Overview of Fall Armyworm, Spodoptera frugiperda Jaspreet Sidhu Rangaswamy Muniappan Virginia Tech FALL ARMY WORM TAXONOMY (Spodoptera Genus) • Genus Spodoptera was described by Guenee in 1852 • Genera - Spodoptera, Laphygma and Prodenia - Synonimized • All three combined to form Spodoptera (Bayer,1960) • 25 species are in this genus. FALL ARMY WORM TAXONOMY (Spdoptera frugiperda) • First described in 1797 as Phaleana frugiperda • In 1852, frugiperda was placed in genus Laphygma • In 1958 Laphygma and spodoptera were synonymized Different species in the Genus and their common names • S. eridania :Southern armyworm • S. exigua : Beet armyworm • S. frugiperda : Fall armyworm Prevalent in U.S • S. ornithogalli : Yellowstriped armyworm • S. praefica : Western yellowstriped armyworm • S. exempta : Nutgrass armyworm • S. littoralis : Egyptian cotton leafworm • S. litura : Taro caterpillar • S. mauritia : Lawn armyworm Current distribution of economically important species • S. frugiperda: U.S, South America, Africa • S. littoralis : Africa, southern Europe, Western Arabian Peninsula, Islands of Indian ocean, Islands of Atlantic ocean • S. exempta : Africa, Australia, Hawaii, Western Arabian Peninsula • S. litura : Australia, Pacific Islands, Asia • S. mauritia : Madagascar, Saudi Arabia, Asia, Pacific Islands, Hawaii • S. Exigua: Africa, Western Arabian peninsula, Islands of Indian ocean, Islands of Atlantic ocean Current distribution of economically minor important species • S. pectin: Asia • S. ochrea : Peru • S. marima : Brazil • S. cilium : Africa, Western Arabian Peninsula, Islands of Indian Ocean • S. triturata : Africa Host Plants for each species Species Host Plants S. exempta Poaceae and Cyperacease S. littoralis 44 families including Leguminosae, Solanaceae, Malvaceae, Moraceae, Asteraceae, Poaceae, Chenopodiaceae, and Cruciferae. S. litura Over 100 hosts, including crucifers, legumes, millets, deciduous fruit trees, and various ornamentals and vegetables. S. mauritia Poaceae, Cyperaceae, and Typhaceae S. pectin Poaceae and Cyperaceae S. frugiperda Over 100 host plants but prefers grasses. Spodoptera frugiperda Host Plants • More than 100 plant species • Maize, rice, sorghum, sugarcane, cabbage, beet, peanut, soybean,alfalfa, onion, cotton, pasture grasses, millet, tomato, and potato. • One of most crop damaging pests in the Americas. • In Brazil, annual loss - $400 million. Fall army worm strains • Corn Strain: Maize and sorghum • Rice strain: Rice and turfgrass • Morphologically identical • Distinguished by molecular markers: - Allozyme polymorphisms - Genetic polymorphisms - Mitochondrial haplotyping • Molecular differences are consistent with genetically distinct populations • Differ in susceptibility to chemical and biological agents Maize/ Corn Strain • Florida haplotype profile – Florida and Caribbean population • Texas haplotype profile – Texas through Central America to Argentina • Florida haplotype migrates north up to Canada east of the Appalachian mountains every summer • Texas haplotype migrates north up to Canada west of the Appalachian mountains every summer Fall Armyworm U.S. Infestation and overwintering zone Modified from R. Nagoshi ppt Fall Armyworm U.S. migration Modified from R. Nagoshi ppt Maize and Rice Strains • Both strains occur in Africa • Both strains seem to spread together • Florida haplotype was identified in Togo • Both strains attack maize in Africa INTRODUCTION TO AFRICA (Matthew Cock et al 2017) • It is intercontinental introduction • Might have happened as eggs, larvae, pupae or adults or combinations of these • Possible pathways of introduction: Unaided dispersal ־ Contaminant of a commodity ־ Stowaway on a vector ־ DISPERSAL (Matthew Cock et al 2017) • Unaided dispersal Strong flier, Prevailing trade winds from Americas to Africa do not favor • Contaminant of a commodity • European Union interceptions 2012 – 2016 -17 on Capsicum peppers -11 on other Solanum spp. - 8 on other parts of plants • Minimal trade in fresh produce between Americas and Africa indicates chances of transmission through this route is small DISPERSAL (Matthew Cock et al 2017) • Stowaway on a direct flight More likely • In a 1950 study, of 9000 aircraft from South America and Caribbean to Miami, 98 had lepidopteran eggs • Pre-oviposition female moths could be carried in cargo holds or wheel bays SPREAD WITHIN AFRICA • Unaided dispersal by flight • Through contaminant • Were there multiple introductions? Biology of S. frugiperda Egg mass • Eggs are dome shaped • Dirty white to gray in color. • Laid in groups of about 10-200 eggs per egg mass • Eggs may be laid in a single or in two or more layers progressively superimposed on each other Egg mass • Mostly laid on lower surface of the leaves • Eggs are covered by a layer of grayish scales or hairs giving it a hairy or moldy appearance. • Eggs hatch in about three to five days in summer. Larva • Six larval instars • Fully-grown larvae are 3.1 – 3.8 cm long • Vary in color from pale green to almost black • Three yellowish stripes running down the back • Wider dark stripe and a wavy yellow-red blotched stripe on each side • Predominant white, inverted Y-shaped suture on the head • Larval duration is about 14 days during the summer and 30 days during cool weather Larval Behavior • Initially, newly hatched larvae feed near where the egg mass was laid. • Later, they move up onto the maize plants and consume leaf tissue excluding the veins and midrib. • The larvae exhibit cannibalistic behavior. • Under heavy infestations, the larval densities are often reduced to one or two per plant • Does not undergo diapause • Killed by winter weather Pupa • Pupation normally takes place in the soil at a depth of 2-8 cm. • The pupa is reddish brown in color. • Pupal duration is about eight to nine days during the summer, but may be longer than two weeks under winter conditions • Does not diapause over winter Adult • The adult moths have a wingspan of 32 to 40 mm • Males have dark gray and brown shaded mottled forewings with conspicuous triangular white spots at the tip and near the center of the wing • The hind wing is iridescent silver-white with a narrow dark border in both sexes • Adults are nocturnal, and are most active at dusk for mating • Adults can live up to an average of 10 days but sometimes the duration extends up to three weeks Damage on Maize • Prefers young maize plants • Its attacks all stages of maize plant, foliar consumption is the major factor • Generally feeds on foliage, but during heavy infestations, also feed on maize ears • Foliar damage characterized by ragged feeding, and moist sawdust-like frass near the whorl and upper leaves of the plant • Indirect effects on grain production Damage on Maize • Young larvae feed on one side of leaves leaving the epidermis intact on other side • Older larvae feed by making holes in leaves and eat from the edge of the leaves inward • Larval feeding causes extensive defoliation • Larvae can also burrow into the growing point and affect the growth of plants • Larvae sometimes bore into the ear through the husk and feed on kernels Damage on Maize Economic losses • Outbreaks of Fall Armyworm have been reported in several countries in Africa • Around 330,000 hectares of staple crops, especially maize, have been affected • The remaining African countries remain at high risk. • The severity of the impact on regional crop production is yet to be established Monitoring Often done by using blacklight traps and pheromone traps Pheromone traps are very efficient, suspended at canopy height Insect catches indicate the presence of moths in the area but not good indicators of density Once the moths are detected, search for eggs and larvae To assess the proportion of plants infested, random sampling of 20 plants in five locations, or 10 plants in 10 locations, is considered adequate Chemicals in Pheromone lure • The FAW sex pheromone was reported by Tumlinson et al. (1986) • A mixture of (Z)-9-tetradecen-1-ol acetate, (Z)-9-14:Ac; (Z)-7-dodecen- 1-ol acetate, (Z)-7-12:Ac; (Z)-9-dodecen-1-ol acetate, (Z)-9-12:Ac and (Z)-11-hexadecen-1-ol acetate, (Z)-11-16:Ac • In the ratio of 81: 0.5: 0.5: 18, respectively Companies producing Pheromone traps • ISCA Technologies, California, U.S.A. • Russell IPM, England • Biocontrole • Pherobank • Scentry monitoring products • NovAgrica • Evergreen growers supply • Biocontrol Research Laboratory, Bangalore, India Control methods • Physical control • Cultural practices • Host plant resistance • Biological control • Chemical control • IPM • Handpicking egg masses and larvae • Deep plowing to kill pupae in the soil • Placing sand or ash in the whorls Cultural control • Intercropping with beans has shown to reduce the FAW infestations by 20‐30 percent. (Needs to be tested) (Needs to be tested) Chemical Control • Insecticides main control option: > 25 % plants damaged • Spot treatment for isolated areas effective • Late afternoon or early morning- best time • Recommended insecticides: pyrethroids, carbamates and organophosphates • Granular insecticides for young plants (whorl stage) Chemical Control • Limitations -Concealed larvae -Expensive and not affordable -Appropriate safety procedures may not be implemented on regular basis -Personal protective equipment not available -Increased risk of exposure -Resistance development Insecticide resistance • First noted in 1979, FAW collected from a maize in Tifton, Georgia (U.S.) was shown to be resistant to carbaryl. • In 1991, a strain of FAW collected from maize