Dynamics of desert locust population in Pakistan


Erum Akbar

As swarms of locusts descended upon Karachi and spread from Malir and Korangi areas to other parts of the city on Monday. The federal and provincial authorities termed the recent activity as part of the creature’s migration process. The authorities confirmed the movement of swarms of locusts but denied that any attack on the crops in the city’s rural parts took place. According to FAO, Pakistan is an important front-line country for Desert Locust because it has summer and spring breeding areas. Summer breeding normally occurs in the deserts of Tharparkar, Khipro and Cholistan inSindh and southern Punjab provinces. The timing of summer breeding coincides with the southwest monsoon rains which normally arrive during the second half of June or first half of July and end in September or October. The scale and location of breeding differs every year, depending on the duration and nature of monsoon rains. The locusts tend to stay out of the irrigated agricultural areas of the Indus Valley except during periods of increased locust activity. Locust populations from adjacent areas in Rajasthan, India can cross back and forth along the common border during the summer. Once the monsoon rains end and vegetation dries out, locust adults will move from both countries towards the spring breeding areas in western Pakistan. Spring breeding normally occurs every year in Baluchistan, first commencing in coastal areas from west of Karachi to the Iranian border in about February or March. As temperatures warm up, locust adults will appear in the interior of Baluchistan from Turbat to Dalbandin and Nushki, including Panjgur and Kharan valleys. Locusts may also reach the remote Great Sandy Desert west of Kharan. Desert Locusts rarely move north of the Chagai Hills and Quetta except when swarms form. Cold weather in the interior can delay locust maturation by several weeks or more. The breeding areas continue into adjacent coastal and interior areas of southwest Iran. Breeding in Baluchistan differs from year to year depending on the timing, location and duration of the seasonal rains. In most years, spring rains will end in about April but ecological conditions may remain favorable until June. In other years, insufficient rains fall to allow breeding. The Lasbela and Uthal area west of Karachi is considered as a transition zone where locusts may be present nearly any time of year.
The Department of Plant Protection at the Ministry of National Food Security and Research is responsible for Desert Locust survey and control operations in Pakistan. Ground surveys are carried out regularly in the summer and spring breeding areas from about June to November and February to May, respectively. Surveys are usually organized from permanent locust outposts in the summer and spring areas. During emergencies, seasonal outposts are established. Pakistan is the only Desert Locust country that maintains its own fleet of aircraft dedicated for locust survey and control operations. Pakistan also hosts the oldest continually operating locust outpost in the recession area on the Baluchistan coast in Pasni. Both of these date from the pre-partition British colonial period.
The desert locust fly during day time and settle during the night and the migration activity usually does not cause damage since the locusts are not in search of food. Locusts are short horned grass hoppers. Desert locusts of Africa and Asia are normally solitary, but spring rains trigger a behavioral transformation that can results in a swarms of locust. A single swarm ranges from 100,000 to 1 billion locusts. The last time the metropolis suffered from a locust attack was in 1961. During the 1988 desert locust plague, swarms crossed the Atlantic from Mauritania to the Caribbean, flying 5 000 kilometers in 10 days. Locusts are related to grasshoppers and the two insects look similar. However, locust behavior can be something else entirely. Locusts are sometimes solitary insects with lifestyles much like grasshoppers. But locusts have another behavioral phase called the gregarious phase. When environmental conditions produce many green plants and promote breeding, locusts can congregate into thick, mobile, ravenous swarms. On one hand the locusts destroy crops and rest of the flora on the other hand they are a good source of food in many countries.

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