© The Authors, 2023, Published by the Universidad del Zulia
*Corresponding author: gsarmientos@unsa.edu.pe
Guido Sarmiento-Sarmiento
*
Horacio Manrique-Nuñez
Luis Lipa-Mamani
Rev. Fac. Agron. (LUZ). 2023, 40(1): e234004
ISSN 2477-9407
DOI: https://doi.org/10.47280/RevFacAgron(LUZ).v40.n1.04
Crop production
Associate editor: Dra. Gretty R. Ettiene Rojas
University of Zulia, Faculty of Agronomy
Bolivarian Republic of Venezuela
Keywords:
Persea americana
Neonicotinoide
Periodo de carencia
Plaguicida
Residues and dissipation of imidacloprid in avocado fruit
Residualidad y disipación de imidacloprid en frutos de palto
Residualidade e dissipação do imidaclopride no abacateiro
Universidad Nacional de San Agustín de Arequipa. Facultad
de Agronomía, Urb. Aurora s/n; Arequipa, Perú.
Received: 04-09-2022
Accepted: 03-12-2022
Published: 26-12-2022
Abstract
Imidacloprid is a neonicotinoid insecticide used to control insect pests
in avocado (Persea americana); its excessive application could generate
residues above the maximum residue limits (MRL) in the fruit, causing
a serious health risk to consumers. The objective of this work was to
determine the residues and dissipation of imidacloprid in avocado fruit,
Hass variety. The treatments were the doses of imidacloprid (0.5, 1.0 and
1.5 mL.L
-1
) under the commercial formulation Thunder 350SC and the
forms of application (sprayed to foliage and drip at the foot of the
plant). There were six treatments in a completely randomized
experimental design with three replications and 18 experimental units
(plants). Quanti ication was by HPLC (QuEChERS). The evaluations
were carried out on two matrices (avocado fruit peel and pulp) at 1, 3, 7
and 14 days after the application of Imidacloprid. The application of the
0.5 mL.L
-1
dose by drip at the foot of the plant resulted in lower residual
and a higher percentage of dissipation in both matrices, higher daily
dissipation rate in the pulp, with imidacloprid concentrations that did not
exceed the MRL (0.7 mg.kg
-1
). The application of 1.5 mL.L
-1
by spraying
resulted in higher residual, and in a lower percentage of dissipation in both
matrices, with imidacloprid concentrations in the peel exceeding the MRL
at 7 and 14 days. In the pulp, none of the treatments exceeded the MRL.
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ). 2023, 40(1): e234004. Enero-Marzo. ISSN 2477-9407.2-7 |
Resumen
Imidacloprid es un insecticida neonicotinoide que se utiliza para
controlar insectos plaga en el cultivo de palto (Persea americana),
su aplicación excesiva pudiera generar residuos por encima de los
límites máximos de residuos (LMR) en los frutos ocasionando un
grave riesgo para la salud de los consumidores. El objetivo de este
trabajo, fue determinar la residualidad y disipación de imidacloprid
en frutos de palto, variedad Hass. Los tratamientos fueron las dosis
de Imidacloprid (0,5; 1,0 y 1,5 mL.L
-1
) bajo la formulación comercial
Thunder 350SC y las formas de aplicación (Asperjado al follaje y
goteo a pie de planta). Se conformaron seis tratamientos en un
diseño experimental completamente al azar con tres repeticiones, 18
unidades experimentales (plantas). La cuanticación fue mediante
HPLC (QuEChERS). Las evaluaciones se realizaron en dos matrices
(cáscara y pulpa de frutos de palto) a 1, 3, 7 y 14 días de la aplicación
de imidacloprid. La aplicación de la dosis de 0,5 mL.L
-1
por goteo
a pie de planta originó menor residualidad y mayor porcentaje de
disipación en ambas matrices, mayor tasa de disipación diaria en
la pulpa, con concentraciones de imidacloprid que no superaron
el LMR (0,7 mg.kg
-1
). La aplicación de 1,5 mL.L
-1
por aspersión
ocasionó mayor residualidad, menor porcentaje de disipación en
ambas matrices, con concentraciones de imidacloprid en la cáscara
que superaron los LMR a 7 y 14 días. En la pulpa ninguno de los
tratamientos superó el LMR.
Palabras clave: Persea americana, neonicotinoide, periodo de
carencia, plaguicida.
Resumo
Imidaclopride é um inseticida neonicotinóide usado para
controlar pragas de insetos no abacate (Persea americana), sua
aplicação excessiva poderia gerar resíduos acima dos limites
máximos de resíduos (LMR) na fruta, causando um sério risco à
saúde dos consumidores. O objetivo deste estudo foi determinar o
resíduo e a dissipação do imidaclopride na fruta abacate, variedade
Hass. Os tratamentos foram doses de imidaclopride (0,5, 1,0 e 1,5
mL.L
-1
) sob a formulação comercial Thunder 350SC e a formas de
aplicação (pulverizado sobre a folhagem e gotejado no pé da planta).
Houve seis tratamentos em um projeto experimental completamente
aleatório com três réplicas, 18 unidades experimentais (plantas). A
quanticação foi feita por HPLC (QuEChERS). As avaliações foram
realizadas em duas matrizes (casca de fruta abacate e polpa) em 1,
3, 7 e 14 dias após a aplicação do imidacloprid. A aplicação da dose
de 0,5 mL.L
-1
por gotejamento no pé da planta resultou em menor
resíduo e maior porcentagem de dissipação em ambas as matrizes,
maior taxa de dissipação diária na polpa, com concentrações de
imidaclopride que não excederam o LMR (0,7 mg.kg
-1
). A aplicação
de pulverização de 1,5 mL.L
-1
resultou em maior resíduo, menor
porcentagem de dissipação em ambas as matrizes, com concentrações
de imidaclopride na casca excedendo os LMRs aos 7 e 14 dias. Na
polpa, nenhum dos tratamentos excedeu o LMR.
Palavras-chave: Persea americana, neonicotinoide, período de
retirada, pesticida.
Introduction
The application of pesticides is a common practice in conventional
agro-productive systems of food production (Bondareva and Fedorova,
2021). However, there is sucient information that demonstrates the
risks involved in their indiscriminate use, which could cause negative
eects on human health and deterioration of agricultural ecosystems
(Chandra et al., 2021; Zikankuba et al., 2019; Durán-Quirós et al.,
2017; Ettiene et al., 2017).
Additionally, overdosing or non-compliance with the waiting
periods of insecticides can generate residues not allowed in food
(Durán-Quirós et al., 2017) that when exceeding the MRL become
contaminating substances that could originate adverse eects on
human health (Pereira et al., 2021, Yilmaz, 2017).
Therefore, a criterion of great importance in the use of an
insecticide is the knowledge of the residues and their dissipation period
in the harvested food (Chandra et al., 2021). On the other hand, the
toxic eect and the dissipation period of insecticide residues depend
on the characteristics of the applied product, and are conditioned by
physical, mechanical, chemical, biological, and climatological factors
of the environment (Zikankuba et al., 2019).
Imidacloprid is the most widely used neonicotinoid insecticide
in the phytosanitary management of various crops (Pang et al.,
2020). Nowadays, its use is extensive for the control of various
pests in agricultural production, causing signicant amounts of
residues in harvested food and the environment (Peng et al., 2021;
Zhou et al., 2021) with impacts and risks to the health of consumers
and contamination of ecosystems (Hladik et al., 2018; Fernández
and Giménez, 2005). These insecticides are degraded by multiple
hydroxylation reactions and aromatic ring cleavage, forming non-
absorbent intermediates such as carbon dioxide and other minerals
(Joice et al., 2019).
Avocado is a product with great acceptance in international
markets (Zambrano, 2014). Its management in the eld requires great
care regarding the insecticides used for pest control, because they
could be contaminated with persistent residues (García-Vargas et al.,
2020).
In Peru, imidacloprid is the most frequently neonicotinoid used
for plant protection of avocado crops (Collavino and Giménez,
2008; Jawad and Hermize, 2020; Mohapatra et al., 2019; Peng et
al., 2021). According to Castillo et al. (2020), many growers make
insecticide applications indiscriminately to protect their crops without
considering the toxicity of the product due to chemical residues, so
there is concern from avocado fruit producers regarding the presence
of insecticide residues, to comply with international marketing
standards, especially for exports, due to the fact that these markets
are very demanding in terms of food safety (Delgado-Zegarra et al.,
2018).
Previous reports (Agriquem, 2021), reported residues of
imidacloprid, spirotetramat, prochloraz, 2-4-6 trichlorophenol,
and methomyl in avocado lots exported from Peru to countries of
the European Union. Therefore, the quantitative assessment of
imidacloprid residues according to the form of application is an
essential issue for avocado growers, in order to comply with national
and international requirements regarding the MRL for marketing.
In this context, the objective of the research was to determine
the residues and dissipation of imidacloprid in avocado fruit (Persea
americana) of the Hass variety by the eect of the application of the
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Sarmiento-Sarmiento et al. Rev. Fac. Agron. (LUZ). 2023 40(1): e234004
3-7 |
insecticide in three doses and two forms of application: sprayed to
foliage and drip at the foot of the plant.
Materials and methods
Trial location
The research was carried out in an avocado plantation of the Hass
variety of the Majes Irrigation of Arequipa, Peru; located at latitude
16°21′11″ (S), longitude 72°11′27″ (W) and 1410 masml altitude,
where an arid zone climate with humidity deciency prevails in all
seasons of the year. During the research period, the average daily
temperature was between 19 and 24
o
C, and relative humidity was
between 48 and 52%; no precipitation was recorded.
Edaphic characteristics and avocado plantation management
The soil texture was loamy sand; sand: 84.8 %; silt: 8.8 %;
clay: 6.4 %; organic matter: 1.32 %; total N: 0.07 %; available P:
21.25 mg.kg
-1
; total K: 285.5 mg.kg
-1
; pH: 7.2; EC: 0.85 mS.cm
-1
;
C.I.C.: 8.56 cmol.kg
-1
; these characteristics were suitable for avocado
planting.
The avocado plantation was in the second year of production
with a density of 500 plants.ha
-1
, and with a spacing of 5 x 4 m. To
enhance production, nutrients were applied via fertigation at doses of
300, 45, 250, 10, and 50 kg.ha
-1
of N, P, K, Mg, and Ca, respectively.
The Thunder 350 SC commercial formulation was used, whose
active ingredient is imidacloprid (350 g.L
-1
) of the neonicotinoid
family. It is a systemic insecticide that acts by contact and ingestion
for the control of “spider mites” (Panonychus citri, Oligonychus
spp.), and stinging-sucking insects such as thrips and bugs, pests of
great importance in the avocado crop at the doses, and in the forms
indicated in the treatments. The commercial formulation Thunder 350
SC refers to an MRL (Maximum Residue Limit) of 0.7 ppm (mg.kg
-
1
), and a withdrawal period of seven (7) days. FAO and WHO have
not yet approved MRL for imidacloprid on avocados. Copper sulfate
was also applied for rot prevention via the irrigation system at a dose
of 4 L.ha
-1
. Fruits were harvested using scissors and leaving 3 to 5 mm
of peduncle on each fruit.
Experimental design and statistical analysis
Six treatments (three doses in two forms of application) were
randomly applied in the avocado plantation in a completely
randomized experimental design with three replications, and 18
experimental units (avocado plants). For the treatments studied,
imidacloprid insecticide was applied at three doses: 0.5, 1.0, and
1.5 mL.L
-1
, under the commercial formulation Thunder 350SC in
two forms of application: sprayed to the foliage (AAF), and drip at
the foot of the plant (GPP). The spray application was carried out
using a knapsack sprayer and the drip application was via an adapted
irrigation system. For this, the insecticides were diluted in water
and applied homogeneously in the spray matrix of each tree in an
equivalent volume of 800 L.ha
-1
. In the drip system, 350 L.ha
-1
were
used. Imidacloprid was applied only once during the period of growth
and fruit maturity (105 days after fruiting).
The records of the evaluations were subjected to analysis of
variance. Tukey’s multiple range test (p < 0.05) was used to establish
signicant dierences between treatments. A simple linear regression
analysis with logarithmic arrangement was performed to elaborate the
imidacloprid dissipation curves. Statistical analyses were performed
with RStudio.
Sampling of avocado fruits
Avocado fruits were collected during the period of growth and
maturity, the samples were taken randomly on the rst, third, seventh,
and fourteenth day of the application of the treatments; three avocado
fruits were sampled for each experimental unit, these were taken
from the central part of the plant in the middle of the vegetative
period. The samples were placed in a cooler with ice at an average
temperature of 4
o
C, and transferred to the Agro-environmental
Analysis Laboratory of the National University of Saint Augustine,
Peru for the corresponding analytical determinations.
Analytical determination of imidacloprid
Reagents, materials, and equipment
The HPLC-grade imidacloprid standard was purchased from
Sigma Aldrich with a purity percentage of 99.5 %. The solvents
used were acetonitrile and methanol (HPLC grade). Ultrapure water
with a resistivity of 18.2 MΩ.cm
-1
obtained from the Simplicity UV
Merck Millipore purication system was used. QuEChERS AOAC
2007.01 dispersion and extraction kits, were used; a Purospher Star
C18 column (RP-18e 150 x 4.6 mm, 5 µm), a Hitachi High-Tech
Chromaster for high-performance liquid chromatography with diode
array (HPLC - DAD), and a nitrogen concentrator (Labtech Multivap 6).
Extraction and cleaning of the sample
For the extraction, 10.0 g of homogenized sample was used
with 10 mL of acetonitrile (ACN) adding the QuEChERS AOAC
2007.01 extraction kit (6 g of MgSO4, 1.5 g of sodium citrate), it was
manually shaken for one minute and centrifuged for three (3) minutes
at 3,300 rpm with a universal centrifuge 320, Hettich. Dispersive
solid phase extraction (d-SPE) was used to clean up the extracts;
for that, the supernatant of the product of the previous extraction
was used, adding the QuEChERS AOAC 2007.01 dispersion kit
(50 mg secondary primary amine, 150 mg MgSO4), the mixture
was manually shaken for one minute and centrifuged for three (3)
minutes at 3,300 rpm. Then, 3.5 mL of the upper layer was taken,
subsequently, the sample was concentrated to dryness using N
2
(g),
then the residue, was reconstituted with the mobile phase to one (1)
mL, nally, the resulting solution was ltered with a 45 μm Nylon
lter for subsequent analysis by HPLC - DAD (AOAC, 2007).
Separation of imidacloprid by high-performance liquid
chromatography (HPLC)
For the separation of imidacloprid by HPLC, a mobile phase
composed of acetonitrile (100%) was employed, using a diode
array detector (DAD) at a wavelength of 270 nm, identifying the
imidacloprid signal with a retention time of 4.7 min. The method
was validated to determine the parameters of linearity, sensitivity,
precision, and accuracy (Aguirre et al., 2001).
A calibration curve was prepared from the pure imidacloprid
standard, using six concentrations (0.2; 0.5; 0.8; 1.1; 1.4, and 1.7
mg.L
-1
) obtaining a coecient of determination (r
2
) of 0.9995; with
limits of detection (LOD) and quantication (LOQ) of 0.0116, and
0.0156 mg.L
-1
, respectively. The relative standard deviation (RSD)
was 0.46%. The accuracy calculated by the percent recovery method
(%R) was 97.54 %. The results prove that the method is linear (r
2
>
0.995), precise (RSD < 2.7%), and accurate with a %R between 90
and 110 % (Aguirre et al., 2001).
Residues of imidacloprid
The concentration of imidacloprid in the peel (exocarp), and pulp
(mesocarp) of avocado fruit was determined. Records were taken 1,
3, 7, and 14 days after the application of treatments. The results were
expressed in mg.kg
-1
.
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Rev. Fac. Agron. (LUZ). 2023, 40(1): e234004. Enero-Marzo. ISSN 2477-9407.4-7 |
Daily dissipation rate of imidacloprid
The daily dissipation rate was obtained by linear regression,
transforming the data by means of the following logarithmic
equation:
Where:
Y: dependent variable (calculated daily dissipation rate); B0:
corrected dissipation values; B1: dissipation rate; X : elapsed time
after imidacloprid application.
For each treatment, a dissipation curve was constructed with
the corresponding equation, using the corrected dissipation values.
Results and discussion
Residues of Imidacloprid in peel and pulp of avocado fruit
Statistical dierences were observed among treatments in the
four evaluation periods (table 1) with coecients of variability
between 2.45 % and 7.79 %. In all evaluations on peel and pulp, a
tendency to decrease the initial imidacloprid concentration (1st day)
was evidenced as the evaluation time increased (3, 7, and 14 days).
In the peel, the highest initial concentration of imidacloprid
was 0.923 mg.kg
-1
by the application of the 1.5 mL.L
-1
AAF dose.
After 14 days it decreased to 0.726 mg.kg
-1
, representing 21.3 %
dissipation. The lowest residual was observed with the application
of the 0.5 mL.L
-1
GPP dose with an initial concentration of 0.285
mg.kg
-1
, and after 14 days it decreased to 0.175 mg.kg
-1
, representing
38.6 % dissipation.
Imidacloprid was not detected in the pulp on the rst day of
evaluation. On the third day, the highest concentration (0.563
mg.kg
-1
) was recorded by the application of 1.5 mL.L
-1
AAF, and
on the fourteenth day, it decreased to 0.384 mg.kg
-1
with 35.3 %
dissipation. The lowest residual in the pulp was observed after
three days when applying the 0.5 mL.L
-1
GPP dose (0.086 mg.kg
-1
),
and after 14 days it decreased to 0.022 mg.kg
-1
achieving 74.4 %
dissipation.
According to Zhai et al. (2022) and Durán-Quirós et al. (2017),
pesticide residues gradually decrease over time, and the rate of
decrease varies by various environmental factors, and plant and
pesticide characteristics.
The trend in the results showed that the residues of imidacloprid
were lower when the doses were applied by drip application at the
foot of the plant, both in the peel and in the pulp. The peel had a
higher concentration of imidacloprid than the pulp.
Table 1. Imidacloprid residues (mg.kg
-1
) in peel and pulp of avocado fruit in four evaluation periods after application.
Treatments
1 day 2 days 7 days 14 days
Peel Pulp Peel Pulp Peel Pulp Peel Pulp
0.5 mL.L
-1
AAF 0.784±0.071c 0 0.705±0.010d 0.153±0.004b 0.612±0.015c 0.128±0.006c 0.428±0.018c 0.105±0.007c
0.5 mL.L
-1
GPP 0.285±0.007a 0 0.203±0.009a 0.086±0.006a 0.198±0.008a 0.053±0.003a 0.175±0.008a 0.022±0.004a
1.0 mL.L
-1
AAF 0.856±0.073cd 0 0.790±0.004e 0.30±0.0074d 0.768±0.014d 0.288±0.004d 0.684±0.041d 0.203±0.011d
1.0 mL.L
-1
GPP 0.362±0.051a 0 0.242±0.005b 0.109±0.007a 0.206±0.01a 0.083±0.005b 0.193±0.004a 0.065±0.003b
1.5 mL.L
-1
AAF 0.923±0.028d 0 0.865±0.027f 0.563±0.012e 0.783±0.020d 0.475±0.006e 0.726±0.009d 0.384±0.005e
1.5 mL.L
-1
GPP 0.517±0.017b 0 0.422±0.010c 0.198±0.012c 0.376±0.004b 0.124±0.007c 0.291±0.006b 0.091±0.004c
CV (%) 7.79 - 2.45 3.66 2.66 2.79 4.57 4.31
Equal letters in each column indicate that there are no signicant statistical dierences between treatments according to Tukey (p ≤ 0.05). CV: coecient of variability.
AAF: sprayed to the foliage. GPP: drip at the foot of the plant. ±: standard deviation.
= 0
1
With respect to the percentage of imidacloprid dissipation,
this was higher in the pulp than in the peel. The application of
imidacloprid doses by drip resulted in a higher percentage of
dissipation compared to the application by spraying to the foliage.
Regarding the best performance of the 0.5 mL.L
-1
GPP dose,
Collavino and Giménez (2008) explained that the imidacloprid
insecticide is characterized by a systemic mode of action, therefore
its slow dosage form would facilitate its dissipation; on the other
hand, spray applications at high doses may result in a greater residual
and lower percentage of dissipation. Although, Zhou et al. (2021)
report that the dierences in the initial and nal concentration of
imidacloprid for each treatment can be attributed to the diameter
and mass of the avocado fruit, the smaller fruits having a larger
specic surface area have a greater accumulation of the pesticide;
and as the diameter of the fruit increases, the concentration of the
pesticide decreases. On the other hand, Fernandez and Gimenez.
(2005) indicate that foliar application of pesticides generally
causes a good portion of the product to be deposited on the soil,
but the adherence to the avocado fruit peel associated with the high
temperature and low atmospheric relative humidity would have
caused a higher initial concentration of imidacloprid.
A greater residual of imidacloprid was obtained in the peel
in relation to the pulp; in this regard, Pang et al. (2020) pointed
out that in fruits for daily consumption, the peel acts as a natural
protector against external agents; therefore, it is obvious to assume
that the residues of imidacloprid would be retained in the peel and
only a minimal amount would penetrate the pulp. In this sense,
Joice et al. (2019) and Pereira et al. (2021), point out that in
the initial concentration or initial deposit, the lower layer of the
pesticide is strongly adhered to the plant surface. Likewise, Pang et
al. (2020) and Zikankuba et al. (2019), emphasize that the physical
characteristics, chemical composition, and presence of waxes
of the plant or fruits aect the retention of a pesticide, and in the
case of avocado fruit, on the surface of its peel there is a dense,
thick and uniform layer of wax that covers the epidermal surface
without interruption (Barrientos et al., 1996), so this layer would
have allowed a uniform adherence of imidacloprid when the doses
were applied by spraying to the foliage causing greater residual on
the peel, compared to a drip application at the foot of the plant. In
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Sarmiento-Sarmiento et al. Rev. Fac. Agron. (LUZ). 2023 40(1): e234004
5-7 |
avocado pulp, applications of all treatments did not exceed the MRL
for imidacloprid in all evaluation periods.
On avocado peel (gure 1), on the rst day of evaluation, all doses
applied by spraying to the foliage exceeded the MRL (0.7 mg.kg
-1
)
for imidacloprid indicated by the manufacturer. None of the doses
applied exceeded the MRL (1.0 mg.kg
-1
) proposed by the Code of
Federal Regulations (CFR, 2022). FAO and WHO, have not yet
established MRL for imidacloprid on avocado.
Figure 1. Residues of imidacloprid (mg.kg
-1
) in avocado peel for
each treatment compared to the MRL.
At seven days, considered to be the withdrawal period for the
commercial formulation, the imidacloprid doses of 1 and 1.5 mL.L
-1
AAF exceeded the MRL. At 14 days, only the 1.5 mL.L
-1
AAF dose
exceeded the MRL. In the peel, none of the imidacloprid treatments
applied by drip exceeded the MRL in all evaluation periods. In this
regard, Durán-Quirós et al. (2017) indicate that the withdrawal period
is the period of time allowed for a pesticide to degrade below the MRL
and is inuenced by climatic conditions and the pernicious eect cycle
of the pesticide. The Peruvian Technical Sanitary Standard (NTP:128/
MINSA/2016/DIGESA), indicates that the MRL for imidacloprid in
avocado of the Hass variety is 1 mg.kg
-1
, according to PROMPERU
(2022), similar MRL is allowed for avocado exports to Europe, USA,
Canada, Chile, China, and Costa Rica; therefore, applications of all
treatments would not aect the sanitary quality of avocado for these
markets.
For the Japanese market, the MRL is 0.7 mg.kg
-1
(PROMPERU,
2022), in this case, the application of 1.5 mL.L
-1
AAF would limit its
commercialization due to the residues of imidacloprid detected at the
peel level 14 days after its application. At seven days, which is the
withdrawal period, the MRL in peel was also exceeded by applications
of 1.0 and 1.5 mL.L
-1
AAF, limiting its commercialization. In the
pulp, the MRL was not exceeded.
Daily dissipation rate of imidacloprid in the peel and pulp of
avocado fruit
In the peel, the highest daily dissipation rate was due to the eect of
the 0.5 mL.L
-1
AAF dose (table 2), for each day that the concentration
of imidacloprid elapsed, it decreased by 0.01993 mg.kg
-1
. The lowest
dissipation rate was for the application of 1.0 mL.L
-1
AAF.
Treatments
Peel Pulp
TDD VDC TDD VDC
0.5 mL.L
-1
AAF -0.01993 0.91744651 -0.014621 0.45884721
0.5 mL.L
-1
GPP -0.01319 0.55254522 -0.054234 0.40621204
1.0 mL.L
-1
AAF -0.006944 0.93365153 -0.016632 0.63727946
1.0 mL.L
-1
GPP -0.016733 0.60032386 -0.019792 0.39892614
1.5 mL.L
-1
AAF -0.007639 0.96262052 -0.014887 0.81023577
1.5 mL.L
-1
GGP -0.018031 0.7466625 -0.029368 0.52251844
TDD: Daily dissipation rate. VDC: Corrected dissipation values. AAF: sprayed
to the foliage. GPP: drip at the foot of the plant.
In the pulp, the highest rate of dissipation of imidacloprid was by
the application of the 0.5 mL.L
-1
GPP dose, for each day elapsed, the
concentration of imidacloprid decreased by 0.054234 mg.kg
-1
. It was
found that in the pulp the dissipation rate was higher with respect to
the dissipation in peel.
The dissipation curve model corresponds to a rst order
logarithmic equation in both matrices evaluated. Figure 2 shows
a trend generated by the application of the treatments where the
concentration of imidacloprid in the avocado peel dissipates gradually
as the application time elapses, being more accentuated from three
days after the application of the treatments (DDAT).
Figure 2. Dissipation curve of imidacloprid in avocado peel. AAF:
sprayed to the foliage. GPP: drip at the foot of the plant.
T1: 0.5 mL.L
-1
AAF. T2: 0.5 mL.L
-1
GPP. T3: 1.0 mL.L
-
1
AAF. T4: 1.0 mL.
L-1
GPP. T5: 1.5 mL.L
-1
AAF. T6: 1.5
mL.L-
1
GPP
.
.
The gure 3 shows the same trend in the pulp but with greater
evidence from the seven DDAT.
Figure 3. Dissipation curve of imidacloprid in avocado pulp.
AAF: sprayed to the foliage. GPP: drip at the foot of the
plant. T1: 0.5 mL.L
-1
AAF. T2: 0.5 mL.L
-1
GPP. T3: 1.0
mL.L
-1
AAF. T4: 1.0 mL.L
-1
GPP. T5: 1.5 mL.L
-1
AAF. T6:
1.5 mL.L
-1
GPP.
Table 2. Daily dissipation rate of imidacloprid (mg.kg
-1
) and
corrected dissipation values in the peel and pulp of
avocado fruit for each treatment.
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ). 2023, 40(1): e234004. Enero-Marzo. ISSN 2477-9407.6-7 |
The gure 4 shows the logarithmic dissipation of imidacloprid
for the two types of application, evidencing that AAF and GPP also
caused a staggered dissipation in the peel and pulp of the avocado as
time increases.
Figure 4. Logarithmic dissipation of imidacloprid for the two
types of application (spray and drip) on avocado peel
and pulp.
In a study of imidacloprid dissipation by Zhai et al. (2022) in
Chinese onion (Allium tuberosum) they observed dissipation dynamics
consistent with rst order kinetics, with nal residual levels between
0.00923 and 0.166 mg.kg
-1
below the MRL (1 mg.kg
-1
) with a risk
assessment index <1 indicating that they are safe for consumption.
Similar results were obtained by Mohapatra et al. (2019) in
the evaluation of imidacloprid residue levels in pomegranate fruits
(Punica granatum) for two years, they found rst order reaction
kinetics with a degradation half-life of 8 to 11.1 days; the MRL of
imidacloprid in pomegranate were lower than their MRL (1 mg.kg
-1
),
with a pre-harvest interval of only one day. On the other hand, Jawad
& Hermize (2020) in an analysis of imidacloprid residues on fruits of
sweet Karisma bell pepper (Capsicum annum L), reported that after
eight days, the residual of imidacloprid was 0.07 mg.kg
-1
lower than
the MRL.
According to Zhai et al. (2022) and Hladik et al. (2018), the
agroecological zone where a pesticide is applied would have its eect
mainly on the daily dissipation rate of the residue. In this regard,
Pereira et al. (2021), and Zhou et al. (2021), highlight that in arid areas,
high temperatures, and wind action would be the determining factors
in pesticide dissipation. In the same order of ideas, Zhou et al. (2021),
and Peng et al. (2021) state that the dissipation dynamics establishes
a rapid initial decrease depending on climatic conditions. According
to Pang et al. (2020), the dissipation of systemic insecticides such as
imidacloprid in avocado fruit pulp is greater than the dissipation of
insecticides in the peel; this degradation is complex and the rate of
internal metabolization is variable and is determined by enzymatic
actions, characteristic of plant tissue. However, Gonzalez (2009)
refers that the residues and dissipation of a pesticide are inuenced
by the application coverage and the size of the application drop; the
smaller the pesticide drop, the greater the persistence of the pesticide
and therefore the greater the residual. On the other hand, Mohapatra
et al. (2019), state that the increase in temperature facilitates several
processes involved in the dissipation of an insecticide, so an increase
in temperature favors the solubility of the insecticide. Imidacloprid
presents high solubility in water, favoring its dissipation.
The information provided by this research is of utmost importance
for phytosanitary safety and food safety, demonstrating that the
manufacturer’s recommendation regarding the insecticide withdrawal
period (7 days) is not met when 1.0 and 1.5 mL.L
-1
AAF are applied,
because the residual of imidacloprid in the peel exceeded the MRL.
No levels exceeding the MRL were detected in the pulp. In this sense,
it is advisable for future research to develop a more appropriate and
representative withdrawal period for avocado cultivation in arid areas
where its cultivation is of great importance.
Conclusions
It was determined that the application of imidacloprid by drip at
the foot of the plant at a dose of 0.5 mL.L
-1
caused the lowest residual,
and the highest percentage of dissipation in the peel and pulp of
avocado fruits, reaching the highest daily dissipation rate in the pulp.
Spraying imidacloprid to the foliage at a dose of 1.5 mL.L
-1
caused
the highest residual, and the lowest percentage of dissipation in the
peel and pulp of the fruits, generating residues of imidacloprid in the
peel that exceeded the MRL. None of the treatments exceeded the
MRL in the pulp. The dissipation rate was higher in the pulp than in
the peel. The imidacloprid dissipation curve model was t to a rst-
order logarithmic equation.
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