Fall armyworm

The adult moths are wing tip to wing tip, with a brown or gray forewing, and a white hindwing. There is slight sexual dimorphism, with males having more patterns and a distinct white spot on each of their forewings. The first larval instar is light colored with a larger dark head. As they develop through instars, they become browner with white lengthwise lines. They also develop dark spots with spines. == Geographic range ==

Native range The fall armyworm is widely distributed in eastern and central North America and in South America. It cannot survive overwinter in below freezing temperatures, so it only survives the winter in the most southern regions of the United States, namely Texas and Florida. Because of this, the fall armyworm is a more prominent pest in southeastern states. However, seasonally it will spread across the eastern United States and up to southern Canada, inhabiting areas with suitable food supplies. has been modelled using CLIMEX. The modelled global potential distribution reflects the marked seasonal range dynamics experienced in North America, with much of the potential range in Europe, South Africa, China and Australia consisting of habitat that is only climatically suitable during the warmer months.. A more recent physiologically-based population dynamics model was developed for assessing the potential distribution of S. frugiperda in Europe. The model showed that the Mediterranean coastal areas of Southern Europe might be particularly suitable for the establishment of the species. Africa S. frugiperda was first found on the African continent in 2013 in Sao Tome, It has since spread to 28 countries in Africa. Asia S. frugiperda was first detected in Bangladesh in late 2018. The pest was first detected in China in the southwest province of Yunnan in January 2019 (or June 2019). The fall armyworm was first reported in Southeast Asia in late 2018 in Thailand and Myanmar and its presence is now confirmed in almost all Southeast Asian countries. Oceania In January 2020 S. frugiperda was detected on the Torres Strait Islands, and the Northern Territory, Fall armyworm was first detected in New Zealand in February 2022. Biosecurity New Zealand and sector partners ran a biosecurity response to limit the spread of Fall armyworm and try to eradicate it from New Zealand. This included surveillance and research to better understand the moth, its spread, and potential impacts in New Zealand. By April 2023, it became clear that Fall armyworm was widespread, particularly in the North Island, and that eradication was unlikely because it had been windblown from Australia, and this is likely to repeatedly occur. == Food resources ==

Diet The armyworm's diet consists mainly of grasses and grain crops such as corn, but the species has been noted to consume over 80 different plants (50 non-economic and 30 economic plants). Armyworms earned their common name by eating all plant matter they encounter in their wide dispersals, like a large army. A few sweet corn varieties have partial, but not complete, resistance to armyworms. Cannibalism When possible, larvae will cannibalize the larvae of smaller instars. A 1999 study showed that cannibalism only benefits the caterpillar when other food is scarce. Despite this, the caterpillars will cannibalize others whenever they can, even though it was found to decrease their own fitness in many cases. One known reason why cannibalism is detrimental to the fall armyworm is because of disease transmission to the cannibal. In nature, the negative effects of cannibalism may be balanced by the fact that cannibalism removes competitors, thereby making more resources accessible and indirectly increasing fall armyworms' fitness. == Life history ==

The fall armyworm's life cycle is completed within 30 days during summer, and 60 days during the spring and autumn seasons; during the winter, these caterpillars' life cycle lasts about 80 to 90 days.[3] The number of generations a moth will have in a year varies based on climate, but in her life span a female will typically lay about 1,500 eggs. In warm weather, the eggs will hatch into larvae within a few days. Larva The larvae go through six different instars, each varying slightly in physical appearance and pattern. The larva process lasts from 14 to 30 days, again depending on temperatures. The mature caterpillar is about in length. This is the most destructive life stage as the larvae have biting mouth parts. The larvae have a distinctive inverted Y suture on the forehead. Pupa The larvae then pupate underground for 7 to 37 days in a cocoon they form of soil and silk. Duration and survival of the pupal stage depend on the temperature of the environment. Adults Once emerged, the adults live for about 10 days, and sometimes up to 21 days, with the female laying most of her eggs early in life. Adults are nocturnal and fare best during warm and humid nights. == Migration ==

Adults are capable of flying long distances, so even though they are unable to overwinter north of the southern region of the United States, the moths can migrate as far north as southern Canada in warm months. Their migration rate is remarkably fast, estimated at per generation. Some scientists speculate that this fast migration is aided by the movement of air in weather fronts. == Neurochemistry ==

Allatotropin and allatotropin+allatostatin C – neuropeptides – extracted from Manduca sexta were both found to suppress feeding in all life stages, increase larval mortality, and reduce adult lifespan, by Oeh et al 2000. == Enemies ==

Predators Fall armyworm caterpillars are directly preyed upon by many invertebrates and vertebrates. Common predators include birds, rodents, beetles, earwigs, and other insects. It has been shown that direct predation can cause significant losses to caterpillar populations. Cotesia icipe is another African braconid wasp suitable for the biological control of this lepidoptera. Parasites and disease Fifty-three different parasite species have been discovered in fall armyworm larvae, spanning ten different families. Samples of this were sent to Maree Crawford, the insect pathologist at the Queensland Department of Agriculture for further analysis. This is substantiated by various studies including a 2018 journal article which looked into the effectiveness of N. rileyi had on infestations of armyworms in Indian maize crops. The study concluded N. rileyi could potentially be a cost-effective tool in combating the pest, compatible with eco-friendly management practices, although further studies were required. Farmers in Australia have struggled to control the pest which has been destroying crops, prompting concerns about potential food shortages which could cause an increase in food prices for consumers. The N. rileyi research has given them hope that this can be avoided. == Subspecies ==

The fall armyworm may be presently undergoing a divergence into two separate species. These two strains have major genetic differences that are connected to the plants they feed on, even though both still exist in the same area (sympatric speciation). These two strains can be loosely categorized into a rice strain and a corn strain. This separation is occurring because of differences in habitat (preferred host plant), and differences in reproductive behavior. The reproductive differences can be divided into two categories: difference in the timing of mating at night, and difference in female sex pheromones. == Mating ==

Mate searching behavior and male–male conflict A female attracts males by perching atop the host plant feeding area and releasing a sex pheromone as the signal that she wishes to mate. The pheromone has been studied and found to contain the components Z7-12 and Z9-14. Each female only mates once per night; this creates a physical conflict between the multiple males that will fly towards a ready female. There is an order to which the females call and mate: virgin females do first, females who have mated once next, and females who have already mated multiple times call and mate last during the night. == Interactions with humans ==

Research use S. frugiperda cells (Sf9 and Sf21 cell lines) are commonly used in biomedical research for the purpose of recombinant protein expression using insect-specific viruses called baculoviruses. Vaccine use The Novavax COVID-19 vaccine makes use of baculovirus-infected Sf9 cells to express the SARS-CoV-2 spike protein. For the 2025/2026 influenza season Sanofi used armyworm cell lines and baculovirus to produce Supemtek TIVr, a trivalent influenza vaccine. Pest of crop plants Because of their food preferences, fall armyworm larvae can wreak havoc on a wide range of crops. The first historical account of the fall armyworm's destruction was in 1797 in Georgia. Destruction can happen almost over night, because the first stages of a caterpillar's life require very little food, and the later stages require about 50 times more. Because of this rapid change in food consumption, the presence of larvae will not be noticed until they have destroyed almost everything in as little as a night. The fall armyworm have proved to be a pest in many regions, and methods of control continue to be developed. Africa The fall armyworm was identified in Africa in 2016. In early 2017, armyworms infested large swathes of corn crops across southern Africa, devastating the livelihoods of many farmers. It is thought they arrived as an invasive species from the Americas as eggs in imported produce. This is causing immense concern among agricultural experts, due to the potentially huge amount of damage this invasive species will do to African food crops if allowed to spread. Many African countries have agreed to take urgent actions against armyworms. Sri Lanka After being first reported in India in May 2018 in Tamil Nadu, then the Sri Lankan Ministry of Agriculture issued a warning notice to farmers in the northwestern and north central provinces about possible fall armyworm invasion. At the time of warning, crop destruction had already been reported from the Ampara, Anuradhapura, and Polonnaruwa areas. The larvae are known among the local people as Sena dalambuwa (armyworm caterpillar). Not only corn, but also sugarcane plantations were attacked by the caterpillars in Anuradhapura, Ampara, and Monaragala districts. In December 2018, heavy infestations in corn cultivation were identified. The spread of the moth leads to attack corn all around the country within weeks. At the end of January 2019, the armyworm was present in all districts of Sri Lanka except Nuwara Eliya and Jaffna. On 29 December 2018, armyworms were recorded from paddy cultivations in the Sinhapura area of Polonnaruwa. In January 2019, caterpillars were also recorded from paddy cultivations of the Nochchiyagama area in the Anuradhapura district. The Sri Lankan Department of Agriculture recommended 12 pesticides under three categories, to be used alternately every seven days. Organic farming expert, Thilak Kandegama said that the threat can be overcome by sprinkling rice husk ashes as a repellent. Agricultural Ministry also decided to use drone technology for the spraying of insecticides to control the spreading of caterpillars. == Management and control ==

Because of the fall armyworms' great destructive power, farmers must go to great lengths to deter the larvae. Insecticide is a widely used form of protection; in southern regions, farmers may have to apply insecticide to corn every day. The CABI-led programme, Plantwise and partners have several recommendations for managing fall armyworm, these include: planting early, avoiding staggered planting, and inter-cropping with crops that are not susceptible to fall armyworm, such as cassava or yam. They also recommend conserving shelters and flowering plants on the edges for beneficial insects such as ground beetles and parasitoids. Inter-cropping with the "push-pull" technique with crops such as Desmodium and Napier grass can be used to control fall armyworm. CIMMYT and its partners are using forward genetics to breed for better S. frugiperda resistance in maize. Genome-wide association studies (GWAS) are the most effective method for associating S. f. resistance to the responsible genomic region, especially used in maize/corn but also wheat, sorghum, millet, rice, and legumes. The first uses of conventional breeding in the first decade of the 1900s were reported by Gernet 1917 and Hinds 1914, improving resistance in maize/corn, sorghum, millet, Cynodon dactylon, and Arachis hypogaea. Directorate of plant protection Quarantine and storage, Ministry of Agriculture, Govt of India regularly issues advisories from time to time to manage the menace of Fall Army Worm in India. == See also ==