Spodoptera exigua (Hübner, [1808])
Beet Armyworm
 (one synonym : Caradrina pygmaea Rambur, 1834)
ACRONICTINAE,   NOCTUIDAE,   NOCTUOIDEA
  
Don Herbison-Evans
(donherbisonevans@yahoo.com)
and
Stella Crossley


(Photo: courtesy of Ric Bessin, University of Kentucky College of Agriculture)

These Caterpillars are usually green with a pale line along each side, and a dark spot over the second true leg. The caterpillars are an international agricultural pest on crops and pastures, feeding on many plants, including :

  • Lettuce ( Lactuca sativa, ASTERACEAE ),
  • Brussel Sprouts, ( Brassica oleracea var. gemmifera , BRASSICACEAE ),
  • Sugar Beet ( Beta vulgaris, CHENOPODIACEAE ),
  • Soybeans ( Glycine max, FABACEAE ),
  • Cotton ( Gossypium hirsutum, MALVACEAE ),
  • Maize ( Zea mays, POACEAE ), and
  • Tomatoes ( Lycopersicum esculentum, SOLANACEAE ),

    as well as various wild hosts, including :

  • Mallow, ( Malva species, MALVACEAE ),
  • Plantains ( Plantago species, PLANTAGINACEAE ), ad
  • Purslane ( Portulaca oleracea, PORTULACACEAE ).


    (Photo: courtesy of Webshots)

    The caterpillar burrows into the soil below the plant where it pupates with no obvious cocoon.


    (Photo: courtesy of Cathy Powers, Anakle, Victoria)

    The adult moths are brown with a complex pattern including pale kidney-shaped marks on the forewings. The moths have a wingspan of about 3 cms. The pheromones of this species have been identified.


    (Photo: courtesy of CSIRO/BIO Photography Group, Centre for Biodiversity Genomics, University of Guelph)

    The eggs are laid in masses of about 80 and covered in pale scales.

    The species is found world-wide, eg:

  • China,
  • Hawaii,
  • South Africa,
  • U.K.,
  • U.S.A.,

    and over much of Australia including:

  • Western Australia,
  • Northern Territory,
  • Queensland,
  • New South Wales,
  • Victoria,
  • Tasmania, and
  • South Australia.

    Control is being attempted using :

  • Flooding,
  • Pheromone Traps,
  • the virus Nucleopolyhedrovirus ( BACULOVIRIDAE ),
  • the bacterium Bacillus thuringiensis ( BACILLACEAE ),
  • the nematode Steinernema carpocapsae ( STEINERNEMATIDAE ),
  • the ectoparasitic nematode Noctuidonema guyanense ( ACUGUTTURIDAE ), and
  • the wasp Cotesia marginiventris ( BRACONIDAE ).


    drawing by Jacob Hübner, listed as Noctua exigua,
    Lepidoptera IV, Noctuae II, III, Genuinae D etc, Zur Errichtung der Sammlung Europäischer Schmetterlinge,
    Volume 4 (1808), Plate 78, fig. 362,
    image courtesy of Biodiversity Heritage Library, digitized by Ernst Mayr Library, Harvard University.

    Further reading :

    David Carter,
    Butterflies and Moths,
    Collins Eyewitness Handbooks, Sydney 1992, p. 258.

    Ian F.B. Common,
    Moths of Australia,
    Melbourne University Press, 1990, fig. 49.3, pp. 25, 65, 462.

    Jacob Hübner,
    Horde. Phalanx IV. Eulen; Noctuae,
    Sammlung Europäischer Schmetterlinge. Noctuae II,
    Volume 4 (1808), Plate 78, fig. 362.

    Peter Marriott & Marilyn Hewish,
    Moths of Victoria - Part 9,
    Cutworms and Allies - NOCTUOIDEA (C)    ,
    Entomological Society of Victoria, 2020, pp. 12-13.

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    (updated 1 July 2010, 24 January 2023)