Farmers in Umguza and Bubi farming areas in the Matebeleland North province of Zimbabwe are struggling to contain a massive outbreak of quelea birds which are feasting on their crops of wheat, rice, barley, sorghum and millet, reported newzimbabwe.com on May 16th. The acting director of the migratory pest security department in the Ministry of Agriculture, Shingirai Nyamutukwa, said that the issue was reaching crisis levels.

Red-billed quelea,  Quelea quelea, are said to have the largest population of any bird species in the world, an estimated 1.8 billion across 25 countries.  The birds form enormous flocks of up to 100,000 birds which travel long distances to find food when the start of the rainy season causes seed in their preferred dry season feeding areas to germinate. 

As meteorological conditions vary from year to year, the locations and severity of quelea infestations also vary between seasons. In general, the birds breed 2 or 3 times a year, but up to 5 times per annum in East Africa, during and just after rainy seasons. Damage can also occur in dry seasons when the birds continue to flock together and may roost in very high numbers.

Controlling the birds can be done chemically but standard organophosphates are highly toxic to other organisms.   Apart from chemical avicides, the only rapid technique to reduce the numbers of quelea substantially is the use of explosives combined with fuel to create fire-bombs but these also have negative effects on the environment, can be dangerous and have associated security issues. The technique is labour intensive and in practice can only be deployed against small colonies and roosts. 

Red Billed Quelea – Wikimedia Commons

An integrated pest management (IPM) approach is the most environmentally benign strategy but, apart from when circumstances permit cultural control measures, most IPM activities only have realistic chances of succeeding in controlling quelea in small (<10 hectares) areas. For instance, mass-trapping, which also has the advantage of providing a food source, is suitable when quelea roosts and colonies are less than 5 and 10 hectares in area, respectively. 

Meanwhile in Zimbabwe farmers say they are now spending their time clanging metal objects and shouting at top of their voices in a desperate bid to save their crops, according to newzimbabwe.com(Sources: dlco-ea.orgnewzimbabwe.com)

Even more widespread and destructive than the quelea are desert locusts, Schistocerca gregaria, a regular phenomenon in east and southern Africa.  On April 8th bloomberg.com reported that South Africa was experiencing its biggest infestation of desert locusts in decades with heavy rains allowing the crop-eating insects to multiply rapidly.

Locusts feeding – Wikimedia Commons

The infestation, which started in September 2021, has spread to three provinces – the Eastern Cape, Northern Cape and Western Cape – and 80 million rand ($5.4 million) has already been spent combating it with insecticide, the agriculture department said in a statement on April 7th.   “Due to the amount of rainfall received, the outbreak tends to escalate” allowing the locusts to quickly breed, the department said. “The wind is also playing a role in migrating the swarms to the areas where” the locusts haven’t been seen before, including citrus farms in the Eastern Cape, it said.   South Africa has had an exceptionally wet rainy season. In December many districts in the country had their heaviest rain since records began in 1921. (Source: bloomberg.com)

In 2020 eastern Africa experienced a locust invasion which was described as the worst in 25 years for Ethiopia and Somalia, and the worst in 70 years for Kenya.  In February 2020, local media reported that a swarm covering 2,400 sq km (930 sq miles) was recorded in northern Kenya which could have been the largest ever recorded in Kenya. 

Desert locusts move in large numbers and can multiply in numbers by a factor of 20 every three months. This is a major cause for concern as they can destroy large areas of vegetation and crops, threatening food security and the livelihoods of affected populations. A single square kilometre swarm can eat as much food in a day as 35,000 people.  (Source: reliefweb.int)

The first line of defence is chemical insecticides, which can be distributed using packs on the ground, or by aircraft. During Covid-19, this protection was made difficult or, in some places, impossible because of disruption to the chemical supply chain. And spraying, though one of the more effective methods, can be harmful to the environment and to human health.

Alternatives include the use of drones and electrified metal grids to control swarms. Drones can be navigated to fly low enough to spray chemicals and do surveillance, without the need for larger planes with human pilots. Electric grids can be dragged over fields to generate vibrations in open fields to scare away the locusts and shock any that it comes into contact with. 

Another option is to use “biological pesticides”, based on the fungus Metarhizium acridum that infects and kills locusts. Fungus-based pesticides are thought to be harmful to a much narrower range of species than conventional pesticides, and so pose less risk to the environment and people. However, some researchers have questioned whether fungal deterrents could also harm other species of insect, such as termites. They also take longer to kill the pests than conventional pesticides, which risks greater crop damage.

But some of the key protection comes before the swarm arrives. Locust swarms usually happen when a prolonged drought is followed by heavy rains and remote weather stations help to capture data that reveals such weather variations and gives farmers time to start spraying early. (Source: www.bbc.com

A third invasive species threatening the continent’s food security, incomes and livelihoods is the fall armyworm (FAW), Spodoptera frugiperda.  The term “armyworm” can refer to several species, often describing the large-scale invasive behaviour of the species’ larval stage.  Its scientific name, frugiperda, means “lost fruit” in Latin, named because of the species’ ability to destroy crops.

The pest, first reported in Africa in 2016, is estimated to cause up to $9.4 billion in annual yield losses in Africa, according to the Food and Agriculture Organization (FAO).  The fall armyworm feeds on the leaves, stems and reproductive parts of maize and 80 other plant species in cereals and vegetables.

Fall Armyworm Caterpillar – Wikimedia Commons

In Kenya, farmers in the western part of the country have been alerted of the invasion of the destructive pests as the planting season continues. “There is a sporadic invasion of fall armyworms in maize fields and we are taking early precautions in sensitizing farmers on the need to report promptly to our extension officers,” Reuben Seroney, county director of agriculture for Uasin Gishu, told Kenya News Agency on April 18th.  Seroney said the worms have affected nearly 5,000 hectares of crops, most of it maize.

Fall armyworms have also been reported in more than 47 districts in Uganda, as well as in neighbouring Tanzania.

In a statement on April 22nd, Director-General of the FAO, Qu Dongyu, said only six African countries had reported the pest as of 2016. But since then it has spread to 78 countries in Africa, the Near East, Asia and the Pacific.  “Fall armyworm knows no boundaries and is continuing its rapid march across the globe,” Qu said.

The FAO said the spread of fall armyworm is driving intensified pesticide use, putting human and environmental health at risk.  As part of response measures, the FAO said the maize hybrids tolerant to fall armyworm are now available from the International Maize and Wheat Improvement Centre for testing and release in African countries.  The FAO has also tested integrated pest management tactics in eight geo-zones with good results.

The measures are already bearing fruit, with yield losses caused by fall armyworm having reduced to 5% and below in Burkina Faso since 2020, for example.  Additionally, biopesticides and biological control have shown up to 90% field efficacy against the pest.  However, the FAO warned that the pest continues to spread, exposing new farmers and their livelihoods.  Despite the achievements, FAO warned that integrated pest management adoption and yield loss reduction are uneven from country to country, and as use of hazardous pesticides persists. (Sources: en.wikipedia.orgglobal.chinadaily.com.cn)

For further information about the Africa Research Bulletin:

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