Dear Udari and others interested in this discussion,

In my opinion, field release of biological control agents should not be done without a risk assessment (and indeed this is usually done), and in that case it is in most cases more sustainable and specific than application of pesticides. The specificity can be maximized by using specialist natural enemies rather than generalists, which minimizes the risk of non-target effects. Indeed such specificity is one of the major assets of biological control, next to the minimization of pesticide-load in the environment, and the lower likelihood of the evolution of resistance (as is very common with the use of pesticides). On the other hand, one of the main reasons why pesticides are still commonly used in favour of biological control, is the time lag with biological control: with pesticides, the organisms drop dead almost immediately (if well applied), whereas with biological control, a farmer does not actually see, for example, pest insects dropping dead immediately, but only after the enemy has established and attained the required population size to suppress or eliminate the pest. Weighing the cons and pros, I feel that biological control, supported by a good risk assessment and scientific study on optimal application, is by far preferable over pesticides in most cases. Examples are known where the use of pesticides is actually aggravating the problem, e.g. in rice culture. On the other hand, one of the best examples of succesful use of biological control is that of the cassava mealybug in Africa, which has been at least suppressed to sub-pest status by employing parasitoid wasps, eg. Epidinocarsis lopezi. But, the example of the release of the Asian multicoloured ladybird beetle, Harmonia axyridis, in the USA and Europe to control aphid pests, after which the ladybird itself has reached pest status on both continents, illustrates that appropriate research and risk assessment is crucial. I would stongly advocate the allocation of more resources for research on the development of such risk assessment protocols, and optimization of the use of the biocontrol agents, for a sustainable pest control.

A quite general question. Biologicals can work better, equal to or less effective than chemicals on the field. Application of biologicals can be more or less laborious/complicate compared to chemicals. The application costs of biologicals are in many cases higher than for chemicals. Many biologicals have a more specific mode of action than chemicals; sometimes you can target (only) a single pest species. Therefore, any kind of side effects are usually lower than for chemicals.

According to Brian B. Mc Spadden Gardener. biological control of plant pests and pathogens continues to inspire research and development in many fields. Plant pathogens are just one class of targets of biological control, which also is designed to limit other pests such as insects, parasitic nematodes, and weeds. In the narrowest sense, biocontrol involves suppressing pest organisms with other organisms. However, the interrelationships of many environmental variables can result in multiple interactions among organisms and their environment, several of which might contribute to effective biological control. Furthermore, natural products and chemical compounds discovered as a result of basic research into the molecular mechanisms of pathogenesis and biological control have led to the development of “biorational” pesticides. Here, we use the term biological control in the broader sense as we describe the current status of research, commercial development, and application of biocontrol strategies targeted at plant pathogens.

Over the past one hundred years, research has repeatedly demonstrated that phylogenetically diverse microorganisms can act as natural antagonists of various plant pathogens. The interactions between microorganisms and plant hosts can be complex. Interactions that lead to biocontrol can include antibiosis, competition, induction of host resistance, and predation. Research on the mechanisms of biocontrol employed by effective bacterial strains has revealed a variety of natural products that can be exploited for the development of chemical control measures.

A variety of research questions remain to be fully answered about the nature of biological control and the means to most effectively manage it under production conditions. Advanced molecular techniques are now being used to characterize the diversity, abundance, and activities of microbes that live in and around plants, including those that significantly impact plant health. Still, much remains to be learned about the microbial ecology of both plant pathogens and their microbial antagonists in different agricultural systems. Fundamental work remains to be done on characterizing the different mechanisms by which organic amendments reduce plant disease. More studies on the practical aspects of mass-production and formulation need to be undertaken to make new biocontrol products stable, effective, safer and more cost-effective.

Interest in biological control research continues reflecting the desire of multiple constituencies to develop sustainable methods for controlling plant disease. Growing concerns about environmental health and safety have led to substantial regulatory changes in the past several years.

Successful application of biological controls requires more knowledge-intensive management. To this end, extension personnel and growers must also become more fully aware of the costs and benefits that biopesticides can provide. Understanding when and where biological control of plant pathogens can be profitable requires an appreciation of its place within integrated pest management systems. For this purpose, the model of a pyramid can be used to highlight the way growers might productively construct their pest management programs.

The foundation of a sound pest and disease management program in an annual cropping system begins with sound cultural practices that alter the farm landscape to promote crop health. These include crop rotations that limit the availability of host material used by plant pathogens. Judicious use of tillage can disrupt pest and pathogen life cycles, bury weeds, and prepare seed beds of optimal moisture and bulk density. Careful management of soil fertility and moisture can also limit plant disease by minimizing plant stress. In nurseries and greenhouses, environmental control can be more tightly regulated in terms of temperature, light, moisture, and soil composition (i.e., peat-based potting mixes), but the design of such systems cannot wholly eliminate pest problems.

The second layer of defense against pests consists of the quality of crop germplasm. Breeding for pathogen resistance contributes substantially to crop success in most regions. Newer technologies that directly incorporate genes into crop genomes, commonly referred to as genetic modification or genetic engineering, are bringing new traits into crop germplasm. The most-widely distributed of these plant-incorporated protectants (PIPs) are the different insecticidal proteins derived from Bacillus thuringiensis. Other technologies, such as seed washing, testing for pathogens, and treatment are also used to keep germplasm pathogen-free. In perennial cropping systems, such as orchards and forests, germplasm quality may be more important than cultural practices, because rotation and tillage cannot be used as regularly. Upon these two layers, growers can further reduce pest and pathogen pressure by considering both biological and chemical inputs.

Biologically-based inputs such as pheromone traps and microbial pesticides can be used to interfere with pest activities. Registered biopesticides are generally labeled with short reentry intervals (REI) and pre-harvest intervals (PHI), giving greater flexibility to growers who need to balance their operational requirements and pest management goals. When living organisms are introduced, they may also augment natural beneficial populations to further reduce the damage caused by targeted pathogens or pests.

Finally, synthetic chemicals may be added to limit crop damage by pests and pathogens. Because of growing concerns about health and environmental safety, the use of toxic, carcinogenic, and/or environmentally damaging chemicals is currently being discouraged. Within the context of IPM programs, the use of such chemicals should be considered only after other management options have been fully implemented.

Clearly, the different levels described here are not entirely independent of one another. Indeed, the numerous biotic and abiotic variables that influence crop health are rarely independent of one another. Such complexities point to the need for more integrative, multidisciplinary research on agricultural systems that will provide a deeper understanding of the conditions under which microbial biocontrol agents might be most productively applied.

The goals of an IPM program are simple: minimize the economic and environmental costs of controlling plant pests and achieve sustainable agricultural production. All disease management strategies have associated costs. Growers need to carefully assess the potential costs and benefits of different disease management strategies. Conventional growers may have more options available to them in terms of chemical alternatives, but economic pressures to limit rotations or reduce tillage may promote more serious disease problems. In contrast, certified organic farmers are prevented from using most pesticides, including those commonly used as seed treatments, but longer and more diverse rotations may limit disease problems. In both cases though, thorough disease assessments are needed to determine the amount of disease pressure present and the causal agents. If the severity of a particular disease problem justifies management action beyond the first two tiers of the IPM model described above, then on-site testing of biocontrol products can generally be recommended. Because research has shown that the efficacy of microbial biocontrols can vary somewhat from site to site and year to year, trials should include the use of side-by-side comparisons with untreated controls and adequate replication across the farm over multiple growing seasons.

There is a growing demand for sound, biologically-based pest management practices. Recent surveys of both conventional and organic growers indicate an interest in using biocontrol products, suggesting that the market potential of biocontrol products will increase in coming years. Applications of diverse biological control strategies have been successful in the greenhouse industry (where environmental design and control is greatest) and continue to increase.

If the bio-control agent is Good enough to make the result in field as in lab assay with no harmful effect it would be welcomed by all. I also worked on Entomopathogenic nematodes as biocontrol agents in labs it gave fruitful results and in fields it was okay okay. so there is potential need for research to find the indigenous strains of bio-control agent which are really good and helpful.

Regarding indirect Not targeted effect, it would be there in some biocontrol agents. The bio-control activity is always going in nature and we just discover it and exploit it in our own use. but if the control is species specific then its okay. Broadly all biocontrol agent is non- specific and also harm the non-targeted organism. so to say these are lots of product in market but non of them is fully researched so I will say there is sufficient and sustainable use of biocontrol agent is necessary which is fully approved by scientific community and cant be used alone it should be incorporated in Integrated Pest management.

I try to give a very short, general and simple answer to a very complex question. BCA's are living organisms with an evolving genome, sometimes little known bio-cycles and metabolisms and a multitude of ecological interactions. No lab experiment or literature search will ever give you a complete overview of the possible behavior of the BCA in a new environment. Valuable risk assessments were developed only for a limited number of well described BCA's for a number of target organisms, crop systems and geographic areas. Even then, BCA's can behave unpredictable and result in negative impact on non-target organisms. I still think that biological control of pathogens can be a very useful and environmental friendly control strategy. However, a serious risk assessment has to be conducted before every new BCA's before used in the field to minimize possible negative side effects.

BCAs have been used for managing many plant pathogens. but they are effective against some of the pathogens at certain environmental conditions.

Good discussion. I will site an example. Application of Gambusia affinis which was used to control mosquito larvae and it found very effective too. on the other hand, we can see introduction of an exotic fish to the aquatic system. So there is chance of exotic invasion on the later on. Biological control will always have minimum side effect. Here lies the plus point.

Dear Udari and others interested in this discussion,

In my opinion, field release of biological control agents should not be done without a risk assessment (and indeed this is usually done), and in that case it is in most cases more sustainable and specific than application of pesticides. The specificity can be maximized by using specialist natural enemies rather than generalists, which minimizes the risk of non-target effects. Indeed such specificity is one of the major assets of biological control, next to the minimization of pesticide-load in the environment, and the lower likelihood of the evolution of resistance (as is very common with the use of pesticides). On the other hand, one of the main reasons why pesticides are still commonly used in favour of biological control, is the time lag with biological control: with pesticides, the organisms drop dead almost immediately (if well applied), whereas with biological control, a farmer does not actually see, for example, pest insects dropping dead immediately, but only after the enemy has established and attained the required population size to suppress or eliminate the pest. Weighing the cons and pros, I feel that biological control, supported by a good risk assessment and scientific study on optimal application, is by far preferable over pesticides in most cases. Examples are known where the use of pesticides is actually aggravating the problem, e.g. in rice culture. On the other hand, one of the best examples of succesful use of biological control is that of the cassava mealybug in Africa, which has been at least suppressed to sub-pest status by employing parasitoid wasps, eg. Epidinocarsis lopezi. But, the example of the release of the Asian multicoloured ladybird beetle, Harmonia axyridis, in the USA and Europe to control aphid pests, after which the ladybird itself has reached pest status on both continents, illustrates that appropriate research and risk assessment is crucial. I would stongly advocate the allocation of more resources for research on the development of such risk assessment protocols, and optimization of the use of the biocontrol agents, for a sustainable pest control.

Biocontrol is one such an buffering type of mechanism where in two living things react to each other i.e. both should have congenial environment for existence, later for action. If the micro climate is available, then works out well or otherwise not so

In future biocontrol agents has got lots of potential to research upon which are specific and can give better results in field.

Dear all

It is indeed a very interesting discussion. In Egypt, the use of BCAs has received lately notable attention especially in some cash crops that mainly cultivated to be then exported to Europe and rich gulf countries. Fortunately, I was involved in some projects to control aphid and sucking insects in pepper greenhouses in which we were inundativly releasing some BACs as lacewing larvae, Coccinellid adults and larvae in addition to some aphid parasitoids. Indeed, the outcome from greenhouses that were controlled by BACs was clearly efficient on the long ran compared with those controlled by conventional manners. However, in this famous private company (SEKEM group), I have to say that they are using biodynamic farming system as no single inorganic or mineral element is utilized in growing crops which subsequently helps a lot to yield more benefits from applying biological control technique in controlling greenhouse pests.

In my opinion, biological control alone does not promise effective control. It should be part of integrated pest management, whereby source reduction & environment management and chemical control is also included. As chemical control may affect non-target insects it may be replaced with botanically based larvicide.

As for indirect ecological effects of biological agents, I would recommend you to survey the test area first to find out what are the other non-target insects/organisms that co-habits with your targeted vector. Biological agents are not known to cause non-target effects. However, a planned release of biological control agents (interval time) can reduce the non-target effects, if any.

Dear Dr. Wanigasekara,

During 45 years searching new methods of control, particularly of  Mediterranean scale insects, I have obtained some good results in scale-insect control using parasitoids only. Condition of success is to obtain hymenopteran parasitoids which live in the countries of origin of  pests. Then laboratory or insectarium studies are needed for stating that one candidate parasitoid, received from the country of origin of the pest, can add its beneficial effect to beneficial effects of the entomophagous parasitoids and predators native from Mediterranea area. If yes, a new species of hymenoptera can be included in the biocenosis of hte pest, by pointing out mean of cheap mass culture and doses to relaese in the field.  Cases can occur where two specific imported hymenopteran parasitoids can better control the pest than one. For instance, one  of them killing young instar nymphs , and another old ones or adults of the pest. Sometimes, when complete biological control is impossible with introduced and native beneficial insects, it needs to use one chemical for completing control at some month of the year (proicess of integrated control).

Dear Collègues, My field of Research in biological control of scale insects was a very good success during past years (1979-1995) for olive growers of south France. When the black scale, Saissetia oleae (Olivier, 1791), became the main pest of olive orchards whereas before, main pest was the olive fly. Many olive growers used biological control by supplementing their orchards by cultured two species of Metaphycus (Encyrtidae). Stocks of which was furnished by my lab (French National Research Institute for Agriculture), culturing being made inside farmer's properties. During many years before to propose the two species of Metaphycus, I was testing risk many other species of chaldid-flies (Encyrtidae, Aphelinidae), to destroy other species of scale-insects (cultivated in my lab) in the wild environment (garrigues, macchia) of olive orchards. Now main pest of olive trees in France is one phytoplama imported through Prouilles. This kind of success of biological control would be impossible.

Surely the use of biological control agents (BCAs) must be the step practiced after risk assessments. However, I think the risk is much lower than that imposed by chemicals. I am surprised that the chemicals approved after risk assessment tests are associated with a range of malignant impacts such as blood cancer (no matter, where the chemical had brought from, a well-developed industrial Country in Europe, or a newly developed Countries in Asia). Different BCAs need different rates of risk considerations. To me, a BCA application is more rational and ecologically safer. BCA must be applied for the mid-long term strategies in an integrated disease/pest management program where all the components are rationally applied. It needs more considerations like that in chess. Finally, I am not against chemicals but these should be produced and applied under highly controlled conditions.

Biological control has not a chance if pesticides are in the front line.

Maybe correct now, however, Scientists must do their best in order to decrease the reliance on the chemicals, reduce environmental and health risks, and improve the application techniques and bioformulations to improve the yield of biological control. Currently, most of Scientists in the developed Countries have been severely attracted to the chemicals because of the huge Industries and Companies that support the related Research. Biologicals (biopesticides and biofertilizers) have just recently attracted some attention! but have led to considerable accomplishments. There are now known Companies in Europe and North America that produce effective bioproducts.