Abstract
The present study was conducted to investigate the toxicity of Aerosil 200® (fumed silica nanoparticles) and leaf extracts of four plants,
Cinnamomum camphora
,
Matricaria chamomilla
,
Mentha arvensis
, and
Trigonella foenum-graecum
against
Thrips tabaci
(Lind.) (Thysanoptera: Thripidae) in onion fields, as well their allelopathic effects on onions; moreover, the chlorophyll, phenol, and protein contents were determined in onions. This study was performed in completely randomized plots. After a growth period of 1 month, bioassay investigations and molecular polymorphism in
T. tabaci
by RAPD-PCR were performed, and total chlorophyll, phenol, and protein concentrations were investigated in onion plants posttreatment as well. The initial reduction% of the
T. tabaci
population in onion fields after application of a high concentration of nanoparticles (Aerosil 200® (4 ml/l)) and 8000 ppm concentrations of the four plant extracts were 83.66, 81.08, 86.92, 74.49, and 91.38%, respectively, whereas their persistence effects were 73.18, 67.78, 71.46, 66.94, and 78.29%, respectively. Furthermore, the total chlorophyll contents in onions treated with the nanoparticles and four plant extracts were 1.35, 1.17, 1.09, 1.07, and 1.18 mg/g, respectively; additionally, the concentrations of phenols were 4.65, 3.15, 3.15, 2.85, and 3.70 mg/g in onions treated with
C. camphora
,
M. chamomilla
,
M. arvensis
,
T. foenum-graecum
, and Aerosil 200®, respectively. The
C. camphora
extract was the most potent, as it increased the protein content in the onion plants, while the Aerosil 200® decreased the protein content in onions. In addition, DNA-RAPD showed that the polymorphism percentages were 73, 71, and 67% when treated with high concentrations of
C. camphora
and
M. arvensis
extracts and Aerosol 200®, respectively.
T. foenum-graecum
and
M. chamomilla
extracts induced the least polymorphism (17 and 16%, respectively). Overall, this study indicated that these plant extracts as well as the nanoparticles in Aerosil 200® could be used to reduce onion infestations of
T. tabaci
in the field environment.