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ABSTRACT

Since its discovery in May 2018, the fall armyworm (Spodoptera frugiperda) has become the most destructive pest of maize in India. Its fast spread across India`s maize growing areas in varied agro-ecologies within a shorter period poses a significant threat to marginal maize farmers, industries and food security. Other crops, such as sorghum and millets have also been documented to have fall armyworm incidence with varying degrees of economic damage. In this article, the importance of fall armyworm, its life cycle and the level of crop damage are discussed. Management of fall armyworm is the most important aspect as its damage causes serious economic yield loss of the crop. Hence, an approach of integrated management is the most sustainable and effective way of management for fall armyworm.

Cite this article:

 

Praveen BR, Babu CRT, Rundan V, Singh M (2022) Fall armyworm: A devastating pest of maize and its management. Food and Scientific Reports, 3(8):16-18. 

1.    Introduction

                Following rice and wheat, maize (Zea mays L.) is the key tertiary crop in India in producing food for humans, feed and fodder for livestock. It also serve as a raw materials source for a plenty of products like alcoholic beverages, cosmetics, starch, protein, sweeteners and bio-fuel in industries. With 83 % of its production going to the starch and feed industries as a result, maize has become a well-known industrial crop. Indian farmers who grow maize are at risk from the invasive insect known as the fall armyworm (FAW). It is indigenous to subtropical and tropical areas in North America, where it primarily destroys maize harvests in the autumn (FAO, 2022). Early in 2016, FAW was found in Nigeria, Central and Western Africa. Then, through the state of Karnataka, it expanded to India. In May 2018, it was first found in corn fields at the COA, University of Agriculture and Horticultural Sciences, Shivamoga, Karnataka. In Karnataka, severity of the FAW damage ranged from 9 to 62%, with a yield loss of 34% (ICAR-NBAIR, Bangalore). Due to its early occurrence in the crop life cycle, heavy forage habits, violent behaviour, extreme fertility rate, rapid migration, wide variety of hosts and irreparable crop damage, FAW is a significant pest of maize.

2.    The life cycle of Fall Armyworm

The life cycle of the FAW lasts approximately thirty days (summer), sixty days (spring and autumn) and eighty to ninety days (winter).

1.       Egg: It has a dome-like shape, a flattened base and a curling upward tip at the top. The greatest number of eggs produced by a female is over 2000, but often it is between 500 and 1500. However, each egg mass will contain between 100 and 200 eggs. The female additionally covers the egg mass with a layer of grey scales, giving it a hairy or rotting appearance. The egg stage only lasts 2 to 3 days in the summer (Kandel and Poudel, 2020).

2.       Larva: The FAW has six larval instars. The larva`s head is black in the first instar and has a green colour in the second. In the third instar, lateral white lines on the body`s dorsal surface turn brown. From the fourth to the sixth instars, the head is reddish-brown with white mottling and the brownish body has white sub-dorsal and lateral lines. The dorsal surface of the body, which is typically dark in colour and bears spines, develops elevated spots. Four black spots arranged in a square pattern on the dorsal side of the penultimate abdominal segment are another distinctive characteristic. The mature FAW larva has a white inverted "Y" shaped epicranial suture, which is thought to be the most distinctive identifying feature of the genus Spodoptera. The larval stage lasts around 14 days in the summer and 30 days in the winter.

3.       Pupa: From 2 to 8 cm deep in the soil, pupation takes place. The larva connects silk and earth particles to form an oval-shaped loose cocoon. The larvae may weave leaf debris and other materials together to create a cocoon on the surface if the soil is too hard. The pupa will be reddish-brown in colour. The pupal stage lasts approximately 8 to 9 days during the summer, whereas it lasts 20 to 30 days during the winter.

4.       Adult: Forewing of male moth often has triangular white dots towards the middle and at the tip of a grey and brown colour. Female forewings are less noticeable and can be either uniformly greyish brown or mottled with light brown and grey. The hindmost wing is shining silver-white with a brief dark border on both sexes. Adults are nocturnal by nature and they are very active when the weather is warm and muggy. Typically, the female lays her eggs in the first 4 to 5 days of the life cycle. The estimated average adult life cycle is 10 days, however it can vary between 7 and 21 days depending on abiotic and biotic variables.

 

 

3.    Damaging symptoms of Fall Armyworm

 

·         Young instar only consumes leaf from one side, leaving the other side unharmed.

·         In their 2^nd or 3^rd instars, they start to chew through the edges of the leaves, creating holes.

·         Shot holes are a distinguishing line of perforation in the leaves that are produced by maize which has been fed through the whorl.

·         Older instars severely eat corn leaves, just leaving the mid ribs and petiole behind.

·         Early whorl stage damage potential is the lowest, mid whorl stage damage potential is intermediate and late whorl stage damage potential is highest.

·         Additionally, larvae will tunnel into the plant`s growing point, limiting its ability to grow.

·         On occasion, they eat the kernels of maize by digging through the ear.

 

4.    Management of Fall Armyworm

A. Preventive measures

1.       Monitoring

·         Install traps at 5 per acre rate both during crop season and during the off-season.

2.       Scouting

·         At this stage, the correct measurement should be done if 5% of the plants have damage from seedling to early whorl stage.

·         Measures must be taken if 10% of whorls in the mid and 20% of whorls in the late whorl phase have recently suffered damage.

·         Spraying chemical insecticides during the tasseling and silking stage is not recommended. In the event of cob damage, a suitable bio-pesticide can be employed.

3.       Cultural measures

·         Deep summer ploughing exposes FAW pupae to heat and rapacious birds.

·         In northern and central India, control is generally performed by exposing larvae to below-freezing temperatures by keeping them on the upper soil surface throughout the winter.

·         Plough in a weed free conditions and use fertilizers in a proportional way to get rid of the alternative hosts.

·         By creating a narrow trench around the cultivated land and filling it with insecticide and water, you can stop FAW larvae from moving from one region to another.

·         Staggered sowings and early synchronised maize sowing should be avoided in order to reduce crop availability for FAW growth and subsequent epidemics.

·         Intercropping of corn with pulses that are suited for the region (corn + pigeon pea/ black gram/ green gram).

·         Three to four row Napier as a trap crop should be sown all around the corn field and as and when the Napier starts to show signs of damage symptoms, it should be sprayed with either 1500 ppm of Azadirachtin or 5% NSKE.

·         Apply local plant extract, soil, ash, charcoal and other ITK techniques to the maize whorl.

4.       Mechanical measures

·         Hand-selected eggs and larvae are smashed or submerged in kerosene water to kill them all at once.

·         The whorls of the damaged maize plants were covered with dry sand.

·         In the first 30 days after sowing, apply sand + lime in a 9:1 ration to whorls.

5.       Traps

·         At the start of the crop, place 5 FAW pheromone traps per acre and 1 light trap per hectare.

·         Male moths were trapped using FAW-specific traps at 15 per acre rate.

B. Curative measures

1.       Biological measure

·         Intercropping with pulses, oil seeds and lovely floral plants that promote the growth of natural enemies can boost plant diversity.

·         At intervals of one week, release an egg parasitoid such as Telenomus remus or Trichogramma pretiosum at a rate of 50,000 per acre.

·         Bio pesticides: If 5% infestation level from seedling to early whorl stage and 10% in cob damage stage, fungus and bacteria like Beauveria bassiana, Nomuraea rileyi, Metarhizium anisopliae and Verticilium lecani can be used at the rate of 5g per litre on whorl of the plant.

·         Apply neem oil at 5 ml/lit or Azadirachtin 1% EC at 10000 ppm at one week after planting as an oviposition terminator.

·         Install 25-50 bird perches per hectare to entice predatory birds to feed FAW larvae in the early stages of the crop.

2.       Chemical measure

·         The effectiveness of the seed treatment with Cyantraniliprole 19.8% + Thiamethoxam 19.8% FS at 6 ml/kg of seed is 15 to 20 days.

·         Seedling through early whorl stage (first window): To prevent 5% damage from FAW larvae and reduce the hatchability of recently dropped eggs, squirt 5% NSKE or Azadirachtin 1500 ppm at 5ml/lit of water.

·         From the middle to the end of the whorl stage (second window): To manage second and third instars with more than 10% foliar damage, pesticides such as Spinetoram (11.7% SC), Chlorantraniliprole (18.5% SC), Thiamethoxam (12.6%) and Lambda Cyhalothrin (9.5% ZC) may be administered up until the early tasselling stage.

·         Poison baiting is suggested for larvae in their second window`s late instar. Rice bran at 10 kg with 2 kg of jaggery should be fermented in 2 to 3 litres of water for 24 hours. Add 100g Thiodicarb 30 minutes before field application. The plant`s whorl should receive this bait injection.

·         Early in the morning or late at night, apply all sprays with the whorl in mind (Ministry of Agriculture and Farmers Welfare, GOI).

Conclusion

Due to various traits like voracity, rapid flight ability and more than 80 different hosts, the FAW is spreading quickly in India. Due to a lack of fundamental knowledge about the insect, IPM development to manage FAW in India is still in its infancy. However, National Agricultural Research System, GOI play a positive role in raising alertness and managing FAW through Research Institutes, Network Projects and Agricultural Universities.

References

Fall armyworm: An identification guide in relation to other common caterpillars, a South African perspective, www.grainsa.co.za/upload/Fall-Armyworm-Identification-Presentation.pdf

FAO (2022). www.fao.org/fall-armyworm/en/

Kandel S and Poudel R. (2020). Fall armyworm (Spodoptera frugiperda) in maize: An emerging threat in nepal and its management. International Journal of Applied Sciences and Biotechnology, 8(3): 305-309.

Management of fall armyworm in maize, GoI, www.ppqs.gov.in/sites/default/files/faw_do.pdf

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Fall armyworm A devastating pest of maize and its management 1_compressed.pdf