Alan,

All my experience shows that evaluation of biopesiticides in soil cannot be done in one trial  - the effect of every-season application is growing year by year, and will reach plateau   in 3-4 years. 

Alex

Effectiveness is studied differently depending on the aim of the study. It is not clear if you would be interested in studying the mode of action and survival of a microorganism in soil in the frame of a research effort. There are several relevant to the subject papers (review papers provide a useful overview). On the contrary, for industrial development there are general efficacy requirements according to  EU Legislation based on Reg 1107/2009 and guidelines issued by EPPO ; specifically  for microbials there is the EPPO PP1/276 (1) 'Principles of efficacy evaluation for macrobial plant protection products'. In the later case, evaluations of efficacy is being carried out in pot ted plants experiments and further in contaminated, by soil borne pathogens, soils. In this case efficacy is assessed based on percentage of plants infected per plot assessed at different time intervals. There is need for multi-year and multi-location exps. 

Greetings Emilia,

Thank you for this information. This is a step in the right direction.  But what I am interested in is trying to apply the principles of epidemiology to developing criteria for evaluating microorganisms as to their effectiveness in starting an epidemic of the good microorganisms that protect the crop from the bad microorganisms.  I know that there is literature on plant pathology epidemiology so I would think that these same thought processes should be applicable to any introduced microorganisms.

Alan,

there are some basic differences between epidemiology of plant pathogens and life of biocontrol agents: 1) Plant pathogens have unlimited food resources at least at starting point of epidemics; 2) The host plant has limited genetic and physiological response diversity; 3)  in most cases the Biocontrol agent has no benefits from direct interaction with target pathogen, it is competitor or supressor of pathogen due to common food sources or antagonistic properties; 4) if the biocontrol agent can be a parasite of plant pathogen, it has benefits from high concentration of the pathogen, thus, it must co-exist in nature with non-pathogenic host to form a stable population.

Dear Alan.

I agree with Alex on the principles he mentions. My question at the moment  for me (at least) would be 'what kind of microorganisms you intent to test and their speculated/known from literature or lab experiments mode(s) of action(s). Are they hyperparasites, do they produce secondary metabolites (egpeptide antibiotics) are they sporeforming bacteria or mycorhizas? We need to have an idea in order to know. There is no common protocol to study these organsims.  On the  other hand which patrhogens do they control? Different biocontrol agents control Phytophthora (soil borne species) and others Rhizoctonia or Fusarium. This fact is due to the difference in plant pathogen epidemiology in soils.

Because interactions in soil are difficult  to be studies at situ,  potted plants experiments would give you the answers in terms of population changes under controlled conditions of both the pathogens and the biocontrol agents, the increase of their efficacy with addition of soil amendments (eg chitin) etc. In pararel you could test under such conditions possible mechanisms of SAR as introduction of microorganisms in soil might protect plants not only from soil borne pathogens but also from foliar ones etc. If you want to study deeper there is always the chance of molecular studies and advanced microscopy to observe colonisation of roots by introduced to your substrate microorganisms.

In conclusion, there is need to study the major factors that might affect their efficacy (mainly soil type, water availability, pH, nutrients, application rate in terms of biological activity  etc) and host  crop in order to study their main effect on BCAs efficacy which is much related to population dynamics and survival. In this way you will decide on the limitations of their use  but also you will start to form a possible GAP for future registration.