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Fall armyworm


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What is it?

The fall armyworm, Spodoptera frugiperda is an insect (a moth) belonging to order Lepidoptera and family Noctuidae who’s larvae (caterpillars) are highly destructive to many crops.



How important is it?

On this page, our attention is focused on Fall armyworm in Africa which is an invasive species. Fall Armyworm is considered a major problem because of its cause a severe economic loss on major food crops worldwide. Although much more data is needed one estimate by CABI (CABI 2017) estimated losses lying between US$2,481m and US$6,187m per year. FAW is particularly problematic also because it can occur on many important crops besides maize, such as sorghum, rice, and sugarcane.




How is it identified?

The damage may vary depending on the stage of the crop, insect population, and stage of larvae, etc. Though the damage can be easily identified by characteristic scrapping (caused by first and second instar larvae-Fig 1) and holes on the leaves (caused by third to sixth instar larvae- Fig 2). Sometime may cut the leaf in half, resulting in a reduction of photosynthetic leaf area (Fig 3). The damage gives the ragged appearance to the plant. The larvae are nocturnal in habit. They are active and feed only during the night. They hide in leaf whorl during the daytime.



           Fig 1: Scraping damage caused by early instar larvae

                   Fig 1: Scraping damage       


 Fig 2: Elongated holes on corn leaves caused by late instar larvae

    Fig 2: Elongated holes     


     Fig 3: Ragged appearance of plants due to late instar larvae

        Fig 3: Ragged appearance          


            Fig 4: Late instar larvae feeding on cob

                Fig 4: Cob damage 

      Fig 5: Injury to corn plant at whorl stage

               Fig 5: Whorl injury  

What else it could be?

Plant parts

Fall armyworm (FAW)

African armyworm (AAW)

Corn earworm (CEW)

Western bean cutworm (WBC)

Common armyworm or true armyworm (AW)

African Maize Stalk Borer

Leaf whorl

Window pane symptom

Window pane symptom




Window pane symptom


Elongated holes

Starting at the margins and moving inwards, leaving the leaves with a ragged appearance



Larvae initially skeletonize foliage, but by the third instar they eat holes in leaves and soon afterward consume entire leaves

Elongated holes







Internal feeding


Discoloration of panicle

Discoloration of panicle


Feeds on anthers


Discoloration of panicle


Boreholes on husk and feeds on developing grains

Boreholes on husk and feeds on

Boreholes on husk and feeds on silk and grain

Boreholes and feeds on silk and grain


Tunnel into maize cobs


What is the difference between Fall Armyworm and African Armyworm?

"They are closely related, but have different behaviors and ecologies. FAW rarely displays the "Armyworm" behavior of larvae massing and "marching" across fields. As a native to Africa, the African Armyworm faces complex of natural biological enemies (predators, parasitoids, diseases). The FAW probably arrived in African unaccompanied by its natural enemies allowing their populations to increase even more unchecked than normal."

What crop does it eat?

FAW has a wide host range but at present, it becomes a major problem in African continent mainly on corn, rice, sorghum, sugarcane, wheat, and millets. It also prefers to feed on cowpea, peanuts, potato, soybean, and cotton. It is considered a polyphgagous pest meaning it easts many different types of food plant. 

Is maize affected by FAW safe to eat?

"FAW mostly eats the leaves of maize. Occasionally it will infest ears as well. Usually, such ears are not consumed by humans. While direct damage from FAW doesn't affect the food safety of the maize, it could make the maize more susceptible to aflatoxin presence."

Where does it occur?

FAW  originated from tropical and subtropical regions of the Americas (North and South America). It is now a serious pest in West, Central, and Southern Africa. On this page, we will attempt to provide an update on country records. 

South Africa       

         Malawi      Angola       Niger       Benin     Sao Tome and Principe


        Ethiopia      Rwanda      Nigeria       Togo      Democratic Republic of the Congo        


        Mozambique        Burundi            South Sudan       Namibia

     Republic of the Congo 


        Zimbabwe      Cameroon      Guinea       Chad



        Botswana      Zambia      Burkina Faso             


Is the current situation going to get worse?

"The adult female moths of FAW is a strong flyer and will continue to spread across the continent, and possibly beyond. Populations of FAW may continue to build, as they find more host plants to multiply on, and in the absence of the complex of natural biological enemies (general predators like ants and earwigs, specialized parasitoids) and a host of entomopathogens (virus, bacteria and fungi)." 


Is there an impact on trade?

"Exports of crops that are host plants for FAW from African countries with confirmed presence of FAW will come under new scrutiny from importing countries that haven't reported FAW."

What is the biology of the insect?

1.  How do I recognize it?

Fras: The presence of moist sawdust-like frass near the funnel and upper leaves (Fig 6).

Larvae: Larvae undergoes six developmental stages (called instars). The first and second instar larvae are green in color with a black head (Fig 7). The third to sixth instars larvae are light tan to tan, green in color with white visible strips on the body (Fig 8). Also, these stages have distinct four dark spots arranged in a square on 8th and 9th abdominal segments (Fig 8).

Egg: Eggs are laid in masses. Each mass may contain 100 -200 eggs and covered with grayish cottony scales and tiny bristles (Fig 10).

Adult moth: Both male and female moths are 30 to 40 mm from wing tip to wing tip (Fig 11). The hind wings of both sexes are white/silver with a narrow dark brown border. The forewing of male moths is having more patterns and a distinct white spot on the outer tip.

2.  What is the life cycle?

The life cycle of FAW involves an egg, larva, pupa and adult moth (Fig 12). The main destructive stage is a larva. Generally, female moth lays 100-200 eggs in a mass on the lower surface of the leaves, but sometimes can also found on the upper surface. Eggs will hatch in 1 to 3 days. The first and second instar larvae feed on corn leaves by scraping the leaf surface. Whereas, the third to sixth instar larvae feed on leaves by making elongated holes. The larval stage lasts for 9 to 20 days, after which the mature larvae fall off and burrow into the soil and pupate inside the cocoon. Within 8 to 10 days adult moth will emerge from the pupa.

             Fig 6: Appearance of moist sawdust-like frass near the funnel and upper leaves

           Fig 6: Saw-dust like frass  

        Fig 7: Early instar larvae of fall armyworm

           Fig 7: Early instar larvae  

   Fig 8: Late instar larvae of fall armyworm

Fig 8: Late instar larvae 

             Fig 9: Distinct four dark spots arranged in a square on 8th & 9th abdominal segments 

             Fig 9: Distinct four dark spots  

        Fig 10: Egg mass of FAW on the upper surface of corn leaf 

      Fig 10: Egg mass  

   Fig 11: Adult moth of fall armyworm

Fig 11: Adult moth  

            Fig 12: Life cycle of fall  armyworm

                       Fig 12: FAW Lifecycle    

        Fig 13: A. Corn earworm (Helicoverpa armigera) larvae, B. African armyworm (Spodoptera exempta) larvae, C. Common/true armyworm (Mythimna unipuncta), D. Beet armyworm (Spodoptera exigua) larvae.

              Fig 13: Other pests of maize


3. How does the pest overwinter/overseason?

"In the tropics, breeding may be continuous with four to six generations per year, but in the northern regions only one or two generations develop; at lower temperatures, activity, and development cease, and when the gel occurs, all stages are usually killed. In the United States, S. frugiperda only spends winter in southern Texas and Florida. During mild winters, pupae can survive in more northern locations."

4. How does it spread within a crop and within/between regions?

"FAW moths generally disperse about 500 km (300 miles) before oviposition, which is sufficient to move from seasonally dry habitats to wet habitats in Central America (Johnson1987). Moths fly downwind, above the boundary layer (the lowest part of the atmosphere, above which the wind direction and strength may be different), so the direction of movement depends largely on prevailing winds. When the wind pattern is right, moths can move much larger distances: for example, 1,600 km from Mississippi to southern Canada in 30 hours has been recorded (Rose et al. 1975). Clearly, FAW has the potential to spread rapidly across Africa: at least 500 km per generation, with a suitable wind." (CABI, 2017)

How is the Fall Armyworm managed?

1. What can be done (by extension, agriculture department, the farmers, etc.)?

"There are many experiences and recommendations for managing FAW from the Americas. African farmers will need access to information and resources to sustainably manage FAW."

2. What alternative crops can farmers be advised to grow?

"Maize is the most infested now in Africa. As a staple crop, it is unlikely that farmers and their families will want to abandon maize. There are ways managing FAW in maize, as demonstrated in the Americas."

3. Can FAW be eradicated from Africa?

"Unfortunately no. The adult female moth of the Armyworm is a strong flyer and has rapidly spread across Africa, infesting crops (maize has been the most important to date) in probably millions of hectares of crops. It is far too widespread and numerous to be eliminated."

4. If the FAW is native to the Americas, aren't there experiences and practices that can be applied in Africa?

"Definitely. There is a wealth of management experience and research from the Americas that can be shared and tried in Africa. FAO is actively promoting South-South cooperation to bring this experience and knowledge to Africa."

5. How can field scouting assist management?

 Scouting can help to detect fall armyworm infestations before they cause economic damage. So survey the field regularly and look for egg mass, leaf damage, and larvae. The best time to look for larvae is early morning or late afternoon.

6. How can scouting be done in the field?

"Determine the field to be sampled. For a smallholder, this is typically less than 2 ha. If the fields were planted at different times, with different varieties, or with different conditions (intercropping, fertilization, etc), then each plot should be sampled differently.

In the field, walk a letter "W", covering the entire field:

Fig 14: Scouting for Fall Armyworm

At the start and at every turn, inspect 10 plants in a row. These ten plants are called a "station". Look carefully in the whorl of each plant for signs of recent leaf damage or fresh frass in the whorl. These indicate a live larva, probably FAW, in the whorl. Do Not include plants with some damage to older leaves, but with no clear signs of current damage. Only currently infested plants need be counted. Keep track of the number of plants currently infested in this way (in this example FAW infested plants are marked with an "X"):

Fig 15: Field scouting record example

The total of plants infested in the 50 plants counted is 6+4+4+5+7=26

So in 100 plants, it would be double 26X2 = 52, or 52 percent of the plants infested."

7. What cultural control measures can be taken? 

   - Deep summer plough might expose the pupae to sunlight or predators

   - Keep the field and surrounding area free from weeds

   - Plant early in the growing season

   - Avoid planting new crops near infested field

   - Look for egg mass and crush them by hand

   - Provide proper nutrients to plant so that they can withstand infestation

8. Can pesticide be used to control FAW?

"Pesticides may be needed to control FAW locally. The most effective, lowest-risk, economical, accessible and easily used by smallholders (without sophisticated machinery) need to be determined within each country and across the continent. It's not just a question of the most effective pesticide in a research station, the specific recommendations (active ingredient, formulation, type and timing of application), and their costs and benefits to smallholder farmers must be determined." 

9. Are there effective chemical control measures?

"In some areas, resistance to insecticides may be widespread and control can be difficult. Recommended insecticides for Spodoptera spp. include esfenvalerate, carbaryl, chlorpyrifos, malathion, permethrin, and lamba-cyhalothrin." (CABI 2017)

10. When should pesticide applications begin in maize to protect it from FAW?

"Only when justifiable. Low levels of infestation at certain stages of maize growth may not cause much yield loss. The economic or action threshold must be determined and recommended for each stage of maize growth and for each type of pesticide and application techniques. Costs can vary tremendously. To economically justify their use, the costs of pesticide use must be equal to or less than the value of the additional yield that farmers receive for taking action. The prices that farmers receive for their harvest must also be correctly valued."

11. Are aerial applications of pesticides recommended for the FAW?

"No. The destructive life stage (the larva) digs deep into the whorl of maize occasionally, making the aerial applications of very low efficacy, while spreading pesticides over large areas of non-targeted habitat."

12. How can pheromone traps be used in management?

 Traps baited with pheromones hold potential for predicting when the FAW infestations develop. So installing pheromone traps in the field help to monitor and kill the adult insects.

13. Is there a role for transgenic maize?

 One possibility is to modify maize to produce a toxin such as Bt toxin, which has proved successful in some crops like cotton and maize in the US. Fred Gould of NC State made a video (below) of possible problems will considering genetic modification as the solution to the FAW problem in Africa 

14. Is the use of biological control a possibility for the FAW in Africa?

"There are many biological organisms that can help control FAW. Some may be naturally occurring in Africa (general predators, parasitoids and some entomopathogens), and some might need to be introduced from the Americas (specialized parasitoids, predators, and certain strains of entomopathogens). The use of botanicals is also an appealing option."

15. What are the prospects for IPM? 

"An Integrated Pest Management (IPM) approach is strongly recommended. Reliance on single control methods may, in the long run, either be unsustainable or ineffective and, in the worst cases, increase the likelihood of FAW resistance."


CABI Crop Protection Compendium. (2017). Spodoptera frugiperda (fall armyworm) datasheet. Available at: https://www.cabi.org/isc/datasheet/29810. [Accessed 4 December 17]. Paid subscription required.

Zebdewos Salato, Jayne Crozier, Negussie Efa, Margaret Mulaa (2017). Fall armyworm (FAW) on maize. Pest Management Decision Guide: Green and Yellow List. https://www.plantwise.org/FullTextPDF/2017/20177800723.pdf

FAO Briefing Note on FAW (2017). http://www.fao.org/food-chain-crisis/how-we-work/plant-protection/fall-armyworm/en/