Weapon of choice against East Africa locusts a poisoned chalice

Tuesday March 21 2023
A man sprays a locust hatch site

A man sprays a locust hatch site near Kenya’s Isiolo town in February 25, 2020. PHOTO | TONY KARUMBA | AFP


After the locusts, death. That best explains the scenes that remained after recent anti-locust spraying campaigns in the east Africa region. Birds, beetles, bees name them and you were likely to find them covering tracts of land, or so report researchers in a study.

The study says millions of litres of “poisonous insecticides”, classified as organophosphorus, and pyrethroid pesticides, were delivered to the region and used at the height of the locust invasion.

A scientific panel comprising scientists at TMG Research in Berlin-Germany has also suggested that the pesticides may have poisoned other soil-dwelling creatures and beneficial insects and leaked into water systems, posing further danger to the ecosystem.

Need for change

Their paper Insecticide use against desert locust in the Horn of Africa 2019–2021 reveals a pressing need for change. Published on March 10 in Agronomy, the paper questions the decision by states to authorise use of these compounds over safer interventions, such as were used by Somalia. 

More than 1.6 million hectares were treated with broad-spectrum organophosphate and pyrethroid insecticides in Ethiopia and Kenya at the height of the 2019–2021 desert locust infestation in the Horn of Africa.


Read: US lawmakers introduce anti-desert locust laws

Even though non-toxic biological alternatives that kill locusts but do no other harm have been available for decades, deadly chemical pesticides remained the weapon of choice, accounting for 90 percent of the spraying in the region.

Although countries such as Uganda, South Sudan, Djibouti, Eritrea, and Sudan were affected by the locusts, the study focused on Ethiopia, Kenya and Somalia.

Heavy chemical overdosing

The study done with the financial support of the German Federal Ministry for Economic Cooperation and Development, paints a grim picture, with data showing incidents of heavy chemical overdosing.

In Kenya, the study found insecticides of choice included deltamethrin (toxic to bees, insects and fish, though much less so to mammals) and fenitrothion while Ethiopia used chlorpyrifos and malathion, both organophosphates. Malathion, the most used product, followed by chlorpyrifos are considered probable human carcinogens.

Many of these pesticides are no longer used in developed countries because they have persisted in the environment for many years.

Read: Millions in Greater Horn face hunger due to locusts

Somalia was the only country that reached for insect growth regulators IGR teflubenzuron and metarhizium acridum — an environmentally friendly and viable biological alternative recommended for locusts by the Pesticide Referee Group (PRG) to replace chemical pesticides for locust control. PRG advises FAO – which the paper says supplied the pesticides and co-ordinated the spraying exercises – on the efficacy and environmental impact of different pesticides for locust control.

Environmental monitoring

The scientists bemoaned “largely absent environmental monitoring”, noting that the full extent of the impact of the organophosphates will be known after assessments into the control campaign are done and released to the public.

“Systematic environmental impact monitoring did not take place during the recent campaign against the desert locust although the toxicity to pollinators and other non-target organisms of organophosphates has been known for decades,” Dr Elena Lazutkaitė, an interdisciplinary researcher focusing on agriculture, environmental sustainability, pest control, and governance, told The EastAfrican.

“While monitoring teams in Ethiopia and Kenya observed some side effects especially on honeybees, they were largely unable to grasp the utter magnitude of the potential environmental impact. Unfortunately, these reports lack scientific rigour,” said Dr Lazutkaitė.

Regulated chemicals

According to Dr Lazutkaitė, chlorpyrifos is not only banned in the EU and US but it is also proposed to be listed as Persistent Organic Pollutant (POPs) on the Stockholm Convention among chemicals regulated to protect human health and the environment.

POPs are listed due to their mutagenic, teratogenic (capacity to cause congenital disorders in a developing embryo or fetus), or carcinogenic characteristics and resistance to degradation when released into the environment.

“Regrettably, the donor community, which includes the EU, has financed the bulk of broad-spectrum insecticide provisions through FAO,” said Dr Lazutkaitė.

Read: Banned toxic pesticides being sold in Global South

In Ethiopia, the dominant control agents chlorpyrifos and malathion applications coincided with a honey production decline of 78 percent in 2020. The two chemicals pose the highest risk to honeybees. Here, treatments went on non-stop for 24 consecutive months.

“No month was pesticide-free for two years, including during flowering times and honey harvesting times,” noted the paper.

Honey production

Ethiopia is the largest natural honey producer in Africa and ranks among the top 10 producing countries in the world. From 2010 to 2018 national honey production was growing at an average of four percent per annum, but in 2019 and 2020, honey production fell by a combined 46 million tonnes (78 percent), constituting an estimated loss of $305 million in revenue.

In another documented case in Kenya’s northern county of Samburu, a ground control team is said to have sprayed 34 times the recommended dose of pesticide on a patch of ground, killing bees and beetles while spilling pesticide on themselves and crops.

“…the lack of precautionary measures and mishandling of hazardous pesticides… for example, on the three sites treated with fenitrothion that were monitored in Kenya, there was overdosing of the product, with a concentration of 960 grammes per litre which immediately predisposed the control operations to gross overdosing, and led to non-target mortality, including birds and honeybees,” remarked Dr Lazutkaitė.

Read: Scientists use wasp to kill pawpaw pest

One of the sites in Kitui County, consisting of low-lying farm fields and grazing areas with settlements, was treated with fenitrothion on with a vehicle-mounted sprayer. Death of birds involving white-browed sparrow weavers and the red and yellow barbet, was observed in one locality within the sprayed area, but no information was provided on the methodology applied and if any systematic searches were carried out.

Thorough field searches

“Furthermore, to quantify bird mortality, an inevitability from such high dose rates of fenitrothion, thorough field searches during several days following sprays are needed. Birds affected by anticholinesterase poisoning rapidly become debilitated and seek shelter on the ground as they are unable to fly. From the monitoring reports, it is not clear how this was dealt with in the field,” they said.

In April 2020, television station NTV Kenya carried video footage showing dead and debilitated superb starling bird, Fischer’s starling and wattled starling, reportedly affected by a spray of carbosulfan in Marsabit.

Wattled starlings are considered typical “locust birds” and may have been gorge-feeding on the poisoned locusts.

All uses of carbosulfan were banned in April 2015 in 13 West-African countries based on high toxicity for birds and human health concerns.

As per the PRG locust insecticides’ outline, fenitrothion, chlorpyrifos and fipronil pose the greatest risks to gorge-feeding birds.

Lost whole colonies

Beekeepers in East Samburu County reported in 2020 to have lost whole colonies following ground treatments with 81 times over the recommended quantities of fenitrothion. This resulted in heavy bee mortality with 1,296 dead bees counted in the four hives that were inspected in Samburu County. In Kitui and Makueni Counties too.

In two districts in Ethiopia in South Omo Zone (Male and Hamer), 1,329 hives were found empty following mass deaths after the use of chlorpyrifos and malathion. Similar cases were reported in Eastern Haraghei, Oromia.

“Conversely, the use of metarhizium on nearly 253,000ha in Somalia, against both hopper bands and swarms was the most economically feasible (cheapest) control agent and demonstrates that the persistent and pervasive use of organophosphate insecticides can no longer be justified,” said the scientists, who suggested that future procurement of organophosphate insecticides and possibly insect growth regulators could become increasingly problematic due to restrictions enacted by the EU.

Cheaper alternative

It is said an important factor that informed the decision to use metarhizium in Somalia was a large number of agro-pastoralists as well as beekeeping.

The large-scale introduction of metarhizium for desert locust control, according to the team, has been hampered by perceived higher costs, a lack of trust in their efficacy and speed of action yet the cost of procured chemical insecticides ranged from $10-$30/ha treated while metarhizium cost $15.75/ha treated.

It is recommended that the complementary impact of metarhizium and bird predation on locusts should be considered in an integrated management approach for both swarm and hopper control.

“Climate change could increase the frequency and intensity of locust outbreaks. We could see new breeding grounds and new frontline countries. The status quo of deploying toxic chemical campaigns is no longer tenable,” said Dr Lazutkaitė.

Environmental devastation

Scientists are worried that these grim findings are just the tip of the iceberg of the environmental devastation that may have been occasioned by the chemicals.

Now the scientists want states to invest in smarter (AI-driven) early warning systems, and take swift action once breeding grounds are detected, even as they pursue a ban on organophosphates while simultaneously promoting biopesticides and other sustainable options.

Read: Biological pesticide to fight desert locusts

The scientists explain that neurotoxic organophosphorus compounds have an immediate knockdown effect on locusts, unlike metarhizium which is slow acting and kills over days rather than hours, hence the antipathy.

Metarhizium’s best feature — that it kills only locusts — also makes it a less profitable product, giving little incentive to manufacturers to go through the costly bureaucratic process of registering it in a country until it is needed — and by then it is too late.

On the other hand, chemicals are perceived as “cheap” because environmental and human health externalities are not accounted for by authorities.