Agriculture Reference
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polyhedrosis virus), respectively. After 7 days of exposure, 95 and 86 % mortality
were observed with hydrophilic and hydrophobic formulations of Ag
nanoformulations, and nearly 70 % of the insects were killed when the rice was
treated with lipophilic formulations of Ag nanoparticles (Goswami et al. 2010 ). The
antimicrobial activity of titanium dioxide has been recognized, and its application
can suppress both bacterial and fungal crop pathogens. The use of nanoformulations
of TiO 2 -Zn could result in significant reduction of bacterial spot severity in
tomatoes in both greenhouse and field trials (Paret et al. 2013 ). Copper
nanoformulation has been also reported to suppress the growth of bacterial blight
on pomegranate at concentrations 10,000-fold lower than that usually
recommended for copper oxychloride (Mondal and Mani 2012 ). Formulations
with calcium carbonate nanoparticles showed prolonged activity of validamycin,
which can be explained by the sustained release of the antimicrobial over 14 days
for control of R. solani (Quian et al. 2011 ).
Silver nanoparticles are the most studied nanostructures for inhibition of plant
pathogens. The antifungal effect of double-encapsulated Ag nanoparticle solution
against rose powdery mildew caused by Sphaerotheca pannosa var. rosae was
investigated. The nanoparticle solution was diluted up to 10 ppm and sprayed at a
large area infected by S. pannosa var. rosae . Two days after the spray, more than
95 % of rose powdery mildew faded out and did not return for a week (Kim
et al. 2008 ). Min et al. ( 2009 ) studied the use of Ag nanoparticles as an alternative
to pesticides for the control of sclerotia-forming phytopathogenic fungi. Ag
nanoparticles, which have high surface area and high fraction of surface atoms,
showed improved antimicrobial effect when compared to the bulk silver. A micro-
scopic observation revealed that hyphae exposed to Ag nanoparticles were severely
damaged, resulting in the separation of layers of hyphal wall and collapse of
hyphae. The antifungal activity of Ag nanoparticles on Colletotrichum
gloeosporioides , which causes anthracnose in a wide variety of fruits, was inves-
tigated by Aguilar-MĀ“ndez et al. ( 2010 ). A significant growth delay of
C. gloeosporioides in the presence of Ag nanoparticles was noticed. The in vitro
activity of Ag nanoparticles against 18 phytopathogenic fungi was recently dem-
onstrated (Kim et al. 2012 ). Therefore, Ag nanoparticles could be an alternative
fungicide to manage some plant diseases.
Efforts for the preparation of bionanoformulations of metallic nanoparticles with
antifungal activity are gaining interest. The synthesis of silver nanoparticles with
well-defined morphology and stability over several months can be achieved by
several fungi, including F. oxysporum , Trichoderma asperellum , Trichoderma
viride , and a number of Aspergillus spp. (Kashyap et al. 2013 ). However, their
potential as antimicrobial agents to combat plant pathogens in the field needs to be
further investigated.
In addition, metallic nanoparticles can be used as nanocarriers to antimicrobial
agents. Nickel nanoparticles coated with a monolayer polyacrylic acid nanofilm
were used to immobilize the antimicrobial peptide LL-37. This nanocomposite was
effective to kill E. coli (Chen et al. 2009 ). Iron oxide magnetic nanoparticles coated
with polymers, in particular with biopolymers such as polysaccharides, can be
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