Current status of information and pest status of the invasive pest, Fall Army Worm, in South Africa
Identification of the pest
Initial identifications were done visually based on external characteristics of larvae (worms). After collection and rearing of larvae by Scientists from the ARC-GCI and North-West University, moths were delivered to Ms Vivienne Uys, an expert taxonomist at ARC-PPR for identification using classical taxonomy. Larval material was also sent to Stellenbosch University where molecular identification will be done. The identification will be confirmed by 7 February 2017.
What are the implications
We can extrapolate from current knowledge on the African army worm species, which are also more tropical like the FAW, that the FAW outbreaks in South Africa in future will most likely be sporadic. However, this is only speculation since this pest species is highly adaptive and has evolved resistance to Genetically Modified (GM) maize in the US and also to insecticides in other countries.
Short term investigations that have to be done to address the possible negative impact on South African agriculture is the evaluation of available GM Bt maize for its efficacy to kill FAW larvae and to identify effective insecticides. Research is therefore essential. Several agro-chemical companies have embarked on this process.
State of infestation (how much crops/hectares are infected)
Other crops?? We have inspected spinach and green peppers and lucerne fields in infested areas and found NO infestations on these crops.
We are not able to make an accurate estimate yet. At the moment it seems that only maize is attacked.
The areas from which reports of attacks were received are in in the Limpopo and North-West provinces. It seems the 1st observations of the presence of this pest were made during December 2016. These were quickly followed up by the scientific community and DAFF. Pest samples were collected on 20 January and a DAFF meeting on the topic was held on 25 January.
The pest infestation is limited to “hot spot” areas in regions such as Delareyville, Zeerust, the Springbok Flats, notably Bela-Bela, Settlers and Makopane area. Fields in the Brits, Koedoeskop, Thabazimbi areas are heavily infested. Sweet corn farmers in the Lowveld area Tzaneen/Hoedspruit area have serious infestations.
Are there any existing or proposed control measures?
Pesticides will have to be registered. At the DAFF meeting on 25 January it was noted that there’s currently no chemicals registered for FAW control in maize crops in South Africa. However there’s other chemicals registered for Lepidoptera including organophosphates etc. that can be recommended to farmers. Emergency authorization of use of possible chemicals from the registrar could be considered based on promulgations of the Act 36. Companies will apply for emergency registrations with the registrar of the Act.
After the DAFF meeting a list of insecticides that will most likely be effective was compiled by Dr Gerhard Verdoorn with inputs from Universities and the agrochemical industry.
Preliminary field observations indicate that GM Bt maize suppresses larval feeding and damage. This puts the pest in a different context in South Africa since countries to the north (especially Zambia and Malawi), where devastating outbreaks occurred, do not cultivate Bt maize.
The pest was introduced into African from South/North America during 2016. It is strongly suspected that the pest in South Africa is from a south-ward migration of this species from tropical Africa. Damage to maize in especially small farming systems in countries such as Zambia and Malawi. The initial reports from West Africa were made from Benin, Sao Tome and Northern Nigeria.
It will never be possible to eliminate this pest. It is an invasive species which is here to stay. Research should be conducted on its adaptability in the region and to identify areas where it will establish to become endemic.
Research is needed to develop and integrated Pest Management (IPM) strategy in order to limit pest outbreaks and improve control methods in future.