© Benaki Phytopathological Institute
Persistence of insecticides in qat leaves
57
increases significantly with the progression
of the summer months (Reeve
et al.,
1992)
due to the slow growth of plants and, con-
sequently, less efficiency in the degradation
of the pesticides. The initial residual concen-
tration in qat leaves was higher than results
reported in tomatoes (1.54 mg kg
-1
) (Gamba-
corta
et al.,
2005) and 5.61–8.42 mg kg
-1
in
okra fruits treated at the recommended and
double-the-recommended doses, respec-
tively (Aktar
et al.,
2008). Methomyl residue
concentrations ranging from 0.01 to 1.42 mg
kg
-1
were detected in grape samples collect-
ed from the Aegean region in Turkey and in
some vegetables (arugula, eggplant, bean,
cucumber, leek, mushroom, onion, and
pepper); at concentrations ranging from
0.01 to 2.13 mg kg
-1
; the residues in all sam-
ples were below the MRL of 5 mg kg
-1
(Bakir-
ci
et al.,
2014). The rapid dissipation of meth-
omyl and its relatively short half-life led to
decrease the residues below the MRL value
within only 1 day after application.
Conclusions
The present study demonstrates that the
neonicotinoid insecticides imidacloprid and
acetamiprid have similar dissipation path-
ways in qat leaves; their persistence was
significantly higher than the carbamate in-
secticide methomyl. Half-life values for imi-
dacloprid, acetamiprid andmethomyl, when
applied at recommended dosages on qat
trees, were 12.2, 11.7 and 5.1 days, respec-
tively. Our results showed that the residues
of the investigated pesticides were below
the MRL for lettuce 7 days post-application
for imidacloprid and 1 day post-application
for acetamiprid and methomyl. In view of
the increased consumption of qat and the
scarce information about the dissipation of
pesticides in this plant, more studies are re-
quired to assess the risk of human exposure
to pesticides by chewing qat leaves.
AJ Al-Rajab designed the experiments, data in-
terpretation, manuscript writing, and submis-
sion corresponding. AM Alhababy contribut-
ed in experiments design, treatments, samples
preparation, data collection and interpreta-
tion. T. AlFaifi contributed in pesticides’ treat-
ment, sampling, lab preparation and data col-
lection.
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