Namibian farmers warned against brown locusts

Landowners and farmers in Namibia have been cautioned by the Namibia Agricultural Union to be on the lookout for outbreaks of brown locusts ( Locustana pardalina).

The organisation said in a statement that large-scale incidences of the insects were highly probable following the high rainfall so far this summer. According to the statement, chances of locust outbreaks at the end of the rainy season remained high, while large-scale outbreaks could also be expected between September 2021 and January 2022.

Dr Gerhard Verdoorn, operations and stewardship manager at CropLife South Africa, said the outbreaks that had so far occurred in South Africa, Namibia, Angola and Botswana formed part of a single complex that developed after the good rainfall in 2020/2021.

Brown locusts were able to exist in either a solitary or gregarious phase. In the latter, the insects congregated in swarms and migrated over large areas, and populations could reach plague proportions.

Locust swarms could vary in size from less than one square kilometre to several hundred square kilometres. According to the Food and Agriculture Organization of the United Nations (FAO), a single swarm could include up to 80 million adult locusts in a single square kilometre.

The insects posed a threat to food security, and the FAO announced in 2020 that it was working with the Southern African Development Community and the International Red Locust Control Organisation for Central and Southern Africa to support the governments of affected countries in the region to control locusts.

According to the South African National Biodiversity Institute, locusts in the gregarious phase were driven by desperation caused by hunger, and swarming was a response to finding new pastures for feeding. Verdoorn said outbreaks in southern Namibia’s Kalahari Desert and south of Maltahöhe could be expected before the onset of winter, should climatic conditions allow for this. Sufficient soil moisture and a minimum temperature of 31°C were required for an outbreak.

“I am, however, extremely worried about next summer. An outbreak this summer would mean that vast numbers of egg parcels would be deposited in the soil. I therefore call on farmers in the affected countries to religiously inspect bare patches on their land for egg parcels,” he said.

The female locusts deposited the egg parcels between 30mm and 50mm into the soil. When discovering egg parcels, the soil must be opened up and livestock herded over the areas where the eggs were found. Verdoorn also advised farmers to hitch a tractor tyre or two car tyres behind a bakkie and drag them across swarms that formed on roads in an effort to curb the usage of chemical products. A large tree trunk could also be used, he added.

‘I AM EXTREMELY WORRIED ABOUT [OUTBREAKS] NEXT SUMMER’