Agriculture Reference
In-Depth Information
9.8 ROLE OF VERMICOMPOST IN PLANT DISEASE
MANAGEMENT
9.8.1 PLANT PATHOGEN CONTROL
Soils with low organic matter and microbial activity are conducive to plant
root diseases (Stone et al. 2004) and addition of organic amendments can
effectively suppress plant disease (Raguchander et al. 1998; Blok et al.
2000; Lazarovits et al. 2000). Several researchers reported the disease sup-
pressive properties of thermophilic compost (Hoitink et al. 1997; Gold-
stein 1998; Pitt et al. 1998) on a wide range of phytopathogens viz., Rhi-
zoctonia (Kuter et al. 1983), Phytopthora (Hoitink and Kuter 1986; Pitt
et al. 1998),
Plasmidiophora brassicae
and
Gaeumannomyces graminis
(Pitt et al. 1998) and Fusarium (Kannangowa et al. 2000; Cotxarrera et al.
2002). Microbial antagonism might be one of the possible reasons for dis-
ease suppression as organic amendments enhances the microbial popula-
tion and diversity. Traditional thermophilic composts promote only select-
ed microbes while non-thermophilic vermicomposts are rich sources of
microbial diversity and activity and harbour a wide variety of antagonistic
bacteria thus acts as effective biocontrol agents aiding in suppression of
diseases caused by soil-borne phytopathogenic fungi (Chaoui et al. 2002;
Scheuerell et al. 2005; Singh et al. 2008).
Earthworm feeding reduces the survival of plant pathogens such as
Fusarium
sp. and
Verticillium dahliae
(Yeates 1981; Moody et al. 1996)
and increases the densities of antagonistic fl uorescent pseudomonads
and fi lamentous actinomycetes while population densities of
Bacilli
and
Trichoderma
spp. remains unaltered (Elmer 2009). Earthworm activi-
ties reduce root diseases of cereals caused by
Rhizoctonia
(Doube et al.
1994). It has been proved that earthworms decreased the incidence of
fi eld diseases of clover, grains, and grapes incited by
Rhizoctonia
spp.
(Stephens et al. 1994a; Stephens and Davoren 1997) and
Gaeumanno-
myces
spp. (Clapperton et al. 2001). Earthworms
Aporrectodea trapezoi-
des
and
Aporrectodea rosea
act as vectors of
Pseudomonas corrugata
214OR, a biocontrol agent for wheat take-all caused by
G. graminis
var.
tritd
(Doube et al. 1994). Greenhouse studies on augmentation of patho-
