Study on the effect of Calcium Carbonate nanoparticles as a new strategy to control the olive fruit fly Bactrocera oleae (Rossi) in olive orchards
Author(s)
Fenjan, Saleh Falih
Date Issued
October 27, 2020
Type
Doctoral Thesis
Abstract
Nanotechnology has received significant attention in crop protection over the last
decade, in the form of nanoparticles. This research aimed at studying the effects of
application of Calcium carbonate nanoparticles CaCO3 NPs on the control of the olive fruit
fly Bactrocera oleae in the field, and on the development of all immature stages of the target
insect in the laboratory. Similarly, another formula; colloidal calcium CaCol was tested for
comparison purposes. The field experiment was carried out in an olive orchard in Viterbo
province (Lazio-Italy), yellow traps were used for pest monitoring at the onset of the
invasion, and the number of captured adults was evaluated. Infestation level was assessed
based on the number of insects detected in field-collected fruits. The orchard was divided
into three blocks that were subjected to the following treatments: (A) tap water as a control;
(B) CaCol; (C) CaCO3 NPs. Additionally, in another part of the orchard, some olive branches
were covered before the presence of the pest and were treated intensively with the abovementioned
suspensions. Thereafter, treated fruits were collected randomly and incubated to
evaluate the effect of applied materials on insect development. The monitoring results
showed that the highest peak of the fly was on October 16th and the optimal temperature for
the fly vitality was (21±5 C°). Infestation level reached the higher number of detected
individuals on 26th of September. The field tests have shown that Calcium carbonate NPs
interacts negatively with the fly emergence better than colloidal calcium, by averting the
insect development during early life stages. Laboratory bioassays were conducted in order
to ascertain the results obtained in the field. B. oleae were reared from infested olives
collected in different orchards. Afterwards, three cages were established containing an equal
number of healthy olive fruits and each cage was provided with the same number of B. oleae.
Each cage received a different treatment; CaCO3 NPs, CaCol and tap water (control)
respectively. Adult emergence per treatment was recorded after 21 days and statistically
analyzed. The results showed that insects exhibit similar lifespan, even though treated with
different materials, and no insect mortality was observed. There was a reduction in B. oleae
adult’s emergence using CaCO3 NPs, however, no significant effect was observed when
comparing Calcium carbonate suspensions with control. The ultimate objective of this
research was to study the effect of the used materials on the viability of B. oleae, female’s
productivity, as well as on the interaction between B. oleae and its bacterial endosymbiont
Summary
"Candidatus Erwinia dacicola". Several studies have documented that this bacterium plays
an important role in the B. oleae life affecting its fitness, larval development, oviposition and
mating behavior. To this end, B. oleae rearing was carried out under laboratory conditions
and three trials were performed and replicated three times. Treatments were applied by
exposing the olive fruit flies in each cage to a different component (CaCO3 NPs, CaCol and
tap water) mixed with artificial diets. Thereafter, equal numbers of treated flies were
collected from each cage at different intervals; after 1, 2 and 3 weeks of treatment, then killed
and used for Ca. E. dacicola DNA extraction. Detection and quantification of the bacterial
DNA in insect samples was carried out by qPCR targeting the 16S rRNA gene, with EdF1
and EdEn primers in order to quantify the abundance of the bacterial endosymbiont
associated with B. oleae, based on the number of cycles (Ct) values. The findings indicate
that the two formulas of Calcium carbonate incorporated into the insect diets, reduced egg
production in female flies compared to control, and that CaCO3 NPs reduced significantly
egg production than CaCol. The qPCR analyses revealed that no significant effect was
observed on the bacterial abundance in treated flies, and insect samples exposed to Calcium
carbonate NPs and colloidal calcium illustrated approximately an equal amount of bacterial
DNA compared to control throughout the trial period. Overall, our results encourage further
research on Nano-calcium carbonate, in order to use this inorganic nanomaterial for the
control of the olive fruit fly in the framework of an integrated pest management program.
Additional information
Dottorato di ricerca in Scienze delle produzioni vegetali e animali
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