Occurrence of Fall Armyworm in South Africa and possible control measures and registered products

Contributing Author: Chris Coetzee

Chris Coetzee is a research agriculturist with BioScience Research in South Africa. BioScience Research is a leading OECD GLP accredited Contract Research Organization responsible for the development of crop protection products and registrations in the Southern African Region. 

 

The Fall Armyworm (Spodoptera frugiperda, Lepidoptera: Noctuidae) is a major agricultural pest that is indigenous to the Americas (1). It is widely regarded as a major pest as it attacks more than 80 different crop types, preferring graminaceous and grain crops but also attacking cabbage, beet, cotton, tomato, potato and onions amongst others (2). It was first reported present on the African continent in January of 2016 when found in South-Western Nigeria (3).  Since August 2017, 28 African countries have confirmed the presence of Fall Armyworm within their plantations, including South Africa (2). 
 

On 3 February 2017 the South African Department of Agriculture, Forestry and Fisheries issued a media statement with regards to the outbreak of Spodoptera frugiperda (Fall Armyworm) in South Africa (4). The pest was identified by the Agricultural Research Council from samples collected from the Limpopo Province which is to the North of South Africa. The pest is regarded as a quarantine pest in South Africa and carries an A1 phytosanitary status according to the European and Mediterranean Plant Protection Organisation (EPPO) (5). To date the pest has spread over much of South Africa and it is also now present in the Western Cape Province towards the South of South Africa where it presented in sweet corn during the latter part of March 2019 (6). This indicates that the pest has huge potential to spread quickly. Various scouting and management tools have been developed (5) to assist with monitoring and reporting the spread of the pest. An integrated management protocol was issued by the FAO and is available via this link: https://reliefweb.int/sites/reliefweb.int/files/resources/i8665en.pdf

 

Under ideal warmer conditions (about 28°C), the entire life cycle of the Fall Armyworm can be completed in approximately 30 days. This extends to approximately 60-90 days when conditions are colder. The moth does not exhibit diapause during these colder periods (a period of biological inactivity), so infestations can occur year-round. The entire lifecycle consists of an egg, larval, pupal and adult stage (7).

 

Eggs are laid nocturnally. The eggs are dome-like in shape, with a distinctly flattened base and a broadly round tip. Eggs are approximately 0.4 mm wide and 0.3 mm in height. The total eggs laid per event varies, but usually eggs are laid in masses of 100 to 200 eggs. Each female averages a total of 1500 eggs per lifetime, with exceptional occurrences of over 2000 eggs from individual females (7).
 

 

The Fall Armyworm exhibits 6 instars throughout larval development. The first instar larvae emerge from the eggs and often devour the egg casings. These are typically greenish in colour with distinct black heads. By the third instar, larvae deepen in colour exhibiting a brown dorsal side and distinct white lateral lines. Throughout the fourth to sixth instars, the larvae heads turn brown with speckles of white, and often exhibit a distinct inverted white “Y” shape (7). The most distinct characteristic feature of Fall Armyworm larvae is the 4 large spots that form a near-perfect square on the dorsal side of the last segment of the caterpillar’s body. The entire larval stage may take approximately 14 days in ideal warmer conditions, and up to 30 days in colder months (7).
 

 

The Fall Armyworm typically pupates within the top 2-8 cm of the soil. The larvae spin cocoons from soil particles and silk. The cocoons are oval and approximately 20-30 mm long. The pupae are generally brown in appearance, approximately 14-18 mm long and 4-5 mm wide. The entire pupal stage can occur within 9 days during summer, but can extend to 20-30 days if conditions are colder (7).
 

 

The adult moths have wingspans of approximately 32-40mm. Male moths typically have brown to grey wings with distinct white spots on the tip and centre of each wing. Females tend to be less distinct, with brownish-grey colouration. The hind wings are typically iridescent, whitish and bordered by a dark band. Adults are fully nocturnal and exceptional fliers, capable of flying 500 km before laying eggs. If winds are prevalent, distances of up to 1600km can be covered before eggs are laid. Adults tend to live about 10 days, but can live for anytime between 7-21 days (7).

 

In South Africa the following insecticidal active substances, known for their efficacy against Lepidoptera, are currently being considered for registration (Prepared by A. Huysamer).
 

Active ingredient	Crop or use
(Z)-11-hexadecenyl acetate + (Z)-7-dodecen-1-yl acetate [syn. (Z)-7-dodecenyl acetate] + (Z)-9-dodecenyl acetate + (Z)-9-tetradecen-1-yl acetate [syn. (Z)-9-tetradecenyl acetate]	Pheromone for crops and orchards.
(Z)-11-hexadecenyl acetate + (Z)-9-dodecenyl acetate + (Z)-9-tetradecen-1-yl acetate [syn. (Z)-9-tetradecenyl acetate]	Pheromone for Barley, Buckwheat, Durum, Maize, Millet, Oats, Rice, Rye, Sorghum, Sweetcorn, Triticale, Wheat
acetamiprid + novaluron	Baby marrows (syn. Courgettes, Zucchini), Broccoli, Brussels sprouts, Butternuts, Cabbage, Canola, Cauliflower, Cucumbers, Lucerne (syn. Alfalfa), Melons, Musk melons (syn. Cantaloupe, Melon), Potatoes, Pumpkins, Squashes, Watermelons, Wheat
Bacillus thuringiensis	Biocontrol agent for Maize and Sweetcorn.
Beauveria bassiana	Biocontrol agent for Barley, Broccoli, Brussels sprouts, Cabbage, Cauliflower, Maize, Sorghum, Soya beans, Sweetcorn, Tomatoes, Wheat.
benfuracarb + fenvalerate	Maize, Sorghum, Sweetcorn.
carbosulfan	Maize, Sorghum, Sweetcorn.
chlorantraniliprole	Maize, Potatoes, Sorghum, Sweetcorn.
chlorantraniliprole + lambda-cyhalothrin	Aubergines (syn. Brinjals, Eggplants), Baby marrows (syn. Courgettes, Zucchini), Barley, Beans - Chickpeas, Beans - Dry beans, Beans - Green beans, Broccoli, Brussels sprouts, Butternuts, Cabbage, Canola, Cassava, Cauliflower, Cucumbers, Gherkins, Ginger, Groundnuts (syn. Peanuts), Lentils, Lettuce, Maize, Marrows, Melons, Musk melons (syn. Cantaloupe, Melon), Peas, Peppers, Peppers - Bell peppers, Peppers - Chillies, Peppers - Green peppers, Peppers - Pimento, Peppers - Piquant, Peppers - Sweet peppers, Pumpkins, Sorghum, Soya beans, Squashes, Sunflowers, Sweet potatoes, Sweetcorn, Watermelons and Wheat.
chlorpyrifos	Maize/Corn
chlorpyrifos + cypermethrin	Maize, Sorghum and Wheat.
emamectin benzoate	Barley, Canola, Maize, Potatoes, Soya beans, Sweetcorn and Wheat.
flubendiamide	Endives, Lettuce, Maize and Spinach.
indoxacarb	Cotton, Lettuce, Maize, Peppers, Potatoes, Sorghum, Soya beans, Sugarcane and Sweetcorn.
indoxacarb + novaluron	Maize and Sweetcorn.
lufenuron	Barley, Beans, Beans - Dry beans, Beans - Green beans, Broccoli, Brussels sprouts, Cabbage, Cauliflower, Groundnuts (syn. Peanuts), Legumes, Maize, Peas, Sorghum, Soya beans, Sunflowers, Sweetcorn and Wheat.
mercaptothion [syn. malathion]	Broccoli, Brussels sprouts, Cabbage, Cauliflower, Grazing, Maize, Sorghum and Wheat.
Methomyl	Maize/Corn
methoxyfenozide + spinetoram	Broccoli, Brussels sprouts, Cabbage, Cauliflower, Maize, Sorghum and Sweetcorn.
Profenofos	Cotton and Potatoes.
pyridalyl dichloropropene-derivitive	Maize and Sweetcorn.
Spinetoram	Broccoli, Brussels sprouts, Cabbage, Cauliflower, Maize, Sorghum and Sweetcorn.
Spinosad	Baby marrows (syn. Courgettes, Zucchini), Butternuts, Cucumbers, Gem squash, Gherkins, Hubbard squash, Lawns, Lettuce, Marrows, Melons, Musk melons (syn. Cantaloupe, Melon), Patty pans, Pumpkins, Spinach, Squashes, Tomatoes and Watermelon.