FAW moths are strong flyers with the ability to readily migrate across borders using the prevailing wind direction to aid their flights. Due to its inability to enter into diapause, the pest has adapted to migrating long distances of up to 2,000 km in its lifetime from South and Central America into North America in its migration search for food sources (Luginbill 1928). Long distance migrations are now known to occur in southern Africa and into South Africa. For example, FAW moths have been collected in pheromone traps in the Western Cape Province that are situated many hundreds of kilometres from known FAW outbreak source areas. In many of the traditional outbreak areas in South and Central America, the FAW has been reported to destroy crop fields if not effectively managed. FAW is estimated to cause annual losses of approximately US $600 million (R9 billion) in these areas (Day 2017). Many plant species are able to tolerate moderate herbivore damage, or may be able to repel attack by producing tannins and other alkaloid compounds to deter feeding. However, if the FAW late instar larvae attack the whorl of the maize plants altering resource reallocation and regrowth (Eickhoff et al. 2008), the plant will not recover from such damage resulting in total yield loss.
Fall armyworm damage to young maize plants. Photo: D. Visser, ARC-VOP, Roodeplaat.
Socio-economic impact on smallholder farmers
FAW is now known as a new invasive pest that has rapidly invaded conventional open-pollinated maize and sweetcorn fields on the African continent causing a serious concern regarding its impact on grain production and local food security, especially in smallholder and subsistence farming systems which are dominant throughout much of Africa south of the Sahara. Initial studies in South Africa have shown that the FAW attacks can have a devastating socio-economic impact on smallholder maize farmers.
The ARC-PHP has recently completed a project funded by DALRRD on the socio-economic impact of FAW in Limpopo Province. The findings of the community participation questionnaire surveys amongst the smallholder farms highlighted the direct and often devastating socio-economic impact that the FAW invasions have had in the Limpopo Province. The FAW impacted an estimated 3 500 smallholder farmers on approximately 40 000ha of land. The ARC interviewed over 300 of these farmers and found that average farm sizes were tiny, with 77% of farmers planting their homestead maize on <1ha of land, with only 3.5% farming on large farms of >100ha. Most farmers planted their maize year-round for the roasted mealie-cob vendor market, but virtually all farmers planted the conventional open-pollinated maize varieties for this cob vendor market that are also extremely vulnerable to FAW attack. Crop losses ranged from 25-100% and many farmers had to replant their maize crop more than once during the season, which severely depleted their financial resources. Most farmers relied on the Provincial Department of Agriculture to provide at least some inputs to enable them to plant, such as ploughing services and pesticides. However, the continued year-round attacks from FAW were finically crippling for many farmers, with direct impact on homestead food security and income. Most farmers had few skills or resources to plant alternative crops instead of maize and once their maize crops had been devastated they had no option but to sell livestock and household goods to earn income. Some farmers had to seek employment on other farms or even leave their communities and travel to the cities to look for work. The stark reality facing many smallholder maize farmers is that the continued FAW pest pressure may force many of these farmers to give up farming entirely, which will have far-reaching implications for these rural communities in future.
Population dynamics of FAW in South Africa
In South Africa, there is now research information available on the population dynamics of FAW, the suitable temperature range required for development in the field, as well as the overwintering survival strategies of the pest. However, it is important to continue to investigate the ecology and population dynamics of FAW in order to effectively develop management recommendations to combat this pest.
Fall armyworm caterpillars and moths on maize plants. Photo: D. Visser, ARC-VOP, Roodeplaat.
The pest has now been recorded in all provinces of the country and becomes very widespread by the end of summer. FAW populations successfully overwintered on maize in the warmer areas of South Africa during the winters of 2018, 2019 and 2020. The outbreaks pose a significant threat to food security of conventional maize (non GM maize) in smallholder rural communities who rely on maize production for homestead food security and income. FAW also poses a serious economic threat to commercial production of maize and sorghum in South Africa (Grain SA, 2016).