Your question is interesting and relevant. To answer it appropriately, one should be aware of the main objective and the system (e.g. eradication of a pest by a predator in apple orchards in Canada) involved. In that example, winter survival is a big concern in several regions of Canada.

There are a number of issues to consider. When dealing with biological control, narrow host range, high searching efficiency, and their ability to adapt to the regions where they are introduced. Solitary parasitoids have been found to be quite good.

This is not the question in the field of my specialty, but each of the six characters seems to be important. Thus, a good candidate would be the one that has as many characters as possible among those six.

To further add to my answer and go forward, let me ask you a question: what is your target system ?

Please answer as follows: Insect or disease/plant/region  (natural enemy)

For exampe: Apple sawfly/apple tree/Eastern Canada     (Lathrolestes ensator- Ichneumonidae)

All the best

Dear Masoud:

The selection of the most appropriate type of biological control will depends on several factors for this to be effective.

1. First you have to identify the category of natural enemies of insect pests : predators, parasitoids, and pathogens because the mode of action of each is different.

2. Second you have to identify which is the target species to be controlled, if is an introduced or native species.

3. If is a native species, you need to identify which are the inadequate agronomic practices that are causing population increases of the pest (eg. overuse of insecticides, destruction of beneficial insects, generalized use of herbicides, destruction of alternate host plants, susceptible plant varieties).

4.The biology of the pest must be known and their natural enemies well identified.

5. You must establish an integrated pest management involving different control strategies (cultural, biological, genetic, chemical, ethological, physical) to be austosostenible in time and to avoid creating ecological imbalances.

6. The  environmental and climatic factors affecting the biology and population dinamic of the insect pest must be well known.

With this basic information, then  you should focus on the selection of  the most efficient  host specific natural enemy taking in consideration all the criteria you mention.

Regards,

Luis Miguel

Dear Masoud,

In natural ecosystem the balance between the pest and the benefit organism is found. As a result of human intervention in the ecosystem the unbalance occur. For this we begin to ask about the most biological method for control and our answers must make it clear that the best comes after the tests and not before. The reasons for this are more to  write as the pest type, the habitat, the environmental factors, the inter-specific relations,...... and so on. For all this we practice this research work to make a conclusion for what is the best.

Best regards,

aly younes

There are reports which suggests that when large number of biocontrol agents are released against pests it may lead to competition among themselves( individual biocontrol agents) for the limited prey, which may reduce the efficacy with regard to bio-control. Hence, effective and judicious release of parasitoids can also   be given due consideration

As Ruth Kahuthia Gathu  implies, parasitoids are almost always the best choice. They are very often quite specific (I earlier mentioned an exception in a previous answer about the attempted control of Piers rapae in NZ).  However, you mentioned efficient search ability, and I must admit that this could be a problem when the distribution of the host is patchy.

If the introduction of a host parasitoid is successful it will almost certainly come into balance with the host, but the question of whether that balance will be economically significant is another matter..

However,  pests are not the only things to be controlled by biological control, Dr. Warren Thomas in NZ realized that cow dung was covering up a significant percentage of pasture. So, he introduced dung beetles. If the readers decide to do this they may wish to know that the beetle species are usually size specific in their choice of the dung they will bury. Also this might not be the best idea in such places as parts of India where dried cow dung is an important domestic fuel.  As always, the control organisms must ve carefully handled to be certain that their parasitoids and diseases are not introduced with them. 

Lewis Maccarter this is true to a number of parasitoids.  in 2002 I was Involved in a project on classical biological control of Plutella xylostella (DBM) in Kenya using the solitary endoparasitoid, Diadegma semiclausum from Taiwan.  Surprisingly it has been quite effective even where the DBM are scanty due to its high searching efficiency.  At times I have observed almost 100 percent parasitism.

from management point of view at least first four is necessary, lack of any one may aff

ect their efficiency

Dear Dr.Masoud,

Each of this 6 characters you mentioned above are important when choosing a biological control agent as perfect candidate. So if the candidate got almost all 6 characters would be the perfect candidate.

Best,

Tharindu

Although all the characters are important being as good biological control agent but the most important are synchrony with host  life cycle and high reproductive rate. See the synchrony of host-parasite relation, if parasite (here biological agent) have the relation with specific host it will also have the possible tactics like species specificity, ability to locate the host due to the evolutionary development during the course of time. On the other side. high reproductive rate will help them to avoid climatic fluctuations and survival over low density of host. Like in this way I think these are the most important characters of any biological control agent. 

There is also two more important point for classical biological control agent apart from the points You had mentioned they were,

All criteria except #3 and you get no efficiency !

That not mean #3 is the most important, but it will trigger good candidate.

Of course, considering non-natural ennemy.

6-Survival at low host (prey) density.

I am not neglecting the other five charachteristics, but this is an important factor, if you will have a relevant biological control agent. Otherwise, you will have a predator or a parasite, but the importance of a biologica control agent will rely on having good control when population is low, avoiding to have a huge population at any time.

All of the characters are very important while looking for a good biocontrol agent, but the most important is Synchrony with host (prey) life cycle, this point also covers the second point, NE is compatible with the life cycle of its host, definitely it will also be compatible with Climate. Point# 6 is also an important one, control on its reproduction rate according to food availability.

Dear Excellent bio control scientists, about:

Which character is more important when choosing a biological control agent as perfect candidate?

All characters of great important and we must considered: why?, Where? and When?. Best wishes.

Your mentioned each of this 6 characters are important when choosing a biological control agent as perfect candidate and third no is most important .

Each of six is important and number 2 may need to be addressed more.

I like the discussion and to me I find all the factors important because each feeds into the other for effective performance