Can Pakistan go beyond chemical pesticides for locust control?

Pakistan is facing one of its biggest threats yet from crop-ravaging locusts, which have dire consequences for the livelihoods and food security of millions of people.

In May this year, the United Nation’s Food and Agriculture Organization (FAO) predicted that, if they are not controlled, locust infestations in Pakistan could cause losses of about USD 2.6 billion in winter crops, such as wheat, and about USD 3 billion in the summer crops (Pakistan’s total GDP in 2019 was USD 284 billion). In 2019, the country had the worst plague of locusts in decades, with farmers describing large-scale devastation of crops.

Locusts usually multiply 20-fold with each generation. Travelling in swarms of between 30 million to 50 million in search of food, they can cover a distance of 150 kilometres and devour 200 tonnes of crops per day.

Mubarik Ahmed, the national coordinator for locust control at the FAO’s Karachi office, said that the swarms arrived from Yemen and East Africa via Iran. By the middle of the year, they were in all four provinces in Pakistan and rapidly breeding in 38% of cultivated land. In India, widespread breeding is underway throughout Rajasthan, where hoppers (young locusts) are forming groups and bands. More hatching is expected this month. There remains a risk that a few swarms could still arrive from northern Somalia. Control operations continue in both countries.

See: A plague of locusts

As these countries struggle to battle the growing threat from locusts, the only effective method currently employed by authorities is the mass spraying of infested areas with huge amounts of highly toxic chemical pesticides.

See: Pakistan turns locust threat into chicken feed

The Department of Plant Protection (DPP) at Pakistan’s Ministry of National Food Security and Research told The Third Pole that the government has already purchased “enough chemical pesticides” and spraying equipment. According to Tariq Khan, the technical director of the department, this includes 83 sprayers, with another 200 to be added by end-August, for ground operations. By October, the number of total aircrafts for aerial spraying will be 15. PKR 207,200,000 (USD 1.23 million) has been spent on pesticides alone, while the food security ministry has approved a three-year comprehensive project of USD 200 million to control locusts. In February, prime minister Imran Khan declared locust attacks a national emergency. To combat the threat China has so far given Pakistan 300,000 litres of Malathion ULV pesticide and 50 airblast sprayers for the cropping area since March.

But there is mounting pressure from environmentalists to switch to environmental-friendly solutions. One of the sprays widely used in the desert regions of Tharparkar, Nara and Cholistan is malathion, which is moderately toxic for birds and highly toxic to aquatic invertebrates, amphibians and honey bees.

Abdul Rehman is an entomologist and deputy director at the Centre for Agriculture and Bioscience International’s (CABI) Pakistan office in Rawalpindi. CABI focuses on solving agricultural and environmental issues around the developing world. While “in an emergency, the use of synthetic insecticide is unlikely to change”, said Abdul Rehman, there is a need for “sustainable, indigenous solutions” to “nip the evil in the bud”.

Nature’s tools

The first step towards this is “improved knowledge of the pest’s biology, ecology and more efficient monitoring techniques” said Abdul Rehman.

Riffat Sultana, a locust expert and researcher working at Jamshoro University’s entomology lab, offered the “life controlled by life” solution where parasitoids, both fungi and worms, annihilate locusts in embryonic, hopper and even adult stages. She said that while it is a permanent solution, it is also “slow and time consuming”.

Abdul Rehman said such insects can be reared in labs and then released in locust-hit areas.

Research carried out by CABI in 1974 listed nearly two-dozen natural enemies of locusts that devour them, he said. For Pakistan, he suggested the construction of a minimum of two labs, one in the winter breeding area of Balochistan, the other in the summer breeding part of Sindh.

In 2006, CABI successfully demonstrated control of agricultural pests like fruit flies for guava and mango; in 2011 on mealybugs for cotton in Punjab and Sindh provinces; and in 2018 for mealybugs in papaya in coastal areas of Sindh. Currently, the centre is working with the government of Sindh for the control of 11 pests that affect five crops in five districts of Sindh.

Future is biopesticides

Another possible solution is the use of biopesticides made from fungi.

But Tariq Khan said this has limitations. For example, the popular insecticide metharizium acridum lost its efficacy in high temperatures and Khan doubted it would work in the desert of Tharparkar. “Biopesticide can be a supplement but cannot be relied upon solely in plague-like situations,” he said.

Abdul Rehman, on the other hand, said the same agent was in use in Egypt’s desert and proved effective. “The locusts can be sprayed in the middle of the night or just before sunrise when temperatures drop drastically,” he said.

Khan also said it took between 17 and 21 days for a locust to die from bio-pesticide compared with instant death from chemical sprays.

Not all may die, but compete eradication was never the idea. Instead the aim is “just to bring it to a certain level that is a win-win for humans and locusts”, said Abdul Rehman. The problem was not locusts per se, but locusts in far greater numbers than the ecosystem can cope with.

The future is bio-friendly

There is little doubt in the minds of locust experts that the biological control and use of biopesticide is the route that needs to be taken in the future.

But the country has to “come out of the corrective phase and reduce the locust population substantially”, said the FAO’s Ahmed.

Further, each pesticide needs to be tested extensively under variable conditions before its full-scale application. “We cannot just buy bio-pesticide from any country and start spraying; it requires lab testing and field evaluations,” he said.

The good news is all the work has begun. The DPP has nominated provincial coordinators to test the efficacy of metarizium acridum and other potential entomopathogenic fungi against desert locusts in Pakistan.

Sultana, one of the four coordinators, is running trials for an Australian biopesticide. She said it is also important that farmers are engaged and educated about “biocontrol agents”.

The switch from synthetic pesticides to more natural solutions has also been explored in a study published in the Annual Review of Entomology. It notes that “growing awareness of the environmental issues associated with acridid control as well as the high costs of emergency control are expanding the demand for biological control” and that “preventive, integrated control strategies with early interventions will reduce the financial and environmental costs associated with large-scale plague treatments”.

It mentions the development of “effective oil formulations of metarhizium anisopliae spores in Africa, Australia, and Brazil” which open new possibilities for environmentally safe control operations.

Scientists at the International Centre of Insect Physiology and Ecology (ICIPE) in Nairobi this year also said they are experimenting with biopesticides as they look for environmentally-friendly extermination methods. ICIPE researchers were a part of a group that discovered metarizium acridum could kill locusts without harming other creatures. The method is now being used across East Africa.

Where are the locusts headed now?

As Pakistan braces for swarms from Africa with all the paraphernalia needed for a head-on collision as predicted by the FAO last month, the danger seems to be reduced.

“It seems there is vegetation in Somalia for the African locusts to remain there, and the predicted rains in Somalia from July till September will further keep the locusts engaged in that region,” said Ahmed, indicating that the threat is not urgent at this stage.