Agriculture Reference
In-Depth Information
Table 8.3.
Effect of
Alternaria
conidia concentration and spray volume on
Sphenoclea zeylanica
biomass and density two weeks after application in field
experiments
Conidia concentration
Spray volume
Biomass
Density
(conidia mL
1
)
(mL0.25 m
2
)
(g 0.25 m
2
)
(number 0.25 m
2
)
Experiment 1
0
50
11.2
201.8
7.0
10
5
50
0.2
16.3
1.8
10
6
50
0.04
5.3
Experiment 2
0
50
17.1
81.5
8.0
10
3
50
13.7
93.0
3.0
10
4
50
8.0
79.5
2.6
10
5
50
0.2
4.3
Experiment 3
0
0
17.6
145.0
1.6
10
6
12.5
3.0
40.7
1.6
10
6
25
0.8
9.3
1.6
10
6
50
0.2
1.3
Experiment 4
0
0
28.2
169.3
4.8
10
5
12.5
10.5
89.7
4.8
10
5
50
2.1
33.3
Source:
Adapted from Mabbayad & Watson (1995).
crop species. Competition from
C. album
reduced maize biomass 20% when
A.
caulina
spores were not applied, but the weed had no effect on maize growth
when sprayed with the fungus. Competition from
C. album
reduced sugarbeet
biomass 80% in unsprayed plots, but reduced it only 20% to 60% when the
mycoherbicide was applied.
Similarly, in experiments conducted by Paul & Ayres (1987), competition
from
Senecio vulgaris
against lettuce was diminished or eliminated by applica-
tion of
Puccinia lagenophorae
spores
.
In the absence of the pathogen, lettuce
fresh weight was reduced 50% to 97% by competition from
S. vulgaris
sown at
densities of 250 to 65000 seeds m
2
. When
S. vulgaris
was infected by the
fungus, however, the weed had no effect on lettuce yield until its sowing
density was
4000 seeds m
2
. Even in treatments containing the highest
S.
vulgaris
densities, lettuce yield in plots sprayed with
Puccinia lagenophorae
spores was higher than in unsprayed plots. Infection by
P. lagenophorae
had
little effect on the density of
S. vulgaris
growing with lettuce, but reduced the
weed's biomass by an average of 16%.
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