Agriculture Reference
In-Depth Information
Obradovic and co-workers (Obradovic
et al.,
2004, 2005) determined that application of
formulated phages resulted in reduced disease and increased yield.
The issue of sunlight avoidance was illustrated when Flaherty
et al.
(2000) effectively
controlled the tomato bacterial spot pathogen in fi eld experiments by applying phages in
the early morning hours prior to sunrise and achieved no control if phages were applied
during the day (unpublished results). Iriarte
et al.
(2007) showed that phages persist bet-
ter if applied in the evening rather than in the morning (Figures 13.1 and 13.3a). Balogh
et al.
(2003) more defi nitively demonstrated that sunlight avoidance during phage appli-
cation led to increased control by showing that bacteriophages applied to tomato plants in
the fi eld in the evening signifi cantly reduced disease compared to morning applications,
resulting in 26.9% and 13.1% disease reduction, respectively (Figure 13.3b).
A unique advantage of bacteriophages in comparison with chemical pesticides is the
ability to increase their numbers in the target environment by multiplying on a bacte-
rial host. This ability can be exploited if phages are applied into an environment where
a phage-sensitive bacterium is present, or alternatively, they are delivered together with
the host. In an environment where high host populations are present and conditions are
favorable, phages persist much better than without the host (Balogh, 2006) (Figure 13.4).
7
6
5
4
3
2
1
0
0
4
8
12
16
(a)
Time after application (h)
A
70
B
60
C
50
40
30
20
10
m
e
(b)
0
Figure 13.3
Evening phage application results in increased residual activity and better disease control.
(a) Effect of application time on phage residual activity in the fi eld. Phage suspension was applied to fi eld
tomatoes in the morning at 6:00 (solid diamonds) or in the evening at 19:00 (open triangles). Vertical
dotted lines indicate the end of the predicted residual activity based on 10
4
PFU cm
−2
threshold. (b) Effect
of application time on phage disease control effi cacy. Phage mixture was applied twice-weekly through-
out the tomato growing season in the evening or in the morning. Area under the disease progress curve
(AUDPC) values indicate the overall disease progress. UTC: untreated control.
