DESERT LOCUST AND ITS IDENTIFICATION
The Desert Locust is a large and
highly feared acridian that invades many countries worldwide. In invasion
periods, swarms sometimes reach southern Europe,
Africa north of the equator, the Arabian Peninsula and the Indo-Pakistan region. In
recession periods, solitary locusts take refuge in the following outbreak zones:
the
Indo-Pakistani border, where wind currents help to concentrate high numbers of
locusts; (ITCZ).
coastal
regions along the Red Sea and the Gulf of Aden where the precipitation regime can provide
suitable year-round locust breeding conditions ;
Near
some mountain massifs where runoff can create suitable locust sites (central
and southern Saharan massifs, southern edge of the Atlas
mountains, western side of the Oman mountains, valleys of the
Mekran in Pakistan
and in Iran).
Solitarious Desert Locusts are harmless to crops whereas in the gregarious phase their voracity, massive population movements, vast invasion area and swarm densities can be redoubtable. Phase transformation occurs when the density threshold is above 250 - 500 adults/ha and from 0.5 to 5 hoppers/m2.
Solitarious locusts only breed in desert zones whereas gregarious forms are more flexible in their ecological requirements and able to colonize less xeric habitats thus covering a much greater surface area.
This species mainly gathers in dry environments with open steppe vegetation. The optimal rainfall range for the Desert Locust is 25 - 50 mm per month. Solitary locusts fly at night during calm periods when temperatures are above 25'C to outbreak zones reactivated by the rains. They can be captured with light traps at such times. In contrast, swarms migrate during the day which enables them to take advantage of updraughts to cross orographic barriers and colonize areas thousands of kilometres away. The seasonal migration patterns of gregarious locusts are quite well established.
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