The fall army worm (Spodoptera frugiperda)

*** The fall armyworm (*Spodoptera frugiperda*) is a noctuid pest of corn (maize) native to the Americas.

Credit: GAIN Report (Adult fall armyworm)

The pest’s destructive stage is the caterpillar (larva). Seen with the naked eye, the caterpillar can be identified by a characteristic inverted (upside down) white Y lining or mark on its head capsule. It also has 3 pale/whitish stripes behind the head, running along the top of its body length, and four dark spots (warts), towards the end of its abdomen (in the 8th abdominal segment).

Credit: CABI Fall armyworm photo guide – identification

Because caterpillars of fall armyworm (*Spodoptera frugiperda*) live through various development stages, and at each instar, exhibit different colors and different feeding habits, it is very difficult for a lay farmer to identify it. However [CABI](https://www.cabi.org/) has prepared [guidelines](https://www.plantwise.org/FullTextPDF/2017/20177801116.pdf) to assist with identification. Suffice to emphasize that the fall army worm is a difficult pest to get rid of on account of several behavioral traits. Its generation time of averagely 30 days is very short, and disperses equally as fast. Each adult female can lay in its lifetime, well up to as many as 1,000 eggs. And adult moth can also fly over 100km a night, giving it a remarkable dispersal capacity. Over the course of its development, the fall army worm caterpillar goes through several stages, exhibiting at each instar, different colors and feeding characteristics. They will feed, with the exception of roots, on different parts of the host plant, depending ##### a) On the type of host crop:
For example, on maize, leaves, stems and cobs are eaten. Larvae may burrow inside stems, attack cobs and bore through the kernels. On tomato plants, the fall army worm may feed on buds and growing points, including piercing the fruits. ##### b) On the stage of development of the host crop:
For the most part, the fall army worm attacks the reproductive structures of grown plants, boring into ears of maize as well as feeding on tassels. In young plants on the other hand, it feeds within the whorls and may cut the stems of affected young plants.

Credit: GAIN Report

##### c) On the larvae’s own stage of development or age:
Young larvae notably feed deep in the whorl, and in the first two instars, feed gregariously on the underside of young leaves, skeletonizing the leaf lamina. Larger caterpillars acting as cutworms are capable of sectioning the base of maize plantlets. When leaves are fed on, the fall army worm leaves in the whorl or funnel, a “skeletonizing” or “windowing” effect, namely, a mass of holes, ragged edges and larval frass.

Credit: www.nyasatimes.com

Overall, the *Centre for Agriculture and Bioscience International* [CABI](https://www.cabi.org/isc/datasheet/29810), observes that the caterpillars (larvae) voraciously feed on leaves, on stems, and on reproductive parts of 100+ plant species, belonging to about 27 different plant families. Its preferred hosts however are plants of the Poaceae or Gramineae (grass) family. It primarily affects maize, but also other cereals such as sorghum and millet, as well as legumes such as ground nuts, cowpeas and soya beans, including some vegetables and cotton. Such a large range of host plants ensures that the fall army worm is able to remain and survive in any given environment, even during the off-season of its most preferred host. The fall army worm is obviously not only a very competitive pest, but has an aggressive capacity to colonize any given environment; its larvae feed on each other, and mature or well-developed ones can pupate inside stems of their host plants or even in garden soils. Sandy-clay and/or clay-sand soils favor fall army worm’s pupation and adult emergence. Summarily, its behavioral characteristics make it difficult for lay farmers to identify or to control

Implications for Africa

*** In Africa, the fall armyworm was first observed in Nigeria in January 2016 on maize plants in the rainforest zone of South-Western Nigeria. And was by June 2017, detected and officially confirmed in 19 Sub-Saharan countries.

Credit:Fall Armyworm Evidence Note September 2017

On evidence of its survival traits and behavioral characteristics, the fall army worm presents Africa with perhaps it gravest economic cropping threat of recent years. Suffice to note that, the fall armyworm (Spodoptera frugiperda) compared to other congeneric army worms in Africa, such as the African army worm (Spodoptera exempta), and the cotton leafworm (Spodoptera littoralis), exhibits more advanced survival characteristics. a) The behavior of congeneric afrotropical army worms is such that they first up and form dense populations out on the wild grasses, from where the older larva then migrate to invade cultivated graminaceous crops >On the contrary, adult females of Spodoptera frugiperda directly oviposit on maize. b) Again, the mandibles of most other Spodoptera species in Africa are weaker >On the contrary, mandibles of caterpillars of the fall armyworm are comparatively stronger, and are typified by serrated cutting edges, making them very effective in feeding on plants with high content of silica. c) Older larvae of fall army worm are cannibalistic and have the unique ability to one, dominate interspecific competitors by feeding on younger ones, restricting themselves to one or two larvae per whorl, and two, to also reduce intraspecific rivals in the struggle for the same resource.

The Way Forward

*** Considering its high dispersal/spreading capability (fly over 100km a night ), its large reproduction capacity (upto 1,000 eggs), nonappearance of dispause as it grows through the six instars, and its wide range of plant hosts, the fall army worm could colonize the whole of Africa much faster than can be yet determined. The majority of farmers in Africa are small holders. From the sub-Saharan where it is the most important staple cereal grown, to other parts of Africa where it is one of the leading cereals grown, over 208 million people depend on maize (Zea mays L.) for food security. In its second evidence note [Fall Armyworm: Impacts and Implications for Africa]( http://www.invasive-species.org/Uploads/InvasiveSpecies/Fall%20Armyworm%20Evidence%20Note%20September%202017.pdf), produced in September 2017, CABI observes that that the fall army worm infestation of Africa comes with far reaching impacts on maize yield and economics: national, continental, household and even trade. This makes it an issue of continental urgency, much less because in Africa is found the majority of the critical factors conducive for the pests survival There is therefore, no doubt, an urgent need for Africa to embark on farmer sensitization, to intensify reserch into the army fall worm’s ecology and behaviour, including plant host resistance as well as the viability of natural predators as first options visavis pesticide use, among other environmnet sensitive and sustainable control methods

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