March 8, 2003

WHILE discussing biodiversity in Pakistan, one is amazed to observe that this country possesses immense wealth of the fauna and flora, those specific to this region and the ones that visit its lakes, forests and deserts.

The Indus delta, the Arabian Sea, and the Thar desert are the most important biodiversity-rich areas in the south of Pakistan. Many rare and endemic species of wildlife, particularly reptiles and birds, are found here. What’s common among them is that they are predators of insects specially the locust and grasshoppers.

Rosy starling bird (Sturnus resesus), locally known as “wahyo” in Sindhi and “telyar” in Punjabi, is known to gather in flocks of several hundred to feed on locusts and grasshoppers when they become abundant.

It needs to be pointed out here that wildlife predation acts as a preventive factor to locust outbreak rather than a means of quick reduction after a buildup to high pest densities.

The Federal Plant Protection Department Entomologist Mr Mumtaz Ali Khan has observed huge flocks of rosy starling in Mekran during one winter, feeding exclusively on locust hoppers. He was convinced that their activity helped to control locust swarms.

Besides birds and reptiles, there are many invertebrate desert fauna too which predate upon hoppers and adults of locust. Some beetles have also been found predating upon hoppers. The larvae of Trax procerus has been found predating upon eggs of locust.

Unfortunately, while exploiting natural resources or undertaking anti-locust campaigns in the desert breeding areas which spread over 310,799sq km, no efforts have been made, or precautions undertaken, to protect the biodiversity and the ecosystem of the desert.

Among the desert fauna the desert locust (Schistocerca gregaria) is recognized as a threat to agriculture production in Africa and south west Asia for thousands of years. Locust scourges are referred to in the Bible as well the Qur’an. A published account of locust invasion in North Africa date back to about AD811.

It is known that desert locust plagues have occurred sporadically till the present times. Normally the desert locust (Family: Acrididae-Orthoptera) is a solitary insect that occur in dedert and scrub region of northern Africa, the Sahel (region including the countries of Burkina Faso, Chad, Mali, Mauritania, and Niger), the Arabian Peninsula (comprising Saudi Arabia, Yemen and Oman), and the south-west Asia (India, Pakistan, Iran and Afghanistan).

During the solitary phase locust populations are low and present no economic threat. However, after a period of drought when vegetation flushes occur following monsoon rains in major locust breeding areas (Pakistan India border, for instance) rapid population buildup and competition for food occasionally results in a transformation from solitary behaviour to gregarious behaviour on a regional scale. Following this transformation, locusts often form dense bands of flightless nymphs and swarms of winged adults that can devastate agricultural areas. A single swarm of locust can be relatively small (spread over about hundreds of square meters) or huge (billion of locusts, with up to 80 million per square kilometre spread over an area of more than 1000sq km.

A swarm of locusts can fly 100km in the general direction of prevailing winds. Band of nymphs can march about 1.5km per day. Desert locust can consume the approximate equivalent of their body mass each day (2g) in green vegetation, leaves, flower, bark, stem, fruit and seed. Normally all crops and non crop plants are at risk. Ravages of locust could be gauged from that fact that in 1954-55 Morocco lost over $50 million (in 1954-55 Morocco lost over $50 million to desert locust in just six weeks in Sousee vally alone. In 1958 Ethiopia lost 167000 tons of grain enough to feed a million people for a year.

According to the Federal Department of Plant Protection Pakistan has encountered many serious locust invasion from time to time viz during 150-54, 1960-63, 1970-71, 1972-73, 1974-75, 1977-78, 1983, and 1993-94. In 1978 the country was faced with one of the worst locust invasion. However, the department was able to control the locust menace with help of Pakistan Army. Inspite of the fact that locust was not given chance to inflict any crop damage particularly in the green cultivated belts but in terms of money expenditure incurred during 1978 campaign was huge. During campaign 12 aircrafts, 85 vehicles and 755 workers were deployed. Aircrafts sprayed about six lakh acres with 929 sorties and 35000 tons of pesticides consumed. a total expenditure of Rs50 million was incurred. Were it would be proper to mention to control the locust invasion long persistan and highly toxic pesticides were used (BHC, Aldrin, Dieldrin, etc) which now stand band in the country as well as many parts of that world.

Considering desert locust as an international pest, the Food and Agricultural Organization (FAO) has established several commissions depending upon the geographical position of the affected countries. The South West Asia Commission is working for Afghanistan, Iran, India and Pakistan.

Reportedly (Dawn, Dec 17, 2002), the 23rd session of the Commission for Controlling the Desert Locust in South West Asia was held at Islamabad during December last. During the five-day session (Dec 16-20 ), improvement to desert locust survey, monitoring locust through elocust, Rameses and Spot satellite images were discussed.

One important development taking place in the discipline of desert locust control in Australia was described by the Director of the Plague Locus Commission Australia Dr Graeme Hamilton who was attending the session as FAO observer.

According to Dr Hamilton, in a 30,000-hectare trial, 90 per cent of locusts targetted with a biological pesticide (Metharhizium fungus) were destroyed during locust outbreak of 2001 in Australia. Insect mortality due to fungal infection has been ascribed to destruction of insect tissues, the release of toxins, and nutritional deficiencies. Here it would be proper to mention that many people around the world are looking at the potential of fungal disease of insect to agriculture and forestry pest. Successes have been made in Brazil, China and CIS countries and commercial products are now appearing in Europe and USA.

According to Dr Hamilton the fungus metarhizium anisopliae can be applied both as EC as well as ULV sprays. It is non-toxic to fish and can be used against many species of grasshoppers besides desert locust.

The advantages of controlling desert locust with biological pesticide are clear.

1. Biological pesticides are used in place of of the harmful chemical pesticides.

2. They are harmelss to biodiversity and the ecosystem.

3. Natural enemies are re-established.

4. Less contamination of environment and fewer health hazard can be expected.

Saving the ecosystem: Since the control of locusts with toxic conventional pesticides is detrimental to the desert ecosystem and their biodiversity, it is imperative that Locust Division of the Plant Protection Department Government of Pakistan endeavour to start controlling desert locust with biological pesticide as it has been done in Australia.

It is also suggested that besides desert locust, metarhizium fungus trial may also be initiated against rice grasshoppers so that its occasional outbreak particularly in the rice growing belt of Nasirabad Division of Balochistan and districts Jacobabad, Shikarpur and Larkana of the upper Sindh could be handled using spray aircrafts of the department without inflicting the fish farming industry in the rice belts of Sindh and Balochistan.

The writer is an entomologist, and a freelance contributor

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