© Benaki Phytopathological Institute
Persistence of insecticides in qat leaves
53
ent study sought to determine the residue
dissipation of the insecticides most used in
the production of qat (imidacloprid, acet-
amiprid and methomyl) to control jassids,
thrips and mites. To the best of our knowl-
edge, this is the first work on the residues of
these three insecticides in qat.
Materials and Methods
The commercial formula of selected insec-
ticides were purchased from a local market
in Jazan, KSA: imidacloprid (Imidor 200 g L
-1
)
(Astrachem, KSA), acetamiprid (Deltaride
20% sp) (Delta, KSA), and methomyl (Lanet
90 WP) (Du Pont, China).
Field trials were conducted at a private
farm in the Fyfa Mountains area on the bor-
der zone between Yemen and Saudi Arabia
(17° 15’ 3.76” N, 43° 7’ 56.46” E). Four separat-
ed plots of ten trees each, with a buffer zone
of 10–15 m between plots were selected for
this study. Consequently, the selected trees
were labeled for each treatment. Trees were
healthy, 10–12 years old, and were not treat-
ed with any pesticide for the last 4 years, as
declared by the farm’s owner. One plot was
considered to be a control and treated only
with tap water, while other plots were sep-
arately treated with the investigated insec-
ticides at the recommended application
rates. The applied concentrations of pesti-
cides in the sprayed solutions were 1.25 ml
L
-1
, 0.5 g L
-1
, and 0.5 g L
-1
for imidacloprid, ac-
etamiprid, and methomyl, respectively. The
total sprayed solution was 10 L for each plot
using a hand-operated sprayer (Mythos, Ita-
ly). All trees were treated until run-off.
For each treatment, leaves and buds
were sampled from the four sides and top
of each qat tree; an approximate total of 500
g of green qat leaves and buds were collect-
ed in a plastic bag from each plot at time 0
(1 h post-application) and 1, 3, 7, 12, 19, 26,
and 37 days after application. At each of the
specified times, collected samples (from
treated and control plots) were placed in
a field cooler at 4
o
C and transferred to the
laboratory. Accumulated precipitation dur-
ing the experiment was 53.1 mm; the mean
air temperature was 29.7
o
C (Fig. 1).
Upon arrival to the laboratory, each sam-
ple was chopped separately using a domes-
Figure 1.
Weather parameters at the research farm of qat during the period of the insectiside residue field experiment.
