive species. However, the permanent nature of biological control agent introductions raises concerns about the unintended consequences of such introductions on non-target organisms, particularly when such agents are ineffective on their target organisms. In this paper, we explore the current debate in the selection of agents for weed classical biological control. We then propose an alternate approach, based on studying plant response to simulated herbivory, that could minimize the chances of release of ineffective agents. Simulating herbivory could yield insights into the vulnerability of plants to certain types of damage. Selection of agents within guilds that are likely to have a significant influence on the plant can improve the chances of achieving biological control sooner and reduce the likelihood of releasing ineffective agents that may have non-target impacts. We propose a method by which simulated herbivory could be integrated into the agent selection process and discuss its strengths and shortcomings. We present case studies of two Neotropical weeds illustrating how this method could be applied.     

The use of herbicides for weed control in flooded rice in North Italy

The use of chemicals to control weeds in flooded rice in the Po Valley, Italy is restricted by limited knowledge of potentially useful herbicides. Different strategies of chemical weed control, including different application timings of several types of herbicides are compared based on effectiveness and selectivity. Echinochloa spp., the most common weed was, in the experimental conditions, better controlled with early applications (pre-sowing and preemergence) of new herbicides which were effective substitutes for molinate, the use of which is no longer allowed in some Italian areas. Alisma plantago-aquatica, Bolboschoenus maritimus and Schoenoplectus macronatus were controlled by different types of herbicides applied post-emergence. Cinosulfuron (sulfonylurea) showed the highest effectiveness and selectivity in controlling the more common Hetherantera spp., even when applied in very low amounts.     

Prioritising potential guilds of specialist herbivores as biological control agents for prickly acacia through simulated herbivory

Understanding plant response to herbivory facilitates the prioritisation of guilds of specialist herbivores as biological control agents based on their potential impacts. Prickly acacia ( Acacia nilotica ssp. indica ) is a weed of national significance in Australia and is a target for biological control. Information on the susceptibility of prickly acacia to herbivory is limited, and there is no information available on the plant organ (i.e. leaf, shoot and root in isolation or in combination) most susceptible to herbivory. We evaluated the ability of prickly acacia seedlings, to respond to different types of simulated herbivory (defoliation, shoot damage, root damage and combinations), at varying frequencies (no herbivory, single, two and three events of herbivory) to identify the type and frequency of herbivory that will be required to reduce the growth and vigour. Defoliation and shoot damage, individually, had a significant negative impact on prickly acacia seedlings. For the defoliation to be effective, more than two defoliation events were required, whereas a single bout of shoot damage was enough to cause a significant reduction in plant vigour. A combination of defoliation + shoot damage had the greatest negative impact. The study highlights the need to prioritise specialist leaf and shoot herbivores as potential biological control agents for prickly acacia.     

Host range of the defoliator Strepsicrates sp. is too broad for biological control of the invasive weed Rhodomyrtus tomentosa

In its native range the invasive weed, Rhodomyrtus tomentosa is host to a suite of herbivores. One, Strepsicrates sp. (Lepidoptera: Tortricidae), was collected in China in 2014, introduced under quarantine in Florida, USA, and tested against related species to determine its host range and suitability for biological control. In no-choice tests, neonates fed and completed development to the pupal stage on several species of Myrtaceae, including the target weed R. tomentosa, the exotics Melaleuca quinquenervia, and Eucalyptus camaldulensis, and three native species, Eugenia axillaris, Mosiera longipes and Morella cerifera (Myricaceae). Due to the broad host range exhibited in quarantine testing, this species will not be pursued as a biological control agent of R. tomentosa.     

Phytophagous insects found onSalsola in Turkey during exploration for biological weed control agents for California

A total of 50 species of phytophagous insects were collected from Russian thistle (Salsola iberica Sennen & Pau),S. kali L.,S. tragus L., and their apparent hybrids in Turkey during June and July, 1970. These collections contained many new host-plant and locality records forSalsola insects. Among the natural enemies detected and thought to warrant further consideration as agents worth importing for the biological control of Russian thistle in California were:Piesma salsolae (Becker) (Hemiptera-Heteroptera: Piesmatidae); Coleophora klimenoschiella Toll (Lepidoptera: Coleophoridae); an unidentified species ofPhycitidae (Lepidoptera), and an undeterminedLixus sp. (Coleoptera: Curculionidae). Coleophora parthenica Meyrick, scheduled for initial release in California for the biological control of Russian thistle in early-1973, also is reported for the first time from Turkey.     

对性引诱剂监测桔小实蝇雄成虫技术的改进

研究了添加方式、监测点位置以及监测区域环境对应用性引诱剂甲基丁香酚监测桔小实蝇Bactrocera dorsalisHendel雄成虫动态效果的影响。试验结果表明,采用分期分批、多次添加性引诱剂的方式监测桔小实蝇雄成虫动态,可消除因监测区域内所有诱瓶同一时间添加性引诱剂而造成的浓度突变所引起的成虫出现干扰性高峰,获得更准确的虫情监测结果;监测点的设置位置明显影响监测结果,监测点应包括果园内和果园外;选择较大且环境复杂的区域作为监测点可获得更明确的年发生动态规律。在以上研究基础上,提出了应用性引诱剂监测桔小实蝇雄成虫动态的监测方法。     

Molecular biology of weed control

The vast commercial effort to utilize chemical and molecular tools to solve weed control problems has had a major impact on the basic biological sciences as well as benefits to agriculture, and the first generation of transgenic products has been successful, while somewhat crude. More sophisticated products are envisaged and expected. Biotechnologically-derived herbicide-resistant crops have been a considerable benefit, yet in some cases there is a risk that the same useful transgenes may introgress into related weeds, specifically the weeds that are hardest to control without such transgenic crops. Biotechnology can also be used to mitigate the risks. Molecular tools should be considered for weed control without the use of, or with less chemicals, whether by enhancing crop competitiveness with weeds for light, nutrients and water, or via allelochemicals. Biocontrol agents may become more effective as well as more safe when rendered hypervirulent yet non-spreading by biotechnology. There might be ways to disperse deleterious transposons throughout weed populations, obviating the need to modify the crops. This revised version was published online in August 2006 with corrections to the Cover Date.     

Insect herbivores associated with the introduced weed Bidens frondosa L. (Asteraceae) in Korea,and their potential role as augmentative biological control agents

The annual herb Bidens frondosa L., native to North America, is an invasive weed. Currently no information is available on the insect herbivores associated with this weed in Korea. A survey was carried out at two‐weekly intervals from May to October 2008 at two sites, and the incidence and abundance of various insect herbivores studied. A total nine species of insects was recorded and among them the defoliating caterpillar Hadjina chinensis (Wallengren) (Lepidoptera) was the only species known to have host plants restricted to genus Bidens. Further host specificity studies are required to evaluate the potential of this insect as a candidate for augmentative biological control agent for B. frondosa in Korea. All other insect species are either polyphagous or known crop pests.     

杂草生防作用物对本土生物群落的影响

传统生物防治是治理外来入侵杂草危害切实可行的有效策略和途径,近来对传统生物防治的批评主要集注于,引进的生防作用物攻击威胁本土非靶标生物。引进的生防作用物可能对本土非靶标生物产生直接和间接影响,这类影响通过不同营养级生物之间的取食关系,以及通过同一营养级内生物间的竞争关系,而影响本土非靶标生物群落。列举若干杂草生物防治案例对以上影响方式及其发生途径进行了评述。就防范杂草生防作用物对非靶标生物的负面影响,提出了以下对策:(i)把引进天敌防治外来入侵生物作为最后的有效手段;(ii)适当增加对非靶标生物潜在影响的生态学评估;(iii)选择寄主专一性强而且能有效控制靶标杂草的天敌;(iv)加强对杂草传统生物防治的生态学研究。     

Selection of pathogen agents in weed biological control: critical issues and peculiarities in relation to arthropod agents

Abstract  Plant pathogens are playing an increasing role in classical biological control of weeds worldwide. This paper presents an explicit framework consisting of various interconnected steps to facilitate and streamline the selection process for pathogen agents. It also highlights and discusses critical issues associated with the various steps of the selection framework such as the climatic-matching approach to find well-adapted agents, host–pathogen matching and pathogen genetic structure. Processes and issues relating to the selection of pathogens are then contrasted with those usually adopted for arthropod selection in weed biological control. In both cases optimising the level of genetic diversity in introduced agents is seen as beneficial to biological control success. The difference in regulatory approach for multiple and genetically pure pathogen strains vs. genetically variable arthropod agents is highlighted for further scientific debate.     

Interaction among two biological control agents and the developmental stage of their target weed,Dalmatian toadflax,Linaria dalmatica (l.) Mill. (Scrophulariaceae)

An experiment with potted Linaria dalmatica (L.) Mill. was set up to test the effects of root‐feeding by Eteobalea (syn. Stagmatophora) intermediella Riedl (Lep. Cosmopterigidae) and stem‐mining by Mecinus janthinus Germar (Col. Curculionidae), as well as the interaction among the insects and the developmental stage of the host plant. During the summer season, mining by M. janthinus decreased the stem biomass substantially, while E. intermediella did not produce statistically significant effects on the performance of host plant individuals (the experimental conditions represented the effect of the univoltine M. janthinus adequately, but the potentially important effect of mining by the second generation of E. intermediella, at the beginning of the growing season, was not assessed). M. janthinus survived almost exclusively on plants in the flowering stage, although adult females readily used vegetative (younger) plants for oviposition. E. intermediella had a higher chance of survival on vegetative plants. Both species have recently been released as biological control agents on L. dalmatica in North America. For this purpose the complementary survival rates on the two developmental stages of the host plant is advantageous.     

Biological control of weeds by means of plant pathogens: Significance for integrated weed management in modern agro-ecology

Biological control of weeds by using plant pathogens has gainedacceptance as a practical, safe, environmentally beneficial, weedmanagement method applicable to agro-ecosystems. The interest in thisweed control approach from public and private groups, and support forresearch and developmental effort, are on the upswing. This increasinginterest is stimulated largely due to major economic, social, andenvironmental forces that are directing our choices in crop productionpractices. Some of these changes are market-driven while others aresocial and ecological in nature. These changes are in turn influencingthe choices in weed control methods. In this regard, biocontrol withplant pathogens has been proven a feasible, albeit minor, component ofmodern integrated weed-management systems. This environmentallybeneficial method should be promoted and exploited further to meet thecurrent and future challenges in weed management in agro-ecosystems.     

Lek behaviour of Drosophila cnecopleura in Hawaii

ABSTRACT.

• 1 Male spacing, aggression, and female visitation are described for a lek of Drosophila cnecopleura Hardy within a Hawaiian rainforest. The lek was located at a single tree of Pisonia umbellifera, and the males present defended individual leaves as mating territories. Observations were made in October 1986 and April 1987.
• 2 Approximately twice as many males were present at the lek in October than in April. At both times, males generally perched on the lowest leaves in the lek. Individuals did not remain on particular leaves for long periods of time but frequently moved among different territories.
• 3 Males engaged in two types of aggressive encounters, face-offs and chases, and in all encounters the resident displaced the intruder.
• 4 Females were sighted at the lek 0.69 times/h in October and 0.23 times/h in April. Most of the leaves visited by females were among the lowest in the lek.

     

Risk analysis and management decisions for weed biological control agents: Ecological theory and modeling results

Biologically based control methods offer many advantages for the control of invasive plant species; however, these methods are not without risks to native species. Thus, there is a need for more effective and efficient methods of risk analysis for biological control agents. We show how the process of ecological risk assessment established by the United States’ Environmental Protection Agency may be adapted to improve assessment of the risks of proposed biological control agents. We discuss the risks posed by weed biological control agents, and present a simple individual-based model of herbivorous insect movement and oviposition on two species of host plant, a target invasive plant species and a non-target native species, in simulated landscapes. The model shows that risks of non-target impacts may be influenced by the details of the movement behavior of biological control agents in heterogeneous landscapes. The specific details of insect movement that appear to be relevant are readily measured in field trials and the general modeling approach is readily adapted to real landscapes. Current biological control risk assessments typically emphasize effects analysis at the expense of exposure analysis; the modeling approach presented here provides a simple and feasible way to incorporate exposure analyses. We conclude that models such as ours should be given serious consideration as part of a comprehensive strategy of risk assessment for proposed weed biological control agents.     

不同控草措施对高温季节华南地区蔬菜田杂草群落的影响

华南地区高温季节从6月持续到10月,田间杂草危害严重,当前高温季节田间杂草群落发生格局相关的研究资料积累不足。因此在广州高温季节于标准化菜田通过田间杂草调查、小区控草试验和室内土壤培养,研究了杂草群落发生规律和菜田不同清园和土壤处理控草措施对田间杂草群落短期防效和后续影响。结果表明,试验田休耕50 d后,田间杂草群落中禾草类杂草种类较少但发生量明显占优,阔叶类杂草种类较多而危害总体较轻,莎草类杂草种类较少,发生量与阔叶草相当;牛筋草(Eleusine indica)呈现明显的单优势,光头稗(Echinochloa colona)、千金子(Leptochloa chinensis)、碎米莎草(Cyperus iria)、草龙(Ludwigia hyssopifolia)等的盖度也较高。休耕后取田间土壤在不同温度条件下培养的结果亦表明,高温促进禾草类杂草的出苗和幼苗生长(尤其是40℃/35℃)而15℃恒温培养14 d几乎仅有阔叶类杂草出苗。不同控草措施处理的田间试验结果表明,百草枯处理(900 g a.i./hm~2)后阔叶类杂草总盖度上升的趋势被扭转为禾草类杂草持续占优势;喷施百草枯并铲草处理30 d后杂草盖度即恢复至60%以上,而配合喷施丁草胺(1350 ga.i./hm~2)、乙草胺(750 ga.i./hm~2)、精异丙甲草胺(750 ga.i./hm~2)或二甲戊灵(600 ga.i./hm~2)进行土壤处理30 d后可使杂草盖度与仅喷施百草枯处理分别下降72.9%、84.6%、83.9%和77.5%;土壤处理前配合浅翻耕可明显提升控草效果。典范对应分析(CCA)结果表明,控草处理70d后,百草枯、铲草和翻耕处理均对试验田间杂草群落结构具有显著影响(P0.01),田间各主要杂草在CCA排序图中明显分为两个类群:1)光头稗、牛筋草、千金子、马唐(Digitaria sanguinalis)、水虱草(Fimbristylis miliacea)和三头水蜈蚣(Kyllinga triceps);2)草龙、胜红蓟(Ageratum conyzoides)、鳢肠(Eclipta prostrata)、马齿苋(Portulaca oleracea)等阔叶类杂草和碎米莎草。     

Risk analysis and management decisions for weed biological control agents: Ecological theory and modeling results

Biologically based control methods offer many advantages for the control of invasive plant species; however, these methods are not without risks to native species. Thus, there is a need for more effective and efficient methods of risk analysis for biological control agents. We show how the process of ecological risk assessment established by the United States’ Environmental Protection Agency may be adapted to improve assessment of the risks of proposed biological control agents. We discuss the risks posed by weed biological control agents, and present a simple individual-based model of herbivorous insect movement and oviposition on two species of host plant, a target invasive plant species and a non-target native species, in simulated landscapes. The model shows that risks of non-target impacts may be influenced by the details of the movement behavior of biological control agents in heterogeneous landscapes. The specific details of insect movement that appear to be relevant are readily measured in field trials and the general modeling approach is readily adapted to real landscapes. Current biological control risk assessments typically emphasize effects analysis at the expense of exposure analysis; the modeling approach presented here provides a simple and feasible way to incorporate exposure analyses. We conclude that models such as ours should be given serious consideration as part of a comprehensive strategy of risk assessment for proposed weed biological control agents.