A surveillance programme for fall armyworm (Spodoptera frugiperda) is currently underway and pheromone traps were placed in six provinces (Limpopo, North West, Northern Cape, Free State, KwaZulu-Natal and Mpumalanga). During May 2018, FAW was detected in all six provinces under surveillance, with significantly higher incidences in Limpopo compared to other provinces. Actual trap count averages (i.e. average number of FAW moths per trap) ranged from 13.23 in Limpopo to 0.02 in the Free State where only one positive identification was made. The second highest number of positive identifications were made from KwaZulu-Natal (trap count average 5.33). During the next two months, FAW numbers are expected to decline due to lower winter temperatures.
Interestingly, very high number of false armyworm (Leucania loreyi) were caught in 90% of the traps. The high numbers detected raises concerns that the false armyworm could establish in South Africa (if it has not done so yet). Efforts to greatly reduce false armyworm numbers should be a priority.
Producers may face an additional invasion of armyworm – this time by the southern armyworm (Spodoptera eridania) – which is known to occur in south-eastern Nigeria and southern Bénin. It is unclear for how long this pest has been in Africa and if distribution is limited to the previously mentioned countries. Fortunately, the SAW males respond to the FAW pheromones used in trap catches and it is possible that SAW individuals can be identified from the current surveillance system. However, to ensure the absence of this pest in SA it will be necessary to conduct SAW-specific surveillance.
The current FAW surveillance programme is conducted by Crop Watch Africa, a specialist service provider in the field of early detection of pests and diseases. Crop Watch Africa has the capacity to expand the current surveillance systems to include tracking the spread of diseases such as maize lethal necrosis in other African countries. Adequate early detection is crucial to employing effective management strategies from when the pest or diseases enter the country to such time as it is eradicated.
Image left: The fall- and false armyworms are known to occur in South Africa while the southern armyworm has not been detected here yet.