Agriculture Reference
In-Depth Information
90
a
80
ab
b
b
70
b
60
50
40
30
20
10
0
Food
waste 5.0
t/ha
Food
waste 10
t/ha
Food
waste 5.0
t/ha
Food
waste 10
t/ha
Inorganic
fertilizer
FIGURE 18.6
Verticillium wilt damage to strawberries grown in field soils treated with vermicomposts
produced from food waste and paper waste vermicomposts. Columns with the same letter or letters are not
significantly different at
p
≤ .05.
Orlikowski (1999) described sporulation reduction of the pathogen
Phytophthora cryptogea
after
treatment with vermicomposts. Studies by Nakasone et al. (1999) showed that aqueous extracts
of vermicomposts inhibited the mycelial growth of
Baptista cinerea
,
Sclerotinia
sclerotiorum
,
Sclerotium rolfsii
,
Rhizocronia solani,
and
Fusarium oxysporum
.
In greenhouse experiments in the Soil Ecology Laboratory at OSU, there was significant
suppression of
Pythium
and
Rhizoctonia
resulting from substituting low rates (10 to 30%) of
vermicompost into horticultural bedding mixtures (Chaoui et al. 2002). Suppression of diseases of
field crops was achieved with low application rates of vermicomposts. The diseases suppressed in
the field were
Verticillium
wilt on strawberries (Figure 18.6) and
Phomopsis
and powdery mildew
(
Sphaerotheca fulginae
) on grapes.
Two mechanisms of pathogen suppression have been described: one is based on microbial
competition, antibiosis, hyperparasitism, and possibly systemic plant resistance (Hoitink and
Grebus 1997). The second method of suppression of diseases such as
Rhizoctonia
has only a
narrow range of microorganisms facilitating the suppression, termed
specific suppression
(Hoitink et al. 1997). It seems likely that these two mechanisms of suppression also apply to
vermicomposts, but probably general suppression is much more common for vermicomposts
because vermicomposting increases the biodiversity of microorganisms greatly whether patho-
genic or beneficial.
I
NSECT
P
ESTS
There are some reports in the literature demonstrating that field applications of various types of
organic matter and traditional thermophilic composts can suppress attacks by insect pests such as
aphids and scales (Costello and Altieri 1995; Eigenbrode and Pimentel 1998; Morales et al. 2001;
Phelan et al. 1996; Sudhakar et al. 1998; Yardim and Edwards 1999). There have been scattered
reports of the suppression of insect pest attacks on plants by vermicompost amendments. Biradar
et al. (1998) reported a clear correlation between the amounts of vermicomposts in the medium in
which
Leucaena leucocephala
was grown and the degree of infestation by the psyllid
Heteropsylla
cubana
. Rao et al. (2001) reported lower overall pest densities of ground nut leaf miner (
Aproaerema
modicella
) in plots treated with vermicomposts. Ramesh (2000) described decreased attacks by
sucking pests in response to vermicomposts. Rao (2002) reported very large decreases in attacks
by the jassid (
Empoasca verri
) and the aphid (
Aphis craccivora
) and changed predator populations
