Agriculture Reference
In-Depth Information
decreased in a dose-dependent manner on the application of AgNPs. Nano-silver
treatments were also found to be effective against bacterial growth in vase solution
and at cut stem ends, thus extending the vase life of
Gerbera jamesonii
cv. Ruikou
flowers (Solgi et al.
2009
; Liu et al.
2009
).
Nano-silver-silica composite obtained by mixing a silver salt with silicate and
a water-soluble polymer followed by exposing the mixture to radioactive rays,is
reported to have excellent antimicrobial effects even at its low concentrations (Oh
et al.
2006
). Such nano-sized silver-silica composite could be successfully used
against plant pathogens. It was reported that plant pathogenic fungi such as
Phy-
tophthora spp
.,
Rhizoctonia
spp.
,
Colletotrichum spp
.,
Botrytis spp
.,
Magnaporthe
spp
. and
Pythium spp
. could be successfully controlled using nano-silver-silica
composite (Park et al.
2006
). Various experimental results have shown that this
nanocomposite at a concentration lower than 3.0 ppm is effective enough to control
various plant diseases caused by the above said plant pathogenic fungi. On ab-
sorbing such nano-silver silica by fungal cells, AgNPs increase disinfecting activity
whereas silica nanoparticles provide physical barrier to pathogenic fungi, thus in-
ducing increased resistance to diseases by preventing the recurrence of diseases for
extended periods after disinfection of phytopathogens. Nanocomposition was also
found to be effective against phytopathogenic bacteria at a concentration higher than
10 ppm. Hence, it is necessary to optimize the minimal effective concentrations of
nanoformulations, that is, effective enough to fight against each phytopathogen.
The best thing regarding the use of nano-silver-silica is that it could provide long-
term control of microorganisms very selectively depending upon its concentration
with single application and is safe for growers also since it does not cause chemical
injuries and is non-toxic to humans. Such nanoparticle formulations are effective
against phytopathogens that are less sensitive to antibiotics due to their poor pen-
etration into microbial cells.
3.2 Nano-Silica
There were reports regarding the use of amorphous nanosilica as a nanobiopesti-
cide. Use of nanosilica opens up novel research area for the biological control of
various plant pests. Nanosilica controls insect pests by their absorption on cuticular
lipids by physiosorption. They do not cause alterations on genetic make-up of insect
pests and hence the process is purely physical (Barik et al.
2008
; Mewis and Ulrichs
2001
).
3.3 Titanium Dioxide Nanoparticles (TiO
2
)
Titanium dioxide (TiO
2
) is a non-toxic white pigment widely used in the manu-
facture of paints, paper, ink, cosmetics, ceramics, leather, etc., and is a very strong
