Classical biological control, i.e. the introduction and release of exotic insects, mites, or pathogens to give permanent control, is the predominant method in weed biocontrol. Inundative releases of predators and integrated pest management are less widely used. The United States, Australia, South Africa, Canada, and New Zealand use biocontrol the most. Weeds in natural ecosystems are increasingly becoming targets for biocontrol. Discussion continues on agent selection, but host-specificity testing is well developed and reliable. Post-release evaluation of impact is increasing, both on the target weed and on non-target plants. Control of aquatic weeds has been a notable success. Alien plant problems are increasing worldwide, and biocontrol offers the only safe, economic, and environmentally sustainable solution.

/pdf/biological-control-of-weeds-322a9vo10y.pdf

Biological control of weeds

What determines which plant species are susceptible to a given plant pathogen is poorly understood. Experimental inoculations with fungal pathogens of plant leaves in a tropical rain forest show that most fungal pathogens are polyphagous but that most plant species in a local community are resistant to any given pathogen. The likelihood that a pathogen can infect two plant species decreases continuously with phylogenetic distance between the plants, even to ancient evolutionary distances. This phylogenetic signal in host range allows us to predict the likely host range of plant pathogens in a local community, providing an important tool for plant ecology, design of agronomic systems, quarantine regulations in international trade, and risk analysis of biological control agents. In particular, the results suggest that the rate of spread and ecological impacts of a disease through a natural plant community will depend strongly on the phylogenetic structure of the community itself and that current regulatory approaches strongly underestimate the local risks of global movement of plant pathogens or their hosts.

/pdf/phylogenetic-signal-in-plant-pathogen-host-range-2mcrl227js.pdf

Phylogenetic signal in plant pathogen–host range

More than 5000 introductions of about 2000 species of exotic arthropod agents for control of arthropod pests in 196 countries or islands during the past 120 years rarely have resulted in negative environmental effects. Yet, risks of environmental effects caused by releases of exotics are of growing concern. Twenty countries have implemented regulations for release of biological control agents. Soon, the International Standard for Phytosanitary Measures (ISPM3) will become the standard for all biological control introductions worldwide, but this standard does not provide methods by which to assess environmental risks. This review summarizes documented nontarget effects and discusses the development and application of comprehensive and quick-scan environmental risk assessment methods.

https://www.fcnym.unlp.edu.ar/catedras/controlbiologico/Bibliografia%20PDF/600LentRisksAssessExoticsAnnuRev2006.pdf

Assessing risks of releasing exotic biological control agents of arthropod pests

Foreword J. Waage. Preface. A History of Methodological, Theoretical and Empirical Approaches to Biological Control G.M. Gurr, et al. Classical Arthropod Biological Control: Measuring Success, Step By Step R.G. van Driesche, M.S. Hoddle. Success in Biological Control of Arthropods by Augmentation of Natural Enemies J.C. van Lenteren. Success in Conservation Biological Control of Arthropods G.M. Gurr, et al. Success in Biological Control of Terrestrial Molluscs G.R. Port, et al. Success in Biological Control of Aquatic Weeds by Arthropods I.W. Forno, M.H. Julien. Success in Biological Control of Terrestrial Weeds by Arthropods P. Syrett, et al. Success in Biological Control of Plant Pathogens and Nematodes by Microorganisms J.M. Whipps, K.G. Davies. Success in Biological Control of Soil-dwelling Insects by Pathogens and Nematodes T.A. Jackson, et al. Success in Biological Control of Above-ground Insects by Pathogens W.D. Gelernter, C.J. Lomer. Success in Biological Control of Weeds by Pathogens, Including Bioherbicides B.A. Auld. Success in Biological Control of Vertebrate Pests G.J. Hickling. Non-target Effects of Biological Control Agents F.G. Howarth. Synthesis: The Future Success of Biological Control S.D. Wratten, G.M. Gurr. Index.

Biological control : measures of success

In the past 100 years many exotic naturalenemies have been imported, mass reared andreleased as biological control agents. Negativeenvironmental effects of these releases haverarely been reported. The current popularity ofinundative biological control may, however,result in problems, as an increasing number ofactivities will be executed by persons nottrained in identification, evaluation andrelease of biological control agents.Therefore, a methodology for risk assessmenthas been developed within the EU-financedproject `Evaluating Environmental Risks ofBiological Control Introductions into Europe[ERBIC]' as a basis for regulation of importand release of exotic natural enemies used ininundative forms of biological control (i.e.not in `classical biological control' thoughsome of the same principles and approachesapply). This paper proposes a general frameworkof a risk assessment methodology for biologicalcontrol agents, integrating information on thepotential of an agent to establish, itsabilities to disperse, its host range, and itsdirect and indirect effects on non-targets. Ofthese parameters, estimating indirect effectson non-targets will be most difficult, asmyriads of indirect effects may occur whengeneralist natural enemies are introduced. Theparameter `host range' forms a central elementin the whole risk evaluation process, becauselack of host specificity might lead tounacceptable risk if the agent establishes anddisperses widely, whereas, in contrast, amonophagous biological control agent is notexpected to create serious risk even when itestablishes and disperses well. Drawing onpublished information and expert opinion, theproposed risk assessment methodology is appliedto a number of biological control agentscurrently in use. These illustrative casehistories indicate that the risk assessmentmethodology can discriminate between agents,with some species attaining low `risk indices'and others scoring moderate or high. Riskindices should, however, not be seen asabsolute values, but as indicators to which ajudgement can be connected by biologicalcontrol experts for granting permission torelease or not.

/pdf/environmental-risk-assessment-of-exotic-natural-enemies-used-1gybt6nmbr.pdf

Environmental risk assessment of exotic natural enemies used in inundative biological control

SUMMARY

A strategy for establishing the specificity and safety of an organism as a biological weed control agent is described. A critical first step is to expose to its attack a small group of plants very closely related and exhibiting morphological and biochemical similarities to the weed. To prevent an erroneous negative result tests are also made on selected cultivated plants, including those closely related to the weed, those of which the associated insects and fungi are little known, those that have evolved apart from or been little exposed to the agent, those attacked by closely related organisms and those already recorded as hosts.



The circumstances under which the strategy might fail to indicate safety are discussed, i.e. polyphagous organisms attacking plants irregularly distributed throughout many families, organisms highly specific to two alternate hosts, and those attacking two or three phylogenetically widely separated plant groups. The additional crop plant testing, included in the overall strategy to deal with such possible failures, is discussed.



It is shown that the strategy would have included Sesamum tndicum in the list of plants challenged by the bug Teleonemia scrupulosa in biological testing for control of Lantana camara, thereby forewarning of the attack that was subsequently observed in Africa.

A strategy for evaluating the safety of organisms for biological weed control

Summary

Many insect agents, selected for the biological control of weeds and tested under restricted cage conditions, have been rejected as unsafe for introduction because of an apparent increase in host range compared with that observed under natural conditions. These aberrant results appear to be due to the insects' inability to follow the normal behavioural sequence based on appropriate cues which lead to correct host selection. It is suggested here that a reverse sequence of testing which progressively reduces the degree of restriction and deletes unattacked plants at each stage, until only a few remain to be tested under conditions as near natural as possible, would allow previously rejected insects to be used as biological control agents.

A testing sequence for reducing rejection of potential biological control agents for weeds

SUMMARY
During investigations on the parasites of Chondrillajuncea in the Mediterranean region, the rust, Puccinia chondrillina, was found to be one of the most damaging. This macrocyclic and autoecious rust which is specific to the genus Chondrilla, remains active throughout the year and attacks all stages and all parts of the plant. In the Mediterranean region the rust appears to multiply solely by the uredo-stages and the teleutospores produced at the end of the summer have no obvious role in the life-cycle of the fungus. The uredospores germinated at temperatures of 0–36 °C and were used for inoculation of Chondrilla seedlings in the greenhouse.

The rust occurs from the cold continental climates of southern Siberia to the hot, Mediterranean ones of Portugal and North Africa. In many situations the rust has been found to play an important role in the reduction of C. juncea populations. Young seedlings were highly susceptible to attack and were often destroyed. Older rusted plants gave many fewer viable seeds than healthy plants and were also often unable to produce new rosettes from their roots.

The biology of Puccinia chondrillina a potential biological control agent of skeleton weed

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A strategy for evaluating the safety of organisms for biological weed control

A testing sequence for reducing rejection of potential biological control agents for weeds

The biology of Puccinia chondrillina a potential biological control agent of skeleton weed