"ملف ٣٧/١٦أ- I تدابير مكافحة الجراد الصحراوي" [ظ‎‎٢‎٣‎٤] (٩٠٠/٤٦٨)

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this gives a screen three feet high from the ground after allowing six to
eight inches to lie on the ground. For bare country or short vegetation
a narrower width of cloth would be sufficient. The supports recommended
consist of half-inch bar iron, sharpened to a point at the bottom and bent
into a loop at the top. These supports are placed firmly into the ground
at the required distances, and the screens are stretched tight and suspended
from these. It is important that the suspending rods should be on the
opposite side of the screen from the advancing locust band. They should
be of sufficient length to support the screens at the required height, after
at least six inches have been driven into the ground.
Such screens can be quietly and quickly run up where required, with
out checking the advance of the swarm of hoppers towards the trenches.
They completely dispense with the need for side stops, reduce the labour
required for driving the swarm, increase the efficiency of each drive and
accelerate control operations. They also reduce the labour expended upon
digging* as in place of a long trench, a deeper broader pit, sufficient to con
tain the swarm, is dug at the apex of the converging screens.
Locust screens are intended primarily to deal with large swarms of
hoppers, and have been issued in units of 240 yards, made up of ten
lengths of 24 yards each. One such set, properly disposed, will deal with a
swarm frontage of 1::0 to 150 yards. For large swarms two or more sets can
be combined in a series of angles along the frontage of the swarm.
Method 8.—Traps instead of pits or trenches
Canvas traps—Where the subsoil is rocky, or the digging of a pit is
otherwise impossible or difficult, a canvas structure in the form of a rec
tangular open box equal in height to the screens on the two sides and the
back, and similarly fitted with American oil-cloth, takes the place of the pit.
The hoppers enter it by means of a long, sloping canvas approach at the
front. It is efficient and saves much time and labour in pit digging but
is less simple to erect than the screens. Canvas traps will, however, be
essential to locust control by driving, in areas with shallow soil and rocky
sub-soil ; or if in the hot months the ground is so dry and hard as to be
impossible to dig.
Metal box traps.—Sheets of smooth metal can similarly be used to
replace digging of pits. The sheets are arranged on the ground in the form
of a box. Earth is piled up against the outside to make a road for the locusts
to enter.
Maintenance of the Surface of the Oil-cloth
If the polished surface of the oil-cloth becomes dirty, it affords a foot
hold for the locusts and they can climb over it. The slipperiness can be
maintained by wiping the surface with a cloth which has been dipped in
kerosepe oil, T his should be done as often as proves necessary.
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