[compostteas] Interactive biocontrol mechanisms for plant disease control

Steve Diver steved at ncat.org
Sat Aug 20 22:59:50 EDT 2005

The biological control mechanisms (i.e., competition,
induced plant resistance) that prevent infection
from plant pathogenic organisms (i.e., pythium,
fusarium, rhizoctonia) for composts, compost
teas, microbial inoculants, crop rotations,
and soil organic matter amendments are similar.

The following quote from a new online journal 
article is helpful.  It puts biocontrol mechanisms
into perspective. Multiple interactions occur
simultaneously; they are not isolated and

"Biocontrol agents exert disease suppression by
different modes of action including competition,
direct parasitism, antibiosis and induction of
plant resistance mechanism (Whipps, 2001). None
of the mechanisms are necessarily mutually
exclusive and frequently several modes of action
are exhibited by a single biocontrol agent."

"The mechanism by which P. fluorescens exerts its
antagonism against Pythium sp. has been extensively
studied and appears to involve the production of
a variety of antibiotic compounds (Howell and
Stipanovic, 1980; Sharifi-Tehrani et al., 1998;
Thrane et al., 2000), competition (Mohamed and
Caunter, 1995; Ellis et al., 1999) and induced
resistance (Benhamou et al., 1996; Ramamoorthy
et al., 2002a)."

Selected reference citation:

Whipps, J.M. (2001) "Microbial interactions and
biocontrol in the rhizosphere" J. Exp. Bot. 52: 487-511


Antagonist Microorganisms with the Ability to Control
Pythium Damping-off of Tomato Seeds in Rockwool

Publisher: Springer Science+Business Media B.V.,
Formerly Kluwer Academic Publishers B.V.


Issue:  Volume 50, Number 5
Date:  October 2005
Pages: 771 - 786

Valerie Gravel, Carole Martinez, Hani Antoun and
Russell J. Tweddell

Université Laval, Québec, Canada


A total of 237 microorganisms were isolated from five
different greenhouse tomato growing media. Of those,
40 microorganisms reduced the in vitro mycelial growth
of both Pythium aphanidermatum and Pythium ultimum.
The ability of these microorganisms to control
damping-off was then tested in rockwool. As a result,
Pseudomonas corrugata strains 1 and 3, Pseudomonas
fluorescens subgroup F and G strains 1, 2, 3, 4 and
5, Pseudomonas marginalis, Pseudomonas putida subgroup
B strain 1, Pseudomonas syringae strain 1 and
Pseudomonas viridiflava significantly reduced
damping-off caused by P. ultimum or P. aphanidermatum.
Pseudomonas marginalis was the only microorganism
that significantly reduced damping-off caused
by both pathogens.


Steve Diver

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