What makes a successful biocontrol agent? A meta-analysis of biological control agent performance

We qualitatively reviewed the biocontrol literature in two major journals, Biological Control and Environmental Entomology, over the past 10 years by scoring 878 studies into 11 biocontrol-oriented questions. Quantitative meta-analyses were then used on data from 145 studies to examine the effects of different types of biocontrol agents (parasitoids, predators, and pathogens) on several attributes of weed and pest populations. Results for our qualitative review showed that most biocontrol studies were focused on lepidopteran pests, and that parasitoids were the most common biocontrol agents used. Our quantitative review showed that, for weeds, biocontrol agents significantly reduced weed biomass (−82.0%), flower (−98.9%), and seed production (−89.4%). For pests, our quantitative review showed that biocontrol agents significantly reduced pest abundance by 130% compared to control groups, increased parasitism (+139.0%) and increased overall pest mortality (+159.0%) compared to targets not exposed to biocontrol agents. Effects on pest mortality tended to be stronger for parasitoids than predators, although reductions caused in pest abundance were much stronger when predators were used as biocontrol agents. Addition of two or more biocontrol agents increased mortality by 12.97% and decreased pest abundance by 27.17% compared to single releases. Separate sets of meta-analyses demonstrated that the negative impacts of biocontrol on non-target species were much smaller than those for target species, although adverse effects of biocontrol on non-target organisms are based on small sample sizes and should be interpreted with caution. Our results also showed that biocontrol efficacy tended to be higher when agents were generalists than when they were specialists. Large fail–safe numbers found for most of the estimated effects indicate the robustness of the results found for the efficacy of biological control programs.     

A Keystone Ant Species Provides Robust Biological Control of the Coffee Berry Borer Under Varying Pest Densities

Species’ functional traits are an important part of the ecological complexity that determines the provisioning of ecosystem services. In biological pest control, predator response to pest density variation is a dynamic trait that impacts the provision of this service in agroecosystems. When pest populations fluctuate, farmers relying on biocontrol services need to know how natural enemies respond to these changes. Here we test the effect of variation in coffee berry borer (CBB) density on the biocontrol efficiency of a keystone ant species (Azteca sericeasur) in a coffee agroecosystem. We performed exclosure experiments to measure the infestation rate of CBB released on coffee branches in the presence and absence of ants at four different CBB density levels. We measured infestation rate as the number of CBB bored into fruits after 24 hours, quantified biocontrol efficiency (BCE) as the proportion of infesting CBB removed by ants, and estimated functional response from ant attack rates, measured as the difference in CBB infestation between branches. Infestation rates of CBB on branches with ants were significantly lower (71%-82%) than on those without ants across all density levels. Additionally, biocontrol efficiency was generally high and did not significantly vary across pest density treatments. Furthermore, ant attack rates increased linearly with increasing CBB density, suggesting a Type I functional response. These results demonstrate that ants can provide robust biological control of CBB, despite variation in pest density, and that the response of predators to pest density variation is an important factor in the provision of biocontrol services. Considering how natural enemies respond to changes in pest densities will allow for more accurate biocontrol predictions and better-informed management of this ecosystem service in agroecosystems.     

Incorporating ecologically relevant measures of pesticide effect for estimating the compatibility of pesticides and biocontrol agents

The compatibility of biological control agents with pesticides is a central concern in integrated pest management programs. The most common assessments of compatibility consist of simple comparisons of acute toxicity among pest species and select biocontrol agents. A more sophisticated approach, developed by the International Organisation of Biological Control (IOBC), is based on a tiered hierarchy made up of threshold values for mortality and sublethal effects that is used to determine the compatibility of pesticides and biological control agents. However, this method is unable to capture longer term population dynamics, which is often critical to the success of biological control and pest suppression. In this article, we used the delay in population growth index, a measure of population recovery, to investigate the potential impacts that the threshold values for levels of lethal and sublethal effects developed by the IOBC had on three biocontrol agents: sevenspotted lady beetle, Coccinella septempunctata L.; the aphid parasitoid Diaeretiella rapae (M'Intosh), and Fopius arisanus (Sonan), a parasitoid of tephritid flies. Based on life histories of these economically important natural enemies, we established a delay of 1-generation time interval as sufficient to disrupt biological control success. We found that delays equivalent to 1-generation time interval were caused by mortality as low as 50% or reductions of offspring as low as 58%, both values in line with thresholds developed by the IOBC. However, combinations of mortality and reduction of offspring lower than these values (from 32 to 43% each) over a simulated 4-mo period caused significant population delays. Furthermore, the species used in these simulations reacted differently to the same levels of effect. The parasitoid D. rapae was the most susceptible species, followed by F. arisanus and C. septempunctata. Our results indicate that it is not possible to generalize about potential long-term impacts of pesticides on biocontrol agents because susceptibility is influenced by differences in life history variables. Additionally, populations of biocontrol agents may undergo significant damage when mortality approaches 50% or when there is mortality of -30% and a 30% reduction in offspring caused by a sublethal effect. Our results suggest that more ecologically relevant measures of effect such as delays in population growth may advance our knowledge of pesticide impacts on populations of beneficial species.     

Survival of Conidia of Clonostachys rosea on Stored Barley Seeds and Their Biocontrol Efficacy Against Seed-borne Bipolaris sorokiniana

Survival and biocontrol activity of Clonostachys rosea (isolate IK726) conidia during storage on barley seeds were investigated. The initial density of colony forming conidia on seed was 4 &#50 10 3 to 9 &#50 10 4 colony forming units (cfu)/seed. After 5 months storage at 4°C, the density decreased by less than one order of magnitude and the biocontrol efficacy against seedling blight caused by seed-borne Bipolaris sorokiniana was maintained at a significantly high level ( > 80% disease reduction) for > 5 months. Conidial survival on seeds stored at 20°C declined more rapidly than at 4°C, and biocontrol efficacy was significantly reduced after 3-5 months. However, conidia produced on solid media over 20 days survived better than conidia produced in liquid culture and conidia from solid media produced over 12 days. In contrast, when seeds treated with conidia were packed with silica gel and stored at 20°C, the cfu density decreased by less than one order of magnitude after 5 months and the biocontrol efficacy was still high after 6 months. A dose-response curve revealed that 103 cfu/seed were needed for 80% control of seedling blight. Similar control was obtained in storage experiments when approximately 103 cfu/seed were recovered from seed, indicating that conidia which survived also retained a high ability to control disease.     

Contrasting the farm-scale spatio-temporal dynamics of boundary and field overwintering predatory beetles in arable crops

In many European countries agri-environment funding can improve ecosystem services, including the adoption of conservation biocontrol, through the creation of habitats that encourage beneficial arthropods. Predatory beetles are amongst the most numerous and diverse arthropods present in arable fields. The primary ecosystem services provided by predatory beetles are in biological control and food chain maintenance as they are a key resource for many higher organisms. However, to be effective biological control agents, able to respond quickly to wherever a pest infestation occurs, then they must be sufficiently abundant and widely distributed. Conservation biocontrol utilising predatory beetles has focussed on the impact of species that overwinter in adjacent field boundaries, although those overwintering within fields are often more abundant. If the abundance and distribution of predatory beetles is to be maximised then further knowledge of their spatial dynamics is required to ensure habitats are arranged appropriately. The spatio-temporal dynamics of boundary and field overwintering species was measured across 64 ha encompassing six fields and for three consecutive years using a grid of 973 pitfall traps. Boundary species were more numerous in spring (May and June) whereas more field species were captured in July. The species composition was comprised of relatively few taxa. Boundary species occurred in small patches that were distributed across the fields in spring, but were only found close to the margins in July. Patches persisted in some locations over two years. Field species occurred in larger patches, spread across particular fields and these were stable within years and to some extent between years. Game-cover strips were attractive to boundary species in the spring and summer and did not effect predator distribution in the adjacent crop. Handling Editor: Eric Lucas.     

After biocontrol: Assessing indirect effects of insect releases

Development of biological control agents for weeds has been motivated by the need to reduce the abundance and distribution of a pest plant where chemical and mechanical control were not cost effective. Primary objectives have been direct reduction in abundance of the target and, secondarily, the increase of desirable species. Recently, wildland weeds have become a focus of biological control projects. Here, desired outcomes include both reduction of the target and indirect effects of increased diversity and abundance of native species and restoration of ecosystem services. However, goals and benefits of biocontrol programs are not always well-articulated and direct and indirect impacts are not easily predicted. We evaluated the extent to which several successful biological control projects for weeds of rangelands and waterways measured indirect impacts on invaded ecosystems. We also examined biocontrol of a wildland pest tree for which the principal objective is restoration of ecosystem services. We found few quantitative assessments of the impacts of pest plant reduction on community composition or ecosystem processes. All examples documented variation in the impacts of agent(s) across the invasive range of the target plant as well as variation in impacts on the invaded ecosystem. However, without appropriate quantitative information, we cannot evaluate site characteristics that may influence vegetation responses. Most successful weed management programs integrated the use of biocontrol agents with other weed management strategies, especially modifications of disturbance and competing vegetation. Discussion and evaluation of responses of nontarget species would improve our understanding of the context-specificity of outcomes.     

Preliminary In Vitro Insights into the Use of Natural Fungal Pathogens of Leaf-cutting Ants as Biocontrol Agents

Leaf-cutting ants are one of the main herbivores of the Neotropics, where they represent an important agricultural pest. These ants are particularly difficult to control because of the complex network of microbial symbionts. Leaf-cutting ants have traditionally been controlled through pesticide application, but there is a need for alternative, more environmentally friendly, control methods such as biological control. Potential promising biocontrol candidates include the microfungi Escovopsis spp. (anamorphic Hypocreales), which are specialized pathogens of the fungi the ants cultivate for food. These pathogens are suppressed through ant behaviors and ant-associated antibiotic-producing Actinobacteria. In order to be an effective biocontrol agent, Escovopsis has to overcome these defenses. Here, we evaluate, using microbial in vitro assays, whether defenses in the ant-cultivated fungus strain (Leucoagaricus sp.) and Actinobacteria from the ant pest Acromyrmex lundii have the potential to limit the use of Escovopsis in biocontrol. We also explore, for the first time, possible synergistic biocontrol between Escovopsis and the entomopathogenic fungus Lecanicillium lecanii. All strains of Escovopsis proved to overgrow A. lundii cultivar in less than 7 days, with the Escovopsis strain isolated from a different leaf-cutting ant species being the most efficient. Escovopsis challenged with a Streptomyces strain isolated from A. lundii did not exhibit significant growth inhibition. Both results are encouraging for the use of Escovopsis as a biocontrol agent. Although we found that L. lecanii can suppress the growth of the cultivar, it also had a negative impact on Escovopsis, making the success of simultaneous use of these two fungi for biocontrol of A. lundii questionable.     

Local adaptation to biocontrol agents: A multi-objective data-driven optimization model for the evolution of resistance

Spatial and temporal variability in the application of biological control agents such as parasites or pathogenic bacteria can cause the evolution of resistance in pest organisms. Because biocontrol will be more effective if organisms are not resistant, it is desirable to examine the evolution of resistance under different application strategies.We present a computational method that integrates a genetic algorithm with experimental data for predicting when local populations are likely to evolve resistance to biocontrol pathogens. The model incorporates parameters that can be varied as part of pest control measures such as the distribution and severity of the biocontrol agent (e.g., pathogenic fungi). The model predicts the evolution of pathogen defense as well as indirect selection on several aspects of the organism's genetic system. Our results show that both variability of selection within populations as well as mean differences among populations are important in the evolution of defenses against biocontrol pathogens. The mean defense is changed through the pest organism's genotype and the variance is affected by components of the genetic system, namely, the resiliency, recombination rate and number of genes.The data-driven model incorporates experimental data on pathogen susceptibility and the cost of defense. The results suggest that spatial variability rather than uniform application of biological control will limit the evolution of resistance in pest organisms.     

Invertebrate pests and diseases of sweetpotato (Ipomoea batatas): a review and identification of research priorities for smallholder production

Sweetpotato has been the subject of little research worldwide compared with other major crop staples, and this is especially so for less developed countries where sweetpotato is critical for food security. This review synthesises information on plant protection issues that affect smallholder sweetpotato farmers in less developed countries to identify major issues and suggest research priorities. Though the pests and diseases of sweetpotato in less developed countries are largely common to industrialised systems, their relative importance differs and losses tend to be more severe as a result of differing agronomic practices and relative unavailability of management options and technical support that are important in developed countries. Smallholders are heavily reliant on cultural practices such as traditional forms of biological control using ants and livestock, fallowing and composting (sometimes with plant materials having biocidal properties). Crop protection methods that have been developed for use in sweetpotato production in developed countries, such as pathogen‐tested planting material, early maturing varieties, pheromone trapping and pesticides are less accessible to, and relevant for, smallholders. Smallholders also typically harvest a given crop progressively which extends the period over which storage roots are potentially vulnerable to attack but reduces the risk of post‐harvest losses. Human population growth in developing countries is leading to an increase in cropping intensity with shorter fallow periods and more years of continuous crops. This has the dual effect of depleting soil nutrients and increasing the potential for pest and pathogen build‐up. Associated with this, the adoption of strategies to manage crop nutrition, such as not burning crop residues, promote carryover of pests and pathogen inocula. As a consequence of these factors, sweetpotato yield losses from diseases, especially viruses, and pests, particularly weevils, can be high. Climate change is likely to result in more frequent drought and this will increase losses caused by sweetpotato weevils that are favoured by dry conditions. This review of sweetpotato pests and their management options concludes with suggestions for some future research priorities including the combination of traditional practices that have pest management outcomes with relevant practices from industrial production that are able to be transferred or modified for use in smallholder production. Increased technical support for decision making and diagnostics, including molecular approaches that have scope for field use, will be important in reducing the burden imposed by biotic threats to this important global crop.     

The effects of wheat-pea mixed intercropping on biocontrol potential of generalist predators in a long-term experimental trial

Arthropod generalist predators can be effective natural control agents of pests and weeds in agroecosystems. Their activity and contribution to biocontrol may increase in response to more complex agricultural habitats. In this study, we investigated the effects of winter wheat-pea mixed intercropping on the biocontrol potential of generalist predators compared with the respective mono-crops. We evaluated not only the effects during the intercropping season but also the pre-crop values of the mixture for the subsequent barley crop. Furthermore, we evaluated the influence of different long-term soil organic carbon and fertility management regimes on activity and biocontrol potential of predators. Field work was conducted over two seasons in a field experiment located in Gembloux, Belgium. A set of proxies for ecosystem functions were measured using the Rapid Ecosystem Function Assessment approach. We measured attack and predation rates of sentinel prey and weed seeds artificially placed in the field. Furthermore, we assessed activity density of the main groups of generalist predators during the exposure of the baits. Our results showed that crop type affected activity and biocontrol potential of predators. Predation rates were much lower in wheat than pea and wheat-pea. The mixture wheat-pea had a positive effect on predator activity density compared to wheat mono-crop, while pea supported an intermediate activity of epigeal predators. In the second season of the field work, we found the highest biocontrol potential by predators in barley plots cultivated after pea. Finally, our results failed to find any differences in biocontrol potential of predators between long-term soil organic carbon and fertilisation management strategies. These results suggest that crop type has a major relevance in influencing the activity of generalist predators, and the mixed intercropping wheat-pea may represent a valid strategy to enhance biological pest control in comparison to wheat cultivated as mono-crop. Furthermore, we show that the cultivation of pea as mono-crop may have an important pre-crop value within the rotation increasing the provision of ecosystem services such as biocontrol.     

Excitable Population Dynamics,Biological Control Failure,and Spatiotemporal Pattern Formation in a Model Ecosystem

Biological control has been attracting an increasing attention over the last two decades as an environmentally friendly alternative to the more traditional chemical-based control. In this paper, we address robustness of the biological control strategy with respect to fluctuations in the controlling species density. Specifically, we consider a pest being kept under control by its predator. The predator response is assumed to be of Holling type III, which makes the system’s kinetics “excitable.” The system is studied by means of mathematical modeling and extensive numerical simulations. We show that the system response to perturbations in the predator density can be completely different in spatial and non-spatial systems. In the nonspatial system, an overcritical perturbation of the population density results in a pest outbreak that will eventually decay with time, which can be regarded as a success of the biological control strategy. However, in the spatial system, a similar perturbation can drive the system into a self-sustained regime of spatiotemporal pattern formation with a high pest density, which is clearly a biological control failure. We then identify the parameter range where the biological control can still be successful and describe the corresponding regime of the system dynamics. Finally, we identify the main scenarios of the system response to the population density perturbations and reveal the corresponding structure of the parameter space of the system. A. Morozov is on leave from Shirshov Institute of Oceanology, Russian Academy of Science, Nakhimovsky Prosp. 36, Moscow 117218, Russia.     

Biological control of insects in Brazil and China: history,current programs and reasons for their successes using entomopathogenic fungi

Brazil and China have been successful in the use of microbial control methods to manage several agricultural and forest insects. In both countries, entomopathogenic fungi (EF) have been used for pest management since the 1970s. However, EF production and commercialization have not been constant in either country. Several companies and cooperatives suspended their activities or shut down from the 1970s to the 1990s. This was due to loss of confidence in available mycoinsecticides by Brazilian farmers or due to reduced involvement and government subsidies for biological control in China; and, consequently, mycoinsecticides were largely replaced by inexpensive chemical insecticides. Starting in the 1990s and continuing until today, however, new Brazilian and Chinese private companies have arisen. In Brazil, the area treated with M. anisopliae for spittlebug control alone is estimated to be approximately one million hectares in 2008, 75% of which was for control of spittlebugs in sugarcane plantations and the remainder for spittlebugs in pasture grass (primarily Brachiaria spp.) and other smaller programs. In China, the fungus Beauveria bassiana was used annually in 0.8–1.3 million ha until the 1980s. Several factors were important for the success of these programs, such as: governmental support (at least during the initial steps of biocontrol programs); availability of indigenous virulent fungal isolates; low-cost substrates for mass production; retail prices of mycoinsecticides lower than their chemical counterparts; and sale by contract which allows the products to be immediately available for use, rather than stored. In this report, we discuss the current biocontrol programs using insect fungi in these two developing countries, as well as the future and main challenges they must face to further encourage the adoption of mycoinsecticides.     

Natural enemies of Tuta absoluta in the Mediterranean basin,Europe and South America

The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) represents a global threat to commercial tomato (Solanum lycopersicum L.) production, both in open field and greenhouse. Native to South America, it spread over the Mediterranean Basin, Europe, Africa and part of Asia in only 12 years, and currently it is reported in over 80 countries. Biological control is one of the options for its control and a large number of natural enemies has been reported in association with the pest, both in the areas of origin and of introduction. The egg parasitoid Trichogramma pretiosum, in South America, and the mirid predators Macrolophus pygmaeus and Nesidiocoris tenuis, in Europe and the Mediterranean basin, are used as commercial biocontrol agents. Even if several natural enemies might be promising candidates for biocontrol, their potential role in quantitative pest reduction has been seldom established under practical tomato production conditions.

Since climatic suitability indices predict a high probability for continued invasion by T. absoluta, mainly in China and the USA, there is an urgent need for new control options. In order to minimise the use of broad spectrum insecticides, biocontrol techniques should be considered. As tomato is produced seasonally, augmentative biocontrol seems to be the most effective control option, but pest reduction might be optimised by adding conservation biocontrol, and by combining biocontrol within IPM programmes.

Here, an overview of predators and parasitoids of T. absoluta in South American and Euro-Mediterranean regions, and their biological control efficacy under laboratory, semi-field and field conditions is provided.     

A comparison of management options for leatherjacket populations in organic crop rotations using mathematical models

1 Pest management in organic systems is challenged by the paucity of options for direct interventions to control damaging populations compared with conventional agriculture. Consequently, a greater emphasis has to be placed on managing pest numbers through a rotation. In the present study, simulation modelling is used to evaluate the effects of different management options on populations of Tipula paludosa (leatherjackets) in organic rotations.
2 The growth of leatherjacket populations in grass was simulated over 5 years for different starting numbers. A significant risk of leatherjacket attack to subsequent crops can be avoided by limiting the fertility building phase of a rotation to a maximum of 2 years.
3 The effect of cultural control through additional cultivation interventions was compared in rotations comprising a grass/clover fertility building phase with host and/or nonhost crops. It is concluded that the effects are marginal and that prophylactic use cannot be recommended.
4 The prophylactic use of biological control agents in permanent grass and grass/arable rotations was investigated. Maximum population reductions in grass were achieved through annual autumn applications but the optimal economic strategy was less frequent than this. Application in the autumn preceding a spring-sown arable crop provided the best risk reduction.
5 A model decision support system for the control of pests in organic systems using data for leatherjacket damage to spring barley is presented. Economic threshold concepts are used to define when cultural control (as additional cultivation) and biocontrol applications should be used.
6 The present study shows the potential benefits of simulation modelling for the rapid evaluation of a wide range of pest management options. Any conclusions drawn from such simulations, however, are provisional until they can be tested experimentally.     

A meta-analysis of biocontrol potential and herbivore pressure in olive crops: Does integrated pest management make a difference?

Agricultural policies in the European Union (EU) are increasingly promoting organic management and integrated pest management (IPM) as environmentally friendly alternatives to high-input conventional management. While there is consensus that organic management is largely beneficial for biodiversity, including the natural enemies of crop pests, IPM has been much less scrutinized. We conducted a meta-analysis based on 294 observations extracted from 18 studies to compare the effects of conventional, IPM and organic management on biocontrol potential and herbivore pressure in olive, an important cash crop in the EU. Information about the management practices used was also compiled to assess differences in intensity between the three management strategies. Results suggest that IPM is predominantly based on intensive practices, employing chemical control rather than preventive measures as a first resort. Biocontrol potential and herbivore pressure were similar in conventional management and IPM. Moreover, biocontrol potential was higher in organic crops than in crops under IPM, especially when considering canopy-dwelling natural enemies. Although organic management enhanced biocontrol potential, it also benefitted some olive pests, and in both cases effects were more pronounced at warmer temperatures. Our results suggest that, in its current form, IPM might not significantly affect biocontrol potential or herbivore pressure when compared with conventional olive crop management. A shift to a more comprehensive implementation of IPM practices is thus needed, involving the use of proactive measures to promote natural enemies and regulate olive pests before resorting to chemical control. Moreover, greater use of non-chemical inputs might be required for effective regulation of olive pests in organic olive crops.     

Life stage and population density of Plutella xylostella affect the predation behavior of Euborellia annulipes

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is the main pest of brassica crops worldwide. The ringlegged earwig, Euborellia annulipes (Lucas) (Dermaptera: Anisolabididae), has been reported as a potential predator of lepidopteran larvae, including this pest, and may therefore be used for biological control. Knowledge about predator–prey interactions is important to establish pest management strategies. Therefore, the objective of this work was to evaluate the influence of the developmental stage (larva and pupa) and density of P. xylostella on the preference and functional response of E. annulipes adult females. We used choice and no‐choice tests to evaluate the foraging behavior and preference of E. annulipes on DBM life stages and varied prey density to assess the type of functional response of the ringlegged earwig. Larvae were preferred over pupae, and the predator’s functional response was type II for both prey stages. Our results report the potential of E. annulipes as a biocontrol agent of P. xylostella. Understanding their interactions may help in decision‐making and optimization of integrated management strategies.     

Safety of Microorganisms Intended for Pest and Plant Disease Control: A Framework for Scientific Evaluation

Microorganisms are enormous but largely untapped natural resources for biological control of pests and diseases. There are two primary reasons for their underployment for pest or disease control: (1) the technical difficulties of using microorganisms for biological control, owing to a lack of fundamental information on them and their ecology, and (2) the costs of product development and regulatory approvals required for each strain, formulation, and use. Agriculture and forestry benefit greatly from the resident communities of microorganisms responsible for naturally occurring biological control of pest species, but additional benefits are achieved by introducing/applying them when or where needed. This can be done as (1) an inoculative release, (2) an augmentative application, or (3) an inundative application. Because of their specificity, different microbial biocontrol agents typically are needed to control different pests or the same pest in different environments. Four potential adverse effects are identified as safety issues (hazards) associated with the use of microorganisms for the biological control of plant pests and diseases. These are: (1) displacement of nontarget microorganisms, (2) allergenicity to humans and other animals, (3) toxigenicity to nontarget organisms, and (4) pathogenicity to nontarget organisms. Except for allergenicity, these are the same attributes that contribute to the efficacy of microbial biocontrol agents toward the target pest species. The probability of occurrence of a particular adverse nontarget effect of a microbial biocontrol agent may be a function of geographic origin or a specific trait genetically added or modified, but the safety issues are the still the same, including whether the microorganism intended for pest or disease control is indigenous, nonindigenous (imported and released), or genetically modified by traditional or recombinant DNA (rDNA) technology. Likewise, the probability of occurrence of a particular adverse nontarget effect may vary with method of application, e.g., whether as an aerosol, soil treatment, baits, or seed treatment, and may increase with increased scale of use, but the safety issues are still the same, including whether the microorganism is used for an inoculative release or augmentative or inundative application. Existing practices for managing microorganisms in the environment (e.g., plant pathogens,Rhizobium,plant inoculants) provide experience and options for managing the risks of microorganisms applied for pest and disease control. Moreover, experience to date indicates that any adverse nontarget effects, should they occur, are likely to be short-term or transitory effects that can, if significant, be eliminated by terminating use of the microbial biocontrol agent. In contrast, production agriculture as currently practiced, such as the use of tillage and crop rotations, has significant and long-term effects on nontarget organisms, including the intentional and unintentional displacement of microorganisms. Even the decision to leave plant pests and diseases unmanaged could have significant long-term environmental effects on nontarget organisms. Potential safety issues associated with the use of microbial biocontrol must therefore be properly identified and compared with the impact of other options for managing the pest or leaving the pest unmanaged. This paper provides a scientific framework for this process.     

Effect of long-term cold storage on the fitness of pre-wintering <Emphasis Type="Italic">Harmonia axyridis</Emphasis> (Pallas)

The multicolored Asian ladybird beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is considered an important generalist predator that can be used as a biological control agent against Hemiptera Sternorrhyncha, Thysanoptera, and the eggs and larvae of Lepidoptera, Coleoptera and Diptera. There are currently abundant natural resources of overwintering H. axyridis in Asia and North America. Given its potential as a biological control agent, methods can be developed to increase its effectiveness for pest control. The availability of an adequate cold storage method would enable the use of field-collected pre-wintering ladybirds for pest suppression in the following season. We studied the effect of cold storage (30, 60, 90, 120 and 150 days stored at −3, 0, 3 and 6°C) on survival, fecundity and predation in field-collected populations. The survival of both female and male ladybirds decreased significantly as storage duration increased at −3°C and 0°C. The ladybirds showed more than 80% survival when they were stored for 150 days at 3°C and 6°C. Long-term cold storage had different effects on the fecundity of H. axyridis at different temperatures. Prolonged cold storage at both 3°C and 6°C shortened pre-oviposition duration and had no adverse effect on reproductive capacity as compared to that of unstored individuals. The adults that experienced 90-day storage at 0°C had the shortest pre-oviposition duration and the largest reproductive capacity. The individuals that were stored for 150 days at 3°C consumed significantly more aphids than the unstored ones. Generally, 3–6°C is a suitable temperature for cold storage of the ladybird without any reduction in fitness. This study will help the exploitation and application of pre-wintering H. axyridis for the biological control of insect pests.     

Insect pest management in African agriculture: Challenges in the current millenium

Pest management on a global scale experienced a total revolution after World War II when synthetic organic compounds were in agriculture and public health. However, it soon became apparent that there were many limitations in the use of chemicals for pest management. In agriculture, problems of pest resurgence, secondary pest outbreaks, pest resistance and adverse effects of pesticides on the environment, including human poisoning and toxicity to other non-target organisms, led to the search for alternative approaches to the pest outbreak problem. The 1960s produced new ideas on integrated pest management (IPM) strategies, followed by intensification of the search for biological control agents, which could be incorporated into IPM programmes. New application technologies were developed in the 1970s and 1980s and ecological approaches to the pest problem were spearheaded in the developed world in the 1990s, with extensive studies focused on the whole ecosystem. Important advances in crop production have also taken place in Africa in this century, involving adoption of high yielding varieties, fertilizer application, intensification of crop protection approaches, less shifting cultivation and more mono-cropping systems. However, these advances have led to increasing pest problems which unless tackled imaginatively and intelligently, they could become the most important constraint in crop production in the present millennium. Africa has entered the current millennium with relatively underdeveloped agriculture on a global scale and little investment in research on new pest management technologies that could be used to reduce crop losses. We are still highly dependent on pesticides for pest management. Therefore, the greatest challenges in agriculture in Africa will be the switch from a pesticide based mode of reducing losses due to pests to one that is ecosystem based, making use of insect management techniques which are ecologically and economically sound. Specifically, some of the major challenges in pest management in agriculture in Africa include; (i) reducing the dependence on pesticides, thus avoiding the limitations observed in the past 50 years; (ii) overcoming ignorance of the pest species and their associated community of parasites and predators which has dire consequences on the whole ecosystem; (iii) keeping out exotic pests, which in this millennium have had a devastating blow on the production of some crops and (iv) developing indigenous technologies for pest management (IPM, biocontrol, etc.) and making available to farmers materials for pest management which are affordable, safe, effective and environmentally friendly (e.g. microbial, botanicals, pheromones, genetically engineered products etc.). Both legislative and quarantine measures will have a significant role to play in pest management in the next millennium, but only when practised on a wider geographical area. Information technology (IT) will affect the way we acquire and make use of pest management strategies. Africa is therefore faced with the challenge of building up and improving its infrastructure and expertise on IT if it is to benefit pest management on the continent.     

Biological control of marine invasive species: cautionary tales and land-based lessons

Biological control (biocontrol) has successfully regulated pest populations in terrestrial agroecosystems, but it has also caused negative unintended consequences for native species. Marine biologists and resource managers have recently published a growing number of proposals to include biocontrol in integrated pest management programs in oceans, seas and estuaries. Here, I review six ecologically and taxonomically diverse case studies of marine biocontrol programs at various stages of planning and implementation. Proposals include viral or microbial control of harmful algal blooms, predatory control of the ctenophore Mnemiopsis leidyi in the Black Sea, parasitic regulation of the European green crab Carcinus maenas, castration by ciliates of the seastar Asterias amurensis in Australia, herbivory of the toxic green alga Caulerpa taxifolia in the Mediterranean by sacoglossan sea slugs, and insect biocontrol by the planthopper Prokelesia marginata to ameliorate ecological impacts of the saltmarsh cordgrass Spartina alterniflora. Where data exist, I evaluate these examples in terms of lessons marine invasion biologists can glean from the rich history of terrestrial biocontrol, and explicitly contrast agroecosystems with invaded marine habitats. Host specificity cannot be guaranteed in the marine biocontrol proposals examined. Feasible alternatives to classical biocontrol in the marine realm should be emphasized, including more investment in invasion prevention tools, early detection and eradication while invasions are small, and increased attention to native natural enemies to control exotic pests. Biocontrol in marine habitats is risky: it poses many more uncertainties and has a much sparser history than its counterpart on land.