(1) Background: The control of mosquitoes with essential oils is a growing demand.
(2) Methods: This study evaluated the novel larvicidal and adulticidal activity of fennel and green tea
oils and their nanostructured lipid carriers (NLC) against Culex pipiens (C. pipiens) in the laboratory,
field conditions and evaluated their effect against non-target organisms. SLN type II nanoformulations were synthesized and characterized using dynamic light scattering (DLS), zeta potential and
transmission electron microscope. (3) Results: The synthesized NLCs showed spherical shaped,
homogenous, narrow, and monomodal particle size distribution. The mortality percent (MO%)
post-treatment (PT) with 2000 ppm for 24 h with fennel oil and NLC fennel (NLC-F) reached 85%
(LC50 = 643.81 ppm) and 100% (LC50 = 251.71), whereas MO% for green tea oil and NLC green tea
(NLC-GT) were 80% (LC50 = 746.52 ppm) and 100% (LC50 = 278.63 ppm), respectively. Field trial
data showed that the larval reduction percent of fennel oil and NLC-F reached 89.8% and 97.4%,
24 h PT and the reduction percent of green tea oil and NLC-GT reached 89% and 93%, 24 h PT
with persistence reached 8 and 7 days, for NLC-F and NLC-GT, respectively. The adulticidal effects
showed that NLC-F and NLC-GT (100% mortality) were more effective than fennel and green tea
oils (90.0% and 83.33%), with 24 h PT, respectively. Moreover, their reduction of adult density after
spraying with LC95 X2 for 15 min, with fennel oil, NLC-F, and green tea oil, NLC-GT were 83.6%,
100%, 79.1%, and 100%, respectively, with persistence (>50%) lasting for three days. The predation
rate of the mosquitofish, Gambusia affinis, and the bug, Sphaerodema urinator, was not affected in
both oil and its NLC, while the predation rate of the beetle, Cybister tripunctatus increased (66% and
68.3%) by green tea oil and NLC-GT, respectively. (4) Conclusions: NLCs nanoformulation encapsulated essential oils was prepared successfully with unique properties of size, morphology, and
stability. In vitro larvicidal and adulticidal effects against C. pipiens supported with field evaluations
have been performed using essential oils and their nanoformulations. The biological evaluation of
nanoformulations manifested potential results toward both larvicidal and adulticidal compared to
the essential oils themselves, especially NLC encapsulated fennel oil which had promising larvicidal
and adulticidal activity. |
