This tool is part of the Citrus Resource

Citrus Pests

 

Beet armyworm

 

Scientific name

 

Spodoptera exigua (Lepidoptera: Noctuidae)

Other common names

 

small mottled willow moth, common cutworm

Similar species

 

Larvae of the beet armyworm can be confused with the southern armyworm, Spodoptera eridania. Larvae of beet armyworm and southern armyworm are distinguishable by the presence of a large black spot laterally on the first abdominal segment of the southern armyworm.

Distribution

 

United States: Widespread almost everywhere host plants are grown; overwinters in Arizona, California, Colorado, Florida, Hawaii, Kansas, New Mexico, and Oregon.

Worldwide: Everywhere host plants are grown, most notably Australia, Africa, Southeast Asia, southern England, and Wales.

Native to Southeast Asia.

Diagnostic characteristics

 
Adults
  • Wing span 25 - 30 mm (1 -1.2 in.).
  • Forewings mottled gray brown with irregular banding pattern.
  • Hindwings are usually a uniform white or gray color with a dark line at the margin and a fringe-like border.
  • Soft, scaled wings held around the body when at rest.
Pupae
  • Light brown.
  • 15 - 20mm (0.6 - 0.8 in.) in length.
  • Pupation chamber is composed of sand and soil that is held together with oral secretions.
Larvae
  • 5 larval instars.
  • Early instars are gregarious and later instars are solitary.
  • Pale green or yellow in color during 1st and 2nd instar.
  • Develop stripes in 3rd instar.
  • During 4th instar, stripes get darker.
  • 5th instar is variable, dark dorsally and light ventrally with a white stripe laterally.
  • A series of dark spots or dashes presents dorsally.
  • 25 - 30 mm (1 - 1.2 in.) in the last larval instar.
Eggs
  • Appear circular from above, but from the side, eggs taper slightly at the top.
  • Fine, longitudinal lines.
  • Greenish to white in color.
  • 50 - 150 eggs per mass.
  • Egg masses can be several layers deep.
  • Covered with a layer of whitish scales that give the egg mass a fuzzy appearance.

Hosts

 
Citrus hosts
  • sweet orange, Citrus sinensis
Non-citrus hosts

Broad host range, including weeds as well as vegetable, field, and flower crops. A partial list includes:

  • all cruciferous vegetables, Brassica spp.
  • alfalfa, Medicago sativa
  • asparagus, Asparagus officinalis
  • bean, Phaseolus vulgaris
  • celery, Apium graveolens
  • chickpea, Cicer arietinum
  • corn, Zea mays
  • cowpea, Vigna unguiculata
  • cotton, Gossypium spp.
  • eggplant, Solanum melongena
  • lambsquarters, Chenopodium album
  • lettuce, Lactuca sativa
  • melon, Cucumis spp.
  • mullein, Verbascum spp.
  • onion, Allium cepa
  • parthenium, Parthenium spp.
  • pea, Pisum sativum
  • peanut, Arachis hypogaea
  • pepper, Capsicum annuum
  • pigweed, Amaranthus spp.
  • potato, Solanum tuberosum
  • purslane, Portulaca spp.
  • radish, Raphanus sativus
  • Russian thistle, Salsola kali
  • safflower, Carthamus tinctorius
  • sorghum, Sorghum spp.
  • soybean, Glycine max
  • spinach, Spinacea oleracea
  • strawberry, Fragaria spp.
  • sugar beet, Beta vulgaris
  • Ssweet potato, Ipomoea batatas
  • tidestromia, Tidestromia spp.
  • tobacco, Nicotiana tabacum
  • tomato, Solanum lycopersicum

Host damage

 
Fruits
  • Chew holes and bore into fruit in the later instars.
Leaves
  • Larvae will produce marginal damage on leaves as smaller instars.
  • Can be skeletonized, leaving only the veins.
  • Stems are rarely eaten.

Biology

 

The life cycle consists of 5 instars and can be completed in 24 days. Mating occurs soon after emergence. Oviposition occurs within 2 - 3 days of mating and lasts a week. Adults die within 9 - 10 days of emergence. A female lays 300 - 600 eggs in her lifetime. Eggs are deposited on the lower surface of the leaf, near blossoms, or on the tip of a branch. Eggs hatch in 2 - 5 days in warm weather. Larvae are initially gregarious, eating in groups, but become more solitary as they mature. Larvae can leave silk trails behind them while foraging. Pupation occurs underground.

Overwintering is usually limited to places where frost will not kill the host plant, including the warmer climates of the states in the southeastern and southwestern U.S.

Comments

 

Considered a minor pest of citrus, rarely causing economic damage.

References

 

Atkins, J.R. and E. Laurence. 1960. The beet armyworm, Spodoptera exigua: an economic pest of citrus in California. J. Econ. Entomol. 53(4): 616-619.

Capinera, J.L. 2006. Featured creatures fact sheet: Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Publication EENY-105. University of Florida. (http://entnemdept.ufl.edu/creatures/veg/leaf/beet_armyworm.htm).

University of California, IPM Online. 2008. UC IPM Pest Management Guidelines: Citrus. (http://www.ipm.ucdavis.edu/PMG/r107302111.html).

Authors

 

Weeks, J.A., K.W. Martin, A.C. Hodges, and N.C. Leppla

 

Citrus Pests
Content last updated June, 2012
idtools.org