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Fall Armyworm

 

Spodoptera frugiperda J. Smith - Lepidoptera:  Noctuidae

 

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      This armyworm appears to be indigenous to tropical parts of North America and southern South America.  Overwintering in North America is from south Florida, south Texas and south through Mexico.  Adult armyworms spread out by flying each year

 

 

 

during summer.  However, the species is most damaging in the more humid southeastern United States.  It is suspected that commerce is responsible for its invasion of tropical Africa and warmer parts of Europe.

 

       Dr. John L. Capinera of the University of Florida reported that the life cycle is completed in about 30 days during the summer, but 60 days in the spring and autumn, and 80 to 90 days during the winter.  The number of generations occurring in an area varies with the appearance of the flying adults.  In Minnesota and New York, where fall armyworm moths do not appear until August, there is only a single generation, and more generations further south.

 

       The number of eggs laid in a mass varies from 100 to 200, and total egg production per female averages about 1500 with a maximum of over 2000.  The eggs are sometimes placed in layers, but most eggs are spread over a single layer attached to foliage.  The female also creates a protective layer of scales between the eggs and over the egg mass.  In summer eggs will hatch in two to three days.

 

       Larvae usually pass through six instars.  Young larvae are somewhat green with a black head, but the head color turns to slightly orange by the second instar.  Continued growth displays various light colored spots on a brown body.  Larvae tend to conceal themselves during the brightest time of the day.  Duration of the larval stage averages about 14 days during summer and 30 days during cooler weather (Pitre and Hogg 1983).

 

       Pupation usually is two to eight centimeters in the ground.  The larva constructs a loose oval shaped cocoon 20 to 30 mm in length, by assembling particles of soil with silk.  If the soil is hard, larvae may web together leaf debris and other material to form a cocoon on the soil surface.  The pupa is reddish brown in color, and measures 14 to 18 mm in length and about 4.5 mm in width. Duration of the pupal stage is eight to nine days during summer, but extends to 20 or 30 days during the winter in Florida.  The pupal stage is vulnerable to cold weather (Pitre and Hogg 1983).

 

       Ashley et al (1989), Luginbill (1928) and Sparks (1979) determined that the moths have a wingspan of 32 to 40 mm.  In the male moth, the forewing generally is shaded gray and brown, with triangular white spots at the tip and near the center of the wing.  The forewings of females have fewer markings and are a uniform grayish brown to a fine mottling of gray and brown.  The hind wing is iridescent silver-white with a narrow dark border in both sexes.  Adults are nocturnal, and are most active during warm, humid evenings.  After a preoviposition period of three to four days, the female normally deposits most of her eggs during the first four to five days of life, but some oviposition occurs for up to three weeks.  Adult life may last from seven to 21 days.

 

       The host range is very wide with more than 80 plant species known but grasses are preferred.  The most frequently consumed plants are field corn and sweet corn, sorghum, Bermuda grass, and grass weeds such as crabgrass, Digitaria spp.  When the larval population becomes numerous defoliation tends toward the preferred plants, following which they disperse in large numbers, consuming nearly all vegetation in their path.  Field crops are often injured, including alfalfa, barley, Bermudagrass, buckwheat, cotton, clover, corn, oat, millet, peanut, rice, ryegrass, sorghum, sugarbeet, Sudangrass, soybean, sugarcane, timothy, tobacco, and wheat.  Among vegetable crops, only sweet corn is usually damaged.  Other crops sometimes injured are apple, grape, orange, papaya, peach, strawberry and a number of flowers.  Weeds known to serve as hosts include bentgrass, Agrostis sp.; crabgrass, Digitaria spp.; Johnson grass, Sorghum halepense; morning glory, Ipomoea spp.; nutsedge, Cyperus spp.; pigweed, Amaranthus spp.; and sandspur, Cenchrus tribuloides (Marenco (1992), Pannuti et al. (2015).  Young leaf tissue is most suitable for growth and survival and larvae feeding on the corn kernels show the fastest rate of development (Pannuti et al. 2015)

 

       Many species of parasitoids are known to attack fall armyworm, with the most frequently reared from larvae in the United States being Cotesia marginiventris (Cresson) and Chelonus texanus (Cresson) (both Hymenoptera: Braconidae), species that are also associated with other noctuid insects.  Among fly parasitoids, the most abundant is usually Archytas marmoratus (Townsend) (Diptera: Tachinidae).  Dominant parasitoid species often vary by year and locality (Luginbill 1928) and (Vickery 1929) and (el Heneidy 1985a 1985b).  General predators that attack many other species of caterpillars are found.  Among these are various ground beetles (Coleoptera: Carabidae); the striped earwig, Labidura riparia (Pallas) (Dermaptera: Labiduridae); the spined soldier bug, Podisus maculiventris (Say) (Hemiptera: Pentatomidae); and the insidious flower bug, Orius insidiosus (Say) (Hemiptera: Anthocoridae).  Vertebrates such as birds, skunks, and rodents also consume larvae and pupae readily.  Predation may be quite important, as Pair and Gross (1984) demonstrated 60 to 90 percent loss of armyworm pupae to predators in Georgia.

 

       Numerous pathogens, including viruses, fungi, protozoa, nematodes, and a bacterium have been associated naturally with fall armyworm but populations reductions do not occur.  Among the most important under consideration are the Spodoptera frugiperda nuclear polyhedrosis virus (NPV), and the fungi Entomophaga aulicae, Nomuraea rileyi, and Erynia radicans.  Despite causing high levels of mortality in some populations, disease typically appears too late to alleviate high levels of defoliation.  Among the efforts to obtain other biocontrol agents to reduce the abundance of fall armyworm larvae in corn, only Bacillus thuringiensis presently is showing some promise, with success dependant on having the bacillus on the foliage when the larvae first appear.  (el Heneidy 1985a 1985b).Natural strains of Bacillus thuringiensis tend not to be very potent, but genetically modified strains do improve control (All et al. 1996).

 

REFERENCES:

 

All, J. N.  1988.  Fall armyworm (Lepidoptera: Noctuidae) infestations in no-tillage cropping systems. Florida Entomologist 71:  268-272.

 

All, J. N. ,  J. D. Stancil,  T. B. Johnson & R. Gouger.  1996.  Controlling fall armyworm infestations in whorl stage corn with genetically modified Bacillus thuringiensis formulations. Florida Entomologist 79:  311-317.

 

Ashley, T. R.,  B. R. Wiseman, F. M. Davis & K. L. Andrews.  1989.  The fall armyworm: a bibliography.  Florida Entomologist 72:  152-202.

 

Capinera,  J. L.  2001.  Handbook of Vegetable Pests.  Academic Press, San Diego. 729 pp.

 

El-Heneidy, A. H.  1985a.  Biological aspects on Euplectrus playthypenae How. Hymenoptera: Eulophidae), a larval parasitoid of the fall armyworm, Spodoptera frugiperda J. Smith (Lepidoptera: Noctuidae).  J. Agric. Sci. Mansoura University 10 (4):  1535-1539, Egypt.

 

El-Heneidy, A. H.  1985b.  Influence of host's diet on larval parasitoids of the fall armyworm, Spodoptera frugiperda J. Smith (Lepidoptera: Noctuidae), Cotesia (Apanteles) marginiventris Cress. (Hymenoptera : Braconidae).  J. Agric. Sci. Mansoura University 10  (4):  1540-1543, Egypt.

 

El-Heneidy, A. H. & M. S. El-Dakroury.  1984.  Survey of the lesser cotton leafworm, Spodoptera exigua Hb. associated parasites in maize fields.  Agric. Res. Rev. 62 (1):  347-353, Egypt.

 

El-Heneidy, A. H.,  P. Barbosa  &  P. Gross.  1988.  Influence of dietary nicotine on the fall armyworm, Spodoptera frugiperda and its parasitoid, the ichneumonid wasp, Hyposoter annulipes.  Entomol. Exp. Appl. 46:  227-232, USA.

 

Foster, R. E.  1989.  Strategies for protecting sweet corn ears from damage by fall armyworms (Lepidoptera: Noctuidae) in southern Florida.  Florida Entomologist 72:  146-151.

 

Hassanein, Fawzia A. & A. H.  El-Heneidy.  1984.  On the parasitism of the cotton leafworm, Spodoptera littoralis (Boisd.) on cabbage in Egypt.  Bull. Soc. Ent. Egypte, Econ. Ser., 14:  257-262.

 

Hassanein, Fawzia A. & A. H.  El-Heneidy.  1989.  The parasitism of cotton leafworm, Spodoptera littoralis Boisd. on Jew's mallow, Corchorus olitarius L. in Egypt.  Agric. Res. Rev. 67 (1):  37-42, Egypt.

 

Goergen, G., P. L. Kumar, S. B. Sankung,  A. Togola & M. Tamo.  2016.  First report of outbreaks of the fall armyworm Spodoptera frugiperda (JE Smith) (Lepidoptera, Noctuidae), a new alien invasive pest in west and central Africa.  PLOS ONE, DOI: 10.137/journal.pone.0165632.

 

Johnson, S. J.  1987.  Migration and the life history strategy of the fall armyworm, Spodoptera frugiperda in the western hemisphere.  Insect Science and its Applications 8:  543-549.

 

Luginbill, P.  1928.  The Fall Armyworm. U. S. Department of Agriculture, Technical Bulletin 34: 91 pp.

 

Marenco,  R. J.,  R. E. Foster & C. A. Sanchez.  1992.  Sweet corn response to fall armyworm (Lepidoptera: Noctuidae) damage during vegetative growth.  Journal of Economic Entomology 85:  1285-1292.

 

Mitchell,  E. R.  1978.  Relationship of planting date to damage by earworms in commercial sweet corn in north central Florida.   Florida Entomologist 61:  251-255.

 

Pannuti, L. E. R.,  E. L. L. Baldin, T. E. Hunt & S. F. Paula-Moraes.  2015.  On-plant larval movement and feeding behavior of fall armyworm (Lepidoptera: Noctuidae) on reproductive corn stages.  Environ. Entomol. 45:  192-200

 

Pair, S. D.,  H. R. Gross Jr.  1984.  Field mortality of pupae of the fall armyworm, Spodoptera frugiperda (J.E. Smith), by predators and a newly discovered parasitoid, Diapetimorpha introita.  Journal of the Georgia Entomological Society 19:  22-26.

 

Pitre, H. N. & D. B. Hogg.  1983.  Development of the fall armyworm on cotton, soybean and corn.  Journal of the Georgia Entomological Society 18:  187-194.

 

Roberts, P. M. & J. N. All.  1993.  Hazard for fall armyworm (Lepidoptera: Noctuidae) infestation of maize in double-cropping systems using sustainable agricultural practices.  Florida Entomologist 76:  276-283.

 

Sparks, A. N.  1979.  A review of the biology of the fall armyworm.  Florida Entomologist 62:  82-87.

 

Tumlinson, J. H.,  E. R. Mitchell,  P. E. A. Teal,  R. R. Heath & L. J.  Mengelkoch.  1986.  Sex pheromone of fall armyworm, Spodoptera frugiperda (J. E. Smith).  Journal of Chemical Ecology 12:  1909-1926.

 

Vickery,  R. A.  1929.  Studies of the fall armyworm in the Gulf coast region of Texas. USDA Technical Bulletin 138:  63 pp.