A detailed analysis of a
Desert Locust Upsurge in Saudi Arabia
(Nov 1996 - May 1997)
Locust
infestations pdf
version
(441kb) NOVEMBER 1996.
Solitary adults were first reported on
the Red Sea coastal plains in November 1996. The
origin of these adults is thought to be from those
escaping control operations against hopper bands
and adult groups in the interior of Yemen during
the autumn. Most of the adults were probably drawn
into the Red Sea Trench on southerly winds
associated with a strong and persistent depression
over the northern Red Sea in mid November 1996. The
majority of these landed on the coastal plains of
Saudi Arabia and probably dispersed over a wide
area from Al-Lith in the south to Al-Wajh in the
north, making it difficult to find them. JANUARY
1997. Small scale breeding first
occurred shortly after the rains, primarily near
Al-Lith and Badr, producing a new generation of
solitary adults that appeared from late January
onwards. Densities were still relatively low,
mostly from 1-3 per ha with a few locations
reporting up to 100 per ha. In mid January, widespread light to moderate
rains fell on the coast north of Jeddah. Adults may
have concentrated in this area over the next few
weeks, increasing in density to nearly 1-2 adults
per m2 (10,000/ha) which was probably enough to
induce a partial phase change from solitarious to
transiens. Laying occurred by solitary adults in
the Khulais and Badr areas shortly after the
rains. FEB-MARCH.
Heavier laying by solitary adults and groups of
transiens occurred in late February in Al-Lith,
Usfan-Tuwwal, Khulais, Rabigh, and during the first
half of March in Usfan-Tuwwal, Masturah, Badr,
Yanbu, and Umm Lajj. Breeding during the latter
period was supplemented by low density mature
swarms reportedly coming from the western shore of
the Red Sea on 8-15 March. The swarms were
estimated to vary in size from 5-50 km2 with
densities of 5-20 adults/m2 and laid upon arrival.
Other laying adult densities were estimated to be
about 2-5/m2. Consequently, locust numbers rapidly
increased during this period.
(March-June
cont.)
