Introduction and Distribution:
Spodoptera litura is also known as the Oriental leafworm moth, Cluster caterpillar, Cotton leafworm, Tobacco cutworm, Tropical armyworm, Taro caterpillar, Tobacco budworm, Rice cutworm, and Cotton Cutworm. This moth is found in Asia, with some specific problematic pest population reports occurring in Cambodia, Hong Kong, India, the Pacific islands, Guam, American Samoa, and Hawaii. In Australia, it is found in northern two thirds of the country. It is not established in the United States, however, it is a pest of national, regulatory concern.
It has a very wide host range of over 120 plant species, including: lettuce, cabbage, beetroot, peanuts, geranium, cotton, banana, fuchsias, acacia, African oil palm, amaranth, alfalfa, strawberry, sorghum, sugarcane, tomatoes, asparagus, apple, eggplant, beet, beans, broccoli, elephants ear, horsetail she oak, corn, flax, lantana, papaya, orange, mango, leek, among many others.
Adult moths measure between 15-20 mm (0.59-0.79 inches) in length and have a wingspan of 30-38 mm (1.18-1.5 inches). Forewings are gray to reddish-brown, with a complex pattern of creamy streaks and paler lines along the veins. Hind wings are grayish-white with grayish-brown margins. Males have a blue-grey band from the upper corner (apex) to the inner margin of each forewing. Larvae have bright yellow stripes along the back and the sides. Larval color varies from pale green to dark green, and then finally brown for the later instars or more mature forms. Brown, mature larvae appear to have three thin yellow, longitudinal lines: one on the top or dorsal side and one each lateral side. A row of black dots runs along each lateral side, and a row of dark triangles decorate each side of the middle, dorsal line. Field specimens of S. litura may be confused with another exotic species of concern, Spodoptera littoralis, or other Spodoptera species currently occurring in the continental U.S., including southern armyworm (S. eridania), beet armyworm (S. exigua) fall armyworm (S. frugiperda), S. latifascia, yellow-striped armyworm (S. ornithogalli), S. albula, S. androgea, S. dolichos, S. pulchella, and western yellowstriped armyworm (S. praefica). An entomologist may need to closely examine and dissect male genitalia in order to confirm a species identification. Pheromone-based traps are commonly used to detect the presence of various Spodoptera species. As with most moths, Spodoptera adults are nocturnal and not visible during the day.
Females lay eggs in masses of 200 to 300 eggs that are approximately 4-7 mm (0.16-0.27 inches) in diameter and cream to golden brown in color. Egg masses are usually covered with body hair scales and laid on the underside of the host plant leaf. Eggs usually hatch between three to four days. Young larvae or caterpillars are a translucent green with a dark thorax. They are smooth-skinned with a pattern of red, yellow, and green lines, and with a dark patch on the back of the head (mesothorax). Feeding is initially by skeletonizing, or leaving the outline of the leave veins on the plant. As growth continues, caterpillars eat entire leaves, and even flowers and fruits. The Caterpillar burrows into the soil several centimeters and there pupates without a cocoon. While pupating, it produces large amounts of fluid. Attempts to allow pupation in captivity within an empty glass jar have resulted in drowning. The pupal stage lasts either a few weeks or several months in Australia, depending upon time of year. The average life cycle will be completed in about 25 days.
Potential Economic Impact and Description of Damage:
Based on the available geographic records of this moth, it is predicted that 48% of the U.S. will be suitable for survival of this moth. This pest is considered to be of concern from a regulatory perspective. It is believed to have potentially high economic impact in terms of its direct pest damage and trade implications. If you are familiar with typical Spodoptera damage in your area, and you notice unusually high outbreaks or problems on new hosts, consider reporting the problem to your local cooperative extension service for identification support and advice.
Extension specialists or others that strongly suspect they have detected S. litura should contact their local state department of agriculture http://nationalplantboard.org/member/index.html . State and federal (USDA-APHIS-PPQ) regulatory officials may begin quarantine and eradication procedures if a confirmed population is detected.
As S. litura has not established in the continental U.S., local management programs are not available. Remember that any attempt to manage this pest will only occur after regulatory officials have determined that eradication is not possible. The use of Bacillus thuringiensis (BT) may effectively control this pest. Other forms of biological, horticultural, and cultural control that have been studied include: planting near derris and garlic plants, breeding resistant plants from wild plants for example groundnuts from wild groundnuts, breeding resistant plants using bacterium Bacillus thuringiensis genes, using a Baculovirus, using the nematode Steinernema carpocapsae, and using the fly Exorista japonica. For general information on Spodoptera literature, natural enemies, etc. please visit: http://www.aphis.usda.gov/import_export/plants/manuals/emergency/downloads/nprg_spodoptera.pdf
- Capinera, J.L. 1999. Fall armyworm Spodoptera frugiperda (J.E. Smith) (Insecta: Lepidoptera: Noctuidae). Found at: http://entnem.ufl.edu/creatures/field/fall_armyworm.htm
- Capinera, J.L. 1999. Beet armyworm Spodoptera exigua (Hübner) (Insecta: Lepidoptera: Noctuidae). Found at: http://entnem.ufl.edu/creatures/veg/leaf/beet_armyworm.htm
- Capinera, J.L. 1999. Southern armyworm Spodoptera eridania (Stoll) (Insecta: Lepidoptera: Noctuidae). Found at: http://entnem.ufl.edu/creatures/veg/leaf/southern_armyworm.htm
- Capinera, J. L. 2001. Yellowstriped armyworm Spodoptera ornithogalli (Guenée) (Insecta: Lepidoptera: Noctuidae). Found at: http://entnem.ufl.edu/creatures/veg/leaf/yellowstriped_armyworm.htm
- Herbison-Evans, D., and S. Crossley. 2008. Spodoptera litura (Fabricius, 1775). Found at: http://australian-insects.com/lepidoptera/acro/litura.html
- Meagher, R.L., J. Brambila, and E. Hung. 2008. Monitoring for Exotic Spodoptera species (Lepidoptera: Noctuidae) in Florida. Florida Entomologist. 91(4): 517-522. Found at: http://www.fcla.edu/FlaEnt/fe91p517a.pdf
- OZ Wildlife. Armyworm Factsheet. Found at: http://www.ozanimals.com/Insect/Armyworm/Spodoptera/litura.html
- Schreiner, I. 2000. Cluster Caterpillars (Fabricious). Found at: http://www.ctahr.hawaii.edu/adap/Publications/ADAP_pubs/2000-3.pdf
- Silagyi, A. 2006. CAPS Planning Workshop 2006. PowerPoint presentation, found at: http://www.doacs.state.fl.us/pi/caps/images/pdf_caps-workshop_2006.pdf
- USDA-APHIS. 2005. New Pest Response Guidelines Spodoptera. Found at: http://www.aphis.usda.gov/import_export/plants/manuals/emergency/downloads/nprg_spodoptera.pdf
- Venette, R.C., E.E. Davis, J. Zaspel, H. Heisler, and M. Larson. 2003. Mini Risk Assessment: Rice cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae) Found at: http://www.aphis.usda.gov/plant_health/plant_pest_info/pest_detection/downloads/pra/sliturapra.pdf