Quote:
But if this stuff is all about improving/maximizing soil microbes
beneficial to the root system, how does it work as a foliar spray?
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The research on this use of biocontrol organisms is very thin.
There are a few identified strains of bacteria and fungi that
will attack pathogenic foliage diseases, but whether any
particular commercial biocontrol will work for this is an
open question. Most of the existing research (that we have
reports for) was focused on biocontrols that will control bugs
that prey on foliage (spider mites, larvae, etc), not on
biocontrols for fungal or bacterial foliage disease.
I would certainly doubt that fungal mycorhizzae that
natively inhabit root systems are going to provide much
competition for foliage disease when sprayed on the foliage,
because foliage is not their natural environment. Beneficial
bacteria, like that used in Actinovate, on the other hand,
can probably adapt to more varied environments than
mycorhizzae. There may be fungal competitors (like
various trichoderma species) as well for chronic foliage
diseases that can and do survive on the leaves of plants.
There is so little peer-reviewed, reproducible research on it,
however, that I would suspect any claims that foliar spraying
of some biocontrol product is definitely going to help
the plant (unless the problem that one is trying to control is
some bug infestation, where there has been more work done).
Work on this in the scientific community continues, though.
Here is an abstract of a paper on biological control of
cucumber diseases, for example:
http://www.actahort.org/members/show...knrarnr=608_28
A good overview of plant pathogen biocontrol research:
http://www.entomology.wisc.edu/mbcn/fea303.html