The answer is there already integrated pest management (IPM).

one of the Integrated pest management conceps is use the chemical insecticide as the last desicion or applied it if  the pest population is high,(base on its economic treshold)

Dear Fungai,

This is a very relevant question, where you implement a couple of assumptions, such as the low effectivity of Biocontrol. This assumption, in particular, is not necessarily true at all in many cases. Look, for exaple, at the succesful biocontrol of the Cassava mealy bug in Africa by the parasitoid wasp Epidinocarsis lopezi (if the genus hasn't changed in the meanwhile ;-). This wasp is now (2014-2015) again employed to combat the same pest in Asia. What IS one of the most problematic aspects of biological control, in my view, is a psychological one: farmers don't actually see the pest insects die on the spot; it takes more time than spraying chemicals, that is, if the insects have not become resistant against the chemicals! Potentially, biological control is not only much more sustainable, but also highly effective, and what is needed is a lot of investment in three things: research on maximizing the performance of the biologicalcontrol agent, research on mass culturing and selective breeding, and an investment in involvement of the farmers themselves in applying this technique. Fortunately, all these issues are addressed at present, and indeed, especially in the context of an IPM approach, it is now recognized that biological control is often a valuable component. On the other hand, it is becoming more and more clear that a pure "insecticide spraying approach" is less and less desirable; not only does it lose its effectiveness because of the development of resistance, it also causes health issues (I know of an example where people actually begin to prefer to buy fruits in the market that have been attacked by pest insects as evidenced by the damage of the fruit, over completely "clean", spotless ones, which might carry a large residue of chemicals and may therefore impair health. Apart from this, mere spraying may actually CAUSE pest problems, because the whole community of potential bio-control agents is also killed by the spraying.

Dear Fungai,

I´d say the answer is IPM in ten years from now.

By that time farmers will be used to a combination of chemicals and biocontrol, the public will not accept aggressive agro chemicals anymore and - hopefully - the evidence that this approach works best will be overwhelming.

I doubt we will go back to the chemicals only approach from 20 years ago, simply because we know right now how much damage it can do. However, a series of anecdotal reports about the effectiveness of biocontrol agent against disease x is not helping and much more research in that area has to be conducted from independent research groups to fully understand the complex biological mechanisms behind biocontrol...

an IPM program based on Biological control or natural control??? in fact there are many answers but I think it depends on our attitude. both biological and chemical control are two manipulative program handling by man in nature and agricultural systems. I dont think so that even IPM can solve our problems till we manipulate the world :(

Promote ecological engineering. This will enhance the presence of beneficial organisms in the farm

Dear Fungai:

agricultural science is the less reproducible of sciences, given the huge diversity of situations and environments in which crops are produced, worldwide. So, you are asking for a general, global rule that works under any circumstances, a target that may be very difficult to achieve indeed. In general, chemicals induce a structural change in the ecosystem, including the massive killing of other beneficial organisms, and may induce a dependency. In fact, by losing natural antagonists (i.e. predators or parasitoids) farmers will see an increase, after a given delay, of the original pest density, with a result opposite to what they expected. And then, they may be induced to treat again the crop, worsening the situation. On the other hand, biocontrol agents may be difficult to find, or the pest may be free of effective antagonists, i.e. when it is a new colonizer or due to a climate change. In this situation an IPM approach may help.

In any case, it is the crop that acts as a driver, since it provides the pest the food that sustains its population growth. So, also the crops' traits have to be known, in particular as concerns resistance and agronomic technologies for pest avoidancce (i.e. advanced sowing, rotations, use of mixed varieties, use of traps or pheromones  etc.). As others have stated, research is needed to get some rational perspective about the preferred strategy.

The Green Revolution has been mainly promoted by the introduction of synthetic fertilizers and genotypes breeding. Pesticides followed, but their costs (economic but also environmental and health costs) have to be known. Also, pesticides may show different efficacies, depending on their use, on other local situations (i.e. environment, climate) and on the pest susceptibility ( a major concern is the insurgence of resistant pest genotypes that may be selected by repeated spraying in a few generations).

In conclusion, a rational approach is needed, based on field research data and tests, to identify the most appropriate pest management strategy and its direct and indirect consequences. The management technology, in any case, has to be tailored on the peculiarities of the local problem to solve, since no general rule exists.

Apart from all of your interesting arguments, there is one strong reason for slow acceptation of Biocontrol in practice: there is and continues to exist a huge gap between science and practice. What Science knows and writes is not necessarily reaching the farmers. Our language is often too far from that of the farmers, they are not normally the most school educated, and pharmaceutical industry is far more experienced in marketing and lobbying.  

As Joop Van Lenteren points out in his conclusions : During the past 120 years, a large number of natural enemies has been collected and evaluated for use in augmentative biological control programmes. Particularly during the last 30 years many efficient species have been identified and currently at least 230 species are commercially available globally. Today, the commercial biological control industry is well organized, has developed mass production, shipment and release methods as well as adequate guidance for farmers. The industry has intensively collaborated with the public research sector in design of quality control programmes, which are applied during natural enemy production and shipment. The industry also cooperated in preparing environmental risk assessment methods for biological control agents. In several areas of agriculture augmentative biological control has obtained considerable successes and is now a reliable and appreciated element of IPM programmes. Despite all this progress, augmentative biological control is applied on a frustratingly small acreage. Different reasons explain the slow uptake. The pesticide industry considers biological control as cumbersome and of restricted use, most farmers have become pesticide addicted during the past 60 years, governmental institutions do not enforce or stimulate non-chemical pest control, and many regulations concerning the collection and application of biolog- ical control agents delay or even prohibit their use. Recent developments may, however, lead to a promising future for augmentative biological control.  J. C. van Lenteren 2011, Plenty of natural enemies, frustrating lack of uptake In addition to the ever ongoing development of resistance of pests to pesticides resulting in a need for alternative control methods, requirements of residue free food by supermarkets and consumers, prioritizing use of IPM by governmental institutions like the European Union and termination of pesticides subsidies, will all result in better possibilities for biological control. After 60 years of chemical control, we are entering the ecology-based pest management era!

In our super accelerated times most people lose the benefits of patience. Biocontrol and IPM techniques are often not strikingly "visible", though at the long run effective, more efficient and much less expensive, when beneficials can establish in the ecosystems. 

Having worked during 35 years in the study and promotion of biocontrol understanding, development and application, 10 years seem still a short time to give sustainability the needed chance.

I would like to thank you all for your informative responses. The general consensus among discussants is that IPM is the way to go. However in a situation where one has to choose, biocontrol seems the option by most of the discussants. Indeed.

 Dear Fungai:

    In the view of many people, without the help of pesticide, we can't maintain garin production to survive. I don't think so. I think we can contol these pests with the help of other control mearsures (physical mearsures，biological mearsures and agricultural measures) instead of using chemical pesticides.

    I have spent three years to do field experiments to help a agricultural company to produce organic wolfberry (Lycium barbarum L.) instead of using pestide. We can contol pests effectively, sometimes the contorl effect is better than chemical pesticide.  What we do is just spraying biopesticide and taking physical measures. However, you should know the population dynamic of these pests and know that which stage is the most weak to control and which measure is the best. For a farmer, even some technician, it is very difficult to acquire these skills. 

    I think it is possible to control pests without sparying chemical pesticides. what we  most need is to spread plant protection knowledge and set some example fields.

This question will never loose its interest.

Massive pesticide use has begun in the 1940ies with DDT, and we can put several questions: how did mankind find food to feed on before? Or: how was it that crops were not totally destroyed without pesticide help? You guess it: nature has its own techniques to limit mass outbreaks of pests of all sorts. When we speak about biocontrol we just use part of a copy-paste game ... we try to copy Nature's own methods. They have functioned longer than our attempt to do agriculture, so they are tested!

With our competitive thinking, we look for "gold medal winners" in the "olympic Laboratory games" where we test candidate species for efficient biocontrol to be quality controlled and mass reared for releases to end up with the pests (pretending to eradicate them). Why can't we understand that we are interfering in complex systems where the existence of a (potential) pest is the guaranty for the existence of all its natural enemies? There is nearly never only one species doing the job alone. Insects undergo (everybody knows it) several stages like egg, larvae, some also pupae, and adult. each development stage has its own natural enemies. If we sum them up for Helicoverpa armigera, the 2000 eggs of one female are controlled by at least 12 natural enemy species at different degrees to allow in the end (if no pesticides are used) in the next generation 2 females and one male to get through. Our attempt to hinder larvae to develop (as they are the harmful stages), makes us choose and use Trichogramma ssp. hoping they will do the job, alone. Or, if we understand the system, we hope (!) that the absence of pesticides will allow the other natural enemies existing in nature to help control the later stages. Everything is density dependent. If we controlled 100% of the eggs, there were no resources for the larval parasites, the pupa consumers and the bats and birds that feed on adults. They would get out of the system. 

The better we understand the system (agricultural productive system) with its obligatory participants, and respective dynamics, the better we can manage it. It needs lots of knowledge and that must be shared with the farmers to get their cooperation. The triggers for all population dynamics are the microclimate factors, which favour or inhibit the development of the host plant, the pests and natural enemies, fungus diseases etc. And they are never the same in successive years, unless you work in greenhouses. Based on their register, we can develop reliable forecast systems, and once their are established, they function! If we only look for easy and superficial solutions, they must fail and discredit biocontrol. 

I've worked for about 30 years in this passioning detective job, and discovered that a lifetime is too short to understand it all. But is that reason enough to destroy these filigrane natural interactions with pesticides because we are in a hurry? Can we really correct Nature?

Can you send me this article? please