The control of vertebrate pests by vertebrate predators

Carnivores can control mammalian pests for long periods, but only after pest numbers have been reduced by other means. In Australia, the cause is prolonged dry weather. The consequent low populations of rabbits can then be regulated by European foxes, feral cats and dingoes. Kangaroos, and probably feral goats and pigs, succumb to dingoes at the same time, as substitute prey for rabbits. In the general case, such regulatory predation may be triggered climatically, by disease or by human intervention. When predators are themselves pests to be controlled, integrated pest management may be required to avoid unwanted resurgences of other pests.     

The need for biological assessment of water quality: Australian perspective

Abstract Biological assessment of water quality in Australia is entering a stage of rapid development largely because of the inclusion of biological indicators in water quality guidelines and growing concern for ecological values. Approaches to water quality assessment include toxicity testing, use of biomarkers and several methods using community structure. For assessment diverse organisms such as fish, algae and (the most commonly used) macro-invertebrates are used. Interaction of data analysis with methods of data collection requires co-ordinated research on both fronts. Recent developments in the use of multivariate statistics to produce models for predicting water quality are likely to be useful in Australia. Much innovative work is still needed in Australia on the use of algae and fish, defining tolerance categories and establishing monitoring programmes performed in time-frames equivalent to those in use for physical and chemical methods.     

Perspectives of non-phytoseiid predators for the biological control of plant pests

Non-phytoseiid mites of potential importance in the biocontrol of plant pests include a dozen families. The host plant constitutes the universe in which pests and predators interact; thus plant growth pattern, leaf structure and various available nutrients may affect the control potential of the mites. The role of infochemicals in prey finding by non-phytoseiids probably differs among the various families. Prey size may be important in control success when predaceous mites feed on insect pests. Interactions between phytoseiids and members of other families may hinder or complement pest control. Little is known of the effects of plant-protection chemicals on non-phytoseiid predators, but they appear to be quite variable. Current research onHemisarcoptes, a parasite of armored scale insects, is reviewed, including a successful introduction into New Zealand. Active mite slicing into host shields and deutonymph interactions with its vector-beetle are important aspects of the predator's effectiveness. Further research should include: collecting (with emphasis on the tropics and subtropics), describing and testing additional mite species against more pests; assaying pesticide effects; studying interactions between predators of different families, especially on uncultivated plants; and trying more predaceous mites against nematodes, plant diseases and weeds.     

载体植物在温室作物害虫生物防治中的应用

增补式生物防治是利用天敌昆虫或捕食螨防治害虫最常用的方法,释放的天敌昆虫或捕食螨能否成功建立稳定种群,是决定其持久高效控害的首要关键因素。然而在生产应用中,经常因释放的天敌昆虫或捕食螨不能成功定殖而无法达到理想的防治效果。载体植物系统是天敌饲养和释放的新方法,结合了增补式和保护式生物防治的优点,既能实现天敌昆虫或捕食螨的大量饲养,又能为释放的天敌昆虫或捕食螨提供替代食物和栖息场所,促进其建立稳定的种群,对实现天敌昆虫或捕食螨高效持久控害具有重要的意义。本文系统介绍了载体植物系统的构建、国内外研究现状,指出了现存的问题,并给出相应的建议。     

Alyssum flowers promote biological control of collard pests

Collard greens Brassica oleracea (L.) are often attacked by various pests including whiteflies, aphids and diamondback moth. Hitherto, the main method used to manage these pests in Brazil has been the application of a limited number of registered insecticides. The search for more sustainable pest management strategies is therefore warranted. In this context, the conservation biological control stands out as an appealing alternative. Conservation biological control is achieved, at least in part, by strip-cultivating and/or conserving flowering plants within the agroecosystem. The present study investigates how alyssum flowers Lobularia maritima (L.) could contribute to the attraction of natural enemies and to the management of collard pests. Two field experiments were conducted in different years. Each experiment consisted of two treatments and three replicates, which were set up in a completely randomized design. The treatments were (1) collards alone, and (2) collards + alyssum. We evaluated weekly the population density of natural enemies and pests on both treatments. The results show that the alyssum flowers attractiveness contributed to increase the abundance of generalist predators during both experiments, which in turn translated into a significant reduction of collards pests, especially aphids. Some of the main predators attracted/harbored by alyssum flowers were spiders, coccinellids, syrphids and Orius sp. Finally, strip intercropping alyssum with collards can be an important strategy to manage brassica pests and cope with the limited availability of insecticides registered for this vegetable crop.     

A knapweed biological control perspective

Diffuse and spotted knapweed (Centaurea diffusa Lam. and C. stoebe micranthos (Gugler) Hayek) are Eurasian plants that devastate dry and mesic North American grasslands. They have a mutualistic association with arbuscular mycorrhizal fungal (AMF) phylotypes with hyphal links to nearby plants and a nutrient flux to the strongest sink, usually knapweed. They displace many AMF beneficial to grass and affect knapweed nutrient allocation, biology, knapweed insects and probably root necrosis and emergence of ant buried seed. AMF determined nutrient root or shoot allocation determines nutrient shoot and root allocation and the benefit to root or seed-head insect species and whether C. diffusa is an annual–biannual or a semelparous perennial needing 5 or more years to flower. Both knapweeds do well without its AMF phylotypes without competition in fertile soil. In grass in Eurasia, they have a community of seven seed-head species segregated by head development stage. Prolonged seed dormancy buffered knapweed decline that resulted in release of a surfeit seed-head species. The presence of an eliasome on the seed and vigorous seedling clumps suggests burial by myrmecochorous ants with AMF supplied carbon supporting their growth. The root species community is segregated by habitat, climate, root part, and size. With larval induced compensatory growth and AMF nutrient sharing, the growth of plants with and without a larva was the same. On feeding completion, a nutrient out flux from the attacked plants reduced growth; but without killing. This needs a dual species or a repeated single species attack. Root species packing increases knapweed utilization; but the four approved species are insufficient for maximum utilization. Two additions are suggested. The aim of the paper is to provide enough understanding of the AMF and its plant and insect interactions to facilitate knapweed biological control and avoid past mistakes.     

Some aspects of biological and integrated control of pests

Zusammenfassung Der biologische und der chemische Aspekt der nützlingsschonenden Sch?dlingsbek?mpfung werden besprochen. Bezüglich des biologischen Aspektes wird Unterschied gemacht zwischen den Beziehungen zwischen importierten Sch?dlingen und ihre importierten natürliche Feinden einerseits und den Beziehungen zwischen autochtonen Sch?dlingen und ihren Raubfeinden, Parasiten und Hyperparasiten anderseits. Im letzten Falle sind die Hyperparasiten oft so zahlreich dass sie die Prim?r-parasiten fast eliminieren, jedenfalls ihre Wirkung stark vermindern. Wichtig ist weiter die kritische Populationsgrenze für die wichtigsten Sch?dlingsarten fest zu stellen damit wir wissen ob die Nützlinge im Stande sind sich zu behaupten als biologischer Bek?mpfungsfaktor. Der chemische Aspekt umfasst die Applikationen von selektiven Pflanzenschutzmitteln oder — Methoden zum Behalten der Nützlinge. Die integrierte Sch?dlingsbek?mpfung stimuliert und aktiviert die Entwicklung neuer Bek?mpfungsmethoden. Sie erfordert eine andere Einstellung des Forschers als die chemische Bek?mpfung. Zwei Arbeitsgruppen namentlich die Holl?ndische “Arbeitsgruppe für Harmonische Sch?dlingsbek?mpfung? und die ?Internationale Arbeitsgruppe für Integrierte Sch?dlingsbek?mpfung? der C.I.L.B. untersuchen in Holland, resp. in West-Europa und das Mittelmeergebiet die M?glichkeiten für eine integrierte Sch?dlingsbek?mpfung im Obstbau.      

Evaluating the efficacy of entomopathogenic nematodes for the biological control of crop pests: a nonequilibrium approach

The efficacy of entomopathogenic nematodes for biological control is assessed using deterministic models. Typically, the examination of such models involves stability analyses to determine the long-term persistence of control. However, in agricultural systems, control is often needed within a single season. Hence, the transient dynamics of the systems were assessed under specific, short-term control scenarios using stage-structured models. Analyses suggest that preemptive application may be the optimum strategy if nematode mortality rates are low; applying before pest invasion can result in greater control than applying afterward. In addition, repeated applications will suppress a pest, providing the application rate exceeds a threshold. However, the period between applications affects control success, so the economic injury level of the crop and the life history of the pest should be evaluated before deciding the strategy. In all scenarios, the most important parameter influencing control is the transmission rate. These findings are applicable to more traditional biological control agents (e.g., microparasites and parasitoids), and we recommend the approach adopted here when considering their practical use. It is concluded that it is essential to consider the specific crop and pest characteristics and the definition of control success before selecting the appropriate control strategy.     

Investigation of native isolates of entomopathogenic fungi for the biological control of three citrus pests

The pathogenicity of 15 isolates of Beauveria bassiana (Balsamo) Vuillemin, five isolates of Metarhizium anisopliae (Metschnikoff) Sorokin and one isolate of M. flavoviride (Gams and Rozsypal) were tested under laboratory conditions against the subterranean life stages of the citrus pests, Ceratitis rosa Karsch, C. capitata Wiedemann (Diptera: Tephritidae) and Thaumatotibia leucotreta Meyrick. (Lepidoptera: Tortricidae). When these citrus pests were treated with a concentration of 1×10⁷ conidia mL^?1, fungal isolates had a significantly greater effect on the adults of C. rosa and C. capitata than they did on the puparia of these two fruit fly species. Further, C. rosa and C. capitata did not differ significantly in their response to entomopathogenic fungi when adult and pupal mycosis were considered. Depending on fungal isolate, the percentage of T. leucotreta adults which emerged from fungal treated sand ranged from 5 to 60% and the percentage of pupae with visible signs of mycosis ranged from 21 to 93%. The relative virulence of the four most promising fungal isolates, as well as the commercially available B. bassiana product, BroadBand® (Biological Control Products, South Africa), were compared against one another as log-probit regressions of mortality against T. leucotreta which exhibited a dose-dependent response. The estimated LC₅₀ values of the three most virulent B. bassiana isolates ranged from 6.8×10⁵ to 2.1×10⁶ conidia mL^?1, while those of the least pathogenic ranged from 1.6×10⁷ to 3.7×10⁷ conidia mL^?1.     

An evolutionary perspective of biological invasions

The workshop on the Evolutionary Perspective of Biological Invasions in Terrestrial Ecosystems was held in Halle, Germany from 30 September to 3 October 2002.     

Analysis of importations for biological control of insect pests and weeds in New Zealand

Importations of biological control agents for insect pests and weeds in New Zealand are summarized and factors contributing to the relative success of the programmes are examined. The establishment rate of 30.9% is similar to that achieved worldwide, but is significantly lower than the rate achieved in the island habitat of Hawaii. The pioneering role of New Zealand in biological control is shown by the high proportion of programmes first attempted in this country. Although this novelty has not reduced the establishment rate, introductions against endemic species have not succeeded. Size of release was not a dominant feature in the establishment of agents. Complete or substantial success is recorded for 17 of the 70 target pests, with a relatively high success rate in forestry programmes. Examples of the influence of climate matching and competitive exclusion are also discussed. Changing practices and attitudes to the introduction of biological control agents are documented to show the increasing emphasis on specialists. No adverse effects of introductions are reported. The challenge to practitioners and regulators is to develop systems to evaluate conflicts of interest and develop workable mechanisms to determine which biological control agents are suitable for release.     

Selective flowers to enhance biological control of cabbage pests by parasitoids

Habitat management is an important element in sustainable agriculture and can be used to maximize a range of ecosystem services that support crop production. An important example of such ecosystem services is biological control of pests which can be enhanced by providing arthropod natural enemies with suitable floral resources. The potential risk of this approach, however, is that flowering plants may enhance the fitness of the targeted pests as well. We conducted experiments to identify selective plant species that would improve the longevity and parasitization rate of the parasitoid wasp Microplitis mediator without benefiting its host pest, the cabbage moth Mamestra brassicae. Effects on longevity were also assessed for Diadegma fenestrale, a generalist parasitoid wasp attacking lepidopteran pests. Additionally, we compared the effects of floral and extrafloral nectar, the latter being formed in some plant species and can significantly prolong the duration of nectar availability for natural enemies. Longevity of M. mediator and D. fenestrale as well as parasitization rates of M. mediator were significantly increased by the presence of Fagopyrum esculentum (floral nectar), Centaurea cyanus (floral and extrafloral nectar) and non-flowering Vicia sativa (extrafloral nectar). M. mediator parasitized 202.3 ± 29.7 M. brassicae larvae during its lifetime when presented F. esculentum, compared to 14.4 ± 3.4 larvae in the absence of floral resources. Extrafloral nectar of C. cyanus and V. sativa was as suitable for M. mediator as floral nectar and significantly increased longevity and parasitization rates. Longevity and fecundity of M. brassicae were not supported by the plant species tested. These results stress the importance of plant screening to achieve plant selectivity and to maximize biological control. F. esculentum, C. cyanus and V. sativa are recommended as selective plant species to enhance parasitoids of M. brassicae.     

BANKER PLANT携带天敌防治害虫的理论基础与应用

滥用农药导致粮食、蔬菜和水果内有毒农药高残留,严重威胁着人民的生命安全;利用生物防治害虫将提供更安全的食品和洁净的环境。Banker植物系统是利用非作物植物饲养及携带天敌的寄主或猎物,再利用天敌的寄主或猎物饲养和释放天敌。这些Banker植物就像是一个‘银行家(Banker)’,连续不断地供应‘货币’(天敌),使天敌从‘银行家’植物上扩散到有害虫的作物上防治害虫,是生物防治发展的一个重要方向。本文系统介绍了利用Banker植物为替代寄主饲养释放天敌防治害虫的最新进展,旨在推动我国更好地开展Banker植物系统及其相关理论与应用的研究。     

Efficiency of different egg parasitoids and increased floral diversity for the biological control of noctuid pests

Augmentative biological control of insects is a tool of Integrated Pest Management programs. In many agroecosystems, biological control is exercised largely by parasitoids, and it is found that the presence of food resources, as provided by flowering plants, can have a positive effect on survival, search ability and parasitism rate of parasitoid species. In Colombia, a recently established export crop, the cape gooseberry, is under continuous attack by a Lepidopteran species complex in the family Noctuidae. Our first objective was to test the longevity and parasitism rates of three species of egg parasitoids in the genus Trichogramma (Trichogramma atopovirilia Oatman & Platner, Trichogramma exiguum Pinto & Platner, and Trichogramma pretiosum Riley) for Spodoptera frugiperda Smith and Copitarsia decolora Gueené. Our results suggest that T. atopovirilia and T. pretiosum could be promising parasitoids for the control of S. frugiperda and C. decolora, with a percentage parasitism of between 30% and 60%, respectively. For our second objective, we selected T. atopovirilia as a model species to evaluate the effect of the presence of flowering plants on the longevity and parasitism rate in both, no choice and multiple choice experiments, under laboratory and field conditions. Our results consistently showed that the presence of red clover (Trifolium pratense L.) can increase the longevity and parasitism rate of T. atopovirilia, suggesting that providing food resources to parasitoids in cape gooseberry fields should be part of a habitat diversification strategy to control noctuid pests.     

Novel approaches for the study of vertebrate steroid hormone receptors

Steroid hormones are essential for the normal function of most organ systems in vertebrates. Reproductive activities in females and males, such as the differentiation, growth and maintenance of the reproductive system, require signaling by sex steroid hormones. Although extensively studied in mammals and a few fish and bird species, the evolution and molecular mechanisms associated with the nuclear steroid hormone receptors are still poorly understood in amphibians and reptiles. Given our interest in environmental signaling of sex determination as well as a major interest in environmental contaminants that can mimic steroid hormone signaling, we have established an approach to study the molecular function (ligand binding and trans-activation) of steroid hormone receptors cloned from reptiles. This approach involves molecular cloning and sequencing of steroid hormone receptors, phylogenic analysis and in vitro trans-activation assays using endogenous or exogenous ligands. Comparing the in vitro trans-activation induced by different ligands with receptors cloned from different species would develop additional functional relationships (classification) among steroid hormone receptors. This approach can provide insight into understanding why each species could have different responses to exogenous ligands. Further, we have developed a novel and less invasive approach to obtaining mRNA for molecular cloning and sequencing of steroid hormone receptors in reptiles and other non-mammalian species, using blood cells as a source of genetic material. For example, white blood cells (WBCs) and red blood cells (RBCs) of the American alligator both express steroid hormone receptors and have adequate amounts of mRNA for molecular cloning. This approach would allow us to analyze components of endocrine function of steroid hormones without sacrificing animals. Especially in endangered species, this approach could provide an understanding of endocrine functions, elucidate the phylogenic relationships of various receptors in vitro, such as the steroid hormone receptors, and determine possible effects of environmental contaminants in a minimally invasive manner.     

Management of orthopteran pests: a conservation perspective

Although the vast majority of orthopterans are not pests, some species have the potential to cause serious damage to human interests. Management of pest populations frequently conflicts with conservation of orthopteran species and processes, particularly when the pest species or its ecological processes are susceptible to extinction or when the pest population is coincident with non-target orthopterans. With respect to chemical control, the greatest hazards are the broad-spectrum, highly lethal properties of most agents, which can be mitigated with formulation and application methods. Biological control risks permanent, large-scale changes to orthopteran species and processes which can be minimized with bioinsecticidal and other short-lived or selective formulations and reliable host-range testing. Cultural control may have large-scale, broad-spectrum impacts to non-target orthopterans, but these hazards can be diminished by appropriate testing and monitoring. Mechanical control methods may be impractically labour intensive, but they are highly target specific and therefore warrant further consideration. Social control measures such as education, insurance and compensation programmes appear to have little direct potential for harm to orthopteran conservation, but the complex socioeconomic and, ultimately, environmental consequences of such programmes have not been assessed. The melding of orthopteran pest management and conservation requires that we perceive these insects and their ecological processes to be vital elements of sustainable agroecosystems. Our management of orthopterans (both non-target and pest populations) must focus on keeping good stewards on the land.     

Cross mating studies among five fruit fly parasitoid populations: potential biological control implications for tephritid pests

The reproductive compatibility between four different species/populations of the tephritid parasitoid Psyttalia (Walker) species from Kenya and individuals of the morphologically identical Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae) from a laboratory culture in Italy used in augmentative biological control of olive fly, Bactrocera oleae (Gmelin) (Diptera: Tephritidae) was assessed through cross mating tests using single-pair and group mating methods. Reciprocal crosses among the species resulted in the production of viable offsprings up to the second generation. In spite of the successful production of viable offspring in the laboratory, Psyttalia species are known to have specific host fruit and/or host fly preferences and populations/species may be isolated in one way or the other. However, it is not known whether these populations/species interbreed in the field. We discuss the ability of these parasitoids to interbreed and the potential effects of that on their use as biological control agents, especially in environments where other closely related species are present or in situations where multiple parasitoid introductions are intended.